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eHam Forums => Amplifiers => Topic started by: KA4WJA on May 28, 2014, 02:31:05 PM



Title: Ham Xcvrs' and Amps', Transmit Spectral Purity, IMD Products, vs. comm/maritime
Post by: KA4WJA on May 28, 2014, 02:31:05 PM
Hello to all....
Instead of piling on and drifting other recent threads (such as the "Alpha/Ten-Tec Merger" and "Filtering Questions", discussions), I thought starting a new topic that is directly on-point might be helpful???

Please remember up front, that I don't have too much spare time (elderly family commitments) to hang out and post messages, so as some of you know, when I do spend the time / make the effort it is probably not frivolous, and well worth the time to read/ponder/comment intelligently on.... :) :)
(but, I still try to keep a sense of humor about these things....after all it's not like good transmit specs are going to save the world... :)

So, here goes...


1)  Over the recent years I've been pleasantly surprised by the well thought-out and somewhat reasoned posts by "Zenki" regarding the lack of concern by hams, radio manufactures, and regulators, of transmitter spectral purity, IMD products, oscil. phase noise, etc. of our radios and amps...

{Aside from his desire for more stringent "gov't regulations" (which I eschew), his thoughts on these matters have paralleled mine....(I'm NOT a convert of his....these are my words / opinions which I've held for years....and the many facts that I'll provide here are all public information available for many, many years...) }

Make no mistake, I also wish that "Zenki" would identify himself/herself, post his/her callsign, etc...
Part of me wishes to ignore/discount anyone who desires to remain anonymous, and I certainly NEVER appreciate "un-named" sources used by media, etc..
I, and many others, are proud of our calls, and have no fear of exposing any of opinions, desires, etc. even our inadequacies, to any/all...
So, I fully understand and accept that "Zenki's" posts are thought of as nuisance to many and as an insult to a few...
Zenki's opinions will mean nothing to me until he mans up and starts posting under his callsign (assuming he has one) like 99+% of the other people here on eHam rather than hiding behind an anonymous screen name.

I totally agree.  I prefer having a conversation with an someone that is not anonymous.  I am proud of my callsign, license and credentials, and wish others were of theirs.

I would think, in an amateur radio forum, having an amateur radio license is a basic credential, and not to much to ask.  

73,

John  W5JON


But, I am NOT him...so maybe my words will be more "appreciated"?? :)




2)  The facts are that there currently ARE "12-volt" HF radios made (w/o any DC-DC converters), that are VERY clean, and are FCC type certified under Part 80, Part 87, and Part 90 (maritime, aviation, and land mobile), as well as meeting CE, ITU, specs/certifications....and this radio here, does excellent service on the amateur radio bands, with full IF-DSP,  vfo, 100's of user-programmable memories, back-lit LCD displays w/ both vfo freq and alpha-numeric info, etc. etc. etc...

This is a current production Icom M-802 HF transceiver, which first entered the market in 2003....and sells for about $1800....(yes, that price is LESS than what some hams think of as "normal", for a full-featured, IF-DSP HF rig....and 1/10 the price of the often bandied-around "$20,000 radio"!!!)

Please have a look at its transmit IMD tests (at 150 watts PEP)...the radio is spec'd at 150 watts output 100% duty-cycle, continuous-duty (FSK/SSB/CW)....

Here are the two "worst-case" transmit IMD spectral scans at 150 watts PEP output...(courtesy of the FCC, note the Part 80, "IMD mask" on the screen)

(http://i43.tinypic.com/2iqeiro.jpg)

(http://i43.tinypic.com/15mxyyp.jpg)


(these are about what the old Yaesu FT-1000 did in Class A....)

You see, there ARE clean "12-volt radios" being made, and they are not that expensive....(oh, and BTW, it meet these specs when operated from 11.5vdc to 15.5vdc....not just at a "nominal" 13.6vdc...)

My problem with Zenki is that he keeps talking about things that are never going to happen.  Yes we would all love a Amplifier or Radio that had a Zenki stamp of approval but that Radio would cost $20,000 and so it will never be made and I so just can't see the point of going on and on about a fantasy radio or amplifier.
 
12-volt based 100w class rigs put out crap on TX. Until buyers start caring about that, nothing will change.

Of course, most won't. The old, what's in it for me deal.


I don't wish to "pick on" anyone in particular (the above quotes are just the most recent ones...sorry), but as you can all see, there ARE clean '12 volt HF radios" being made and selling at "affordable" prices...


And yes, I would also prefer dynamic testing with voice or white noise....but these 2-tone tests are what I have and what are available in the public domain, so that's what I'm stuck with as "facts" here...





3)  And, if any of you are wondering what other specs and design features, this radio has....here are just some of the highlights....
(this is NOT a sales-pitch for this radio, just a run-down of what it is, what it does, and how good the specs are....so that you can all see that this is a REAL radio, that is being used everyday on both the ham and maritime bands, that is NOT outrageously expensive....and has a VERY clean transmitter!!!)

The Icom M-802 is a full IF-DSP based SSB/CW/FSK transceiver (covering 1.6mhz - 30mhz transmit and 500khz - 30mhz rec);   with DSP-based modulation and speech compression;   DBM-input (no rec RF amp);   with full-QSK CW;   a built-in FSK (100-baud) encoder/decoder and simple-display (with adjustable shift spacing and freqs);   AM receive;   secondary/sub-receiver (FSK only);   vfo and memory / channel freq control, as well as direct freq input via the keypad;   DSP-based noise blanker;  Voice Squelch;   DSP-based AGC and DSP-based ALC (no ALC overshoot issues, nor ALC trying to control too much gain, etc.);  memory/channel scan and band scan;  adjustable transmit power level;  adjustable RF Gain;   +/- 150hz RIT;  full computer control capable;  aux outputs and connectors to allow connection/interface to ext. modems, ext. amplifiers, etc.;  full remote control head;   remote automatic antenna tuner interface built-in;   etc. etc.
(yes, it lacks some "features" that some hams desire...and has features that no ham needs.....but I'm NOT advocating that this is a replacement for our ham transceivers, just pointing out all the features/specs this radio has, for the 'affordable" price of $1800...)


--- The M-802's first IF is at 64.455mhz, where there is a first IF crystal filter (nowadays called a "roofing filter") of 15khz wide.

--- The M-802's second IF is at 455khz, and there is a 2nd IF ceramic filter of approx. 12khz wide. (note that ceramic filters at 455khz perform very well)

--- The M-802's third IF is at 12khz, and here is where the DSP module does all the work of mode filtering, demodulating various modes, etc.

From the M-802's serv manual...
Quote
The DSP [Digital Signal Processor] circuit enables digital IF filtering, digital noise reduction, digital PSN [Pulse Shift Network], phase demodulation, digital automatic notch, etc.   As well as does all the "modulating" and "speech compressing" during transmission.

The few receiver tests specs I have, show a wide-spaced IMD3 of 100db, narrow spaced IMD3 of >80db, BDR of 142, and phase noise 134-135dbc/hz....making better than most "ham radios" costing 2 - 3 times as much$$$$....

(The M-802 has a great receiver, which outperforms probably > 99% of the "ham" transceivers out there, including many that cost 2 - 3 times the price!!
It doesn't have phase noise issues like many modern $3000 - $5000 ham rigs have, and hence doesn't suffer from noise-limited IMD...it does not suffer from recip mixing IMD, etc.)


As the M-802 is designed (both hardware and firmware) to conform to the FCC Part 80, 87, and 90 standards, therefore there is no feature for changing any of the transmit filtering....
And, in receiving (all IF-DSP controlled):
--- the SSB voice bandwidth is controlled at 2.4khz wide....
--- the AM voice bandwidth is 6khz (I think??)
--- the CW and FSK-Narrow (F1B) and AFSK-narrow (J2B) bandwidth is 500hz...

--- the AFSK/J2B-middle bandwidth is 1khz...
--- the FSK/F1B-wide bandwidth is 1khz...
--- the AFSK/J2B-wide bandwidth is 2.4khz...

Additionally it furthers has 3 "digital mode" filter bandwidths are:
--- narrow is 500hz...
--- middle is 2.4khz...
--- wide is 2.8khz...

http://www.icomamerica.com/en/products/marine/ssb/m802/

http://www.docksideradio.com/Icom%20SSB%20Radios.htm


And again, this radio is spec'd at 150 watts output, 100% duty-cycle, continuously duty (FSK/SSB/CW).....
And again, here are the transmit spectral scans (from the FCC certification test report)...

(http://i43.tinypic.com/2iqeiro.jpg)

(http://i43.tinypic.com/15mxyyp.jpg)




Compare those to a brand new, fresh out-the-box, Icom IC-706MkIIG....(courtesy of the ARRL lab)
(http://i44.tinypic.com/esoidy.jpg)


And, how about the $3500+ Elecraft K3.....anyone wish to agree that this transmitter can be thought of as "total garbage"??? (courtesy of NC0B, Rob Sherwood)
Sorry guys....I know there are many "militant" K3 supporters here, and I'm not trying to antagonize you...but Rob Sherwood uses this in his regular presentations, so it should not be a surprise, nor is there any controversy here....the K3's transmitter is what it is....(they market / hype the receiver, not the transmitter...)

(http://i60.tinypic.com/2jeo3s5.png)



Without actually seeing the real transmitter IMD test scans of the real commercial/marine "12-volt dc" radio (the Icom M-802), and without reading the specs/features of this same reasonably "affordable" radio ($1800, for the M-802), I understand that some would jump to the conclusion that "it can't be done at 12 volts", and/or "it's too expensive", etc...
But, with all this information I posted here, I think you can all see that these conclusions / reactions are misplaced, and it CAN be done easily and at a relatively low cost...
BUT...

But, even more impressive is the fact (sorry I don't have the scans to "prove" it) that a couple older "12 volt" HF marine transceivers, have even BETTER transmit spectral purity and even lower transmit IMD products....
Such as the Icom M-700Pro (which is a 1990's design, that just ceased production about 7 - 8  years ago, and retailed for ~ $1250...and can be purchased used nowadays for about $500 - $700) had even lower phase noise, and all IMD products down better than 75db...and here again, this is at 150 watts PEP output continuous-duty (FSK/SSB/CW)..
Yes it did have a full vfo as well as 150 channels, etc....but not too many "ham-radio-type features".....but its "12 volt PA" and its entire transmitter was VERY clean...(actually better than a Yaesu FT-1000 in Class A)



....Continued in next post....

73,

John,  KA4WJA
s/v  Annie Laurie,  WDB6927



{P.S.....BTW, I'm not one that thinks someone must disclose their credentials and/or brag about their experiences, in order to present facts....and I don't believe any of us should need to un-zip and break-out a yardstick to see who is "the most qualified"... :)
But, just an FYI....yes, I'm a bit younger than many of you (53) and was licensed as a teenager...majored in physics, but have run my own electronics firm for the past 30 some years....but, most importantly I have operated and installed numerous HF maritime radios on-board many vessels since the early 1970's (a few years before becoming a ham, 35 years ago...)
(as I'm NOT an RF engineer by trade or education, I defer to those of you here that are....but, I DO understand the radios, the various circuitry, and most importantly the real-world problems that poor transmit spectral purity is causing!!)
And still to this day, I regularly operate on both the maritime and ham bands on-board, when at sea and/or tied to the dock...so, in addition to the above facts, I have real world, first-hand experience with the best and the worst of HF transmitters... :) }


Title: RE: Ham Xcvrs' and Amps', Transmit Spectral Purity, IMD Products, vs. comm/maritime
Post by: KA4WJA on May 28, 2014, 02:33:27 PM
Continued from above...

4)  And, since this IS the "Amplifiers" Forum....in regards to how some (many??) hams might feel an amp with good IMD specs might be wasted money....
(Minor Opinion Alert Here!)
[when discussing average exciter IMD] Anything over that in an amplifier is wasted money. Your amplifier IMD is set by the driver radio. Most tube amplifiers and even tetrodes have an IMD of better than 42 dB. My 8410 measured 43 minimum on all bands.

Now put on your marketing hat and try to market an amplifier with the best IMD possible. Hams want cheap reliable power, and good resale ownership.   Everything else is wasted money.  You are promoting the attributes of a fine Merlot to an audience with a beer budget.
I have great respect for your RF design expertise Mike, but here we disagree!!!

If we say that the radios could be better, but the amps are "good enough"...or vice versa, that the amps need to be better, but the radios are "pretty good"...aren't we just promoting self-fulfilling prophecies???
I think so...but, others may have different (valid) opinions..
(I'm not even going to bring up the "all knobs to the right" / "drive every watt possible out of it", philosophy of so many hams these days....'cause it'll just cloud the main issue here, that we as ham consumers CAN demand better transmit spectral performance from the manufactures, and the manufactures CAN make "affordable" radios and amps that provide these better specs...)

But, back to some facts...
Ever seen the results of a really clean transmitter into a really clean amp???
Here is the result of an FT-1000MkV in Class A, into an Alpha 77, running about 2000 watts PEP....and using a transceiver such as the above mentioned M-802 or M-700Pro, would have similar (or even better) results...
(I know that the FT-1000 has some other issues, such as its ALC-induced issues, but here I'm just using this as an example to show the static transmit IMD results....and I'm limited by the spectral scans that I have and that are out in public domain...)

Have a look...
(http://i61.tinypic.com/2hh0phu.png)


Anyone have a scan of a K3 into a ALS-600, etc.???
Anyone need to see one in order to know how crappy the signal is??  :)





5)  Also, I've been confused by the knee-jerk reactions and/or off-the-cuff comments about marine radios not being designed to meet modern ham standards or the needs/desires of the modern ham operator....
As someone who actually operates on the marine bands very regularly (and have for 40 years now), perhaps I can clarify things a bit...

--- I am NOT advocating that all hams should use marine HF radios...
--- But rather pointing out that the same designers, engineers, and factories that are making our HF ham transceivers with truly HORRIBLE transmit spectral purity and "total garbage" transmit IMD specs/tests, are also designing/engineering/manufacturing hi-quality "12 volt" HF transceivers at reasonable prices, that have excellent transmit purity and specs!!
--- And, I'm wondering (and posing the question here), WHY are so many hams accepting this, and not demanding better???





6)  Further, there is some misinformation here...(sorry Mike)....
This is only a problem with HAM radio. We are the only radio users that butt transmissions right up against each other. Marine and Aviation users are on 25 KHz split frequencies. Their radios are not any cleaner but the neighborhood is much more sparse.
Actually the Marine channels DO butt right up against each other...they are 3khz wide...(hence the need for 2K80J3E emissions and VERY clean transmitters!)
And YES these adjacent channels ARE used, so keeping splatter at bay is important here...

Just so we fully understand things, I'm going to give real world, personal examples...
--- Over the years (and as recent as last week), I have run or assisted on Maritime HF Nets and Weather Broadcasts...

--- For long-range offshore weather, I regularly use 12.359mhz for over an hour each day, and always have other weather broadcasts (w/ 1000-watt transmitters) transmitting on 12.362mhz and 12.365mhz simultaneously...(during my broadcasts/net)
(and, occasionally have other traffic on 12.353mhz and/or 12.356mhz, as well...)

--- For more regional offshore weather, I regularly use 8.294mhz...and just as regularly have other traffic on 8.297mhz...(as there are only two worldwide 8mhz simplex maritime Voice channels) BUT....

--- But, even more importantly when using 8.294mhz, we must be conscience of the fact that 8.291mhz is the 8mhz Int'l GMDSS Distress Calling Frequency....and causing interference there just isn't "bad engineering practice", but can actually cost someone their lives!!! (just this past week 4 mariners died/drown in the N. Atlantic, 1000 miles ESE of Cape Cod....while two other groups of 3 each, were successfully rescued in the N. Atlantic all in just the past 7 - 10 days...and this stuff happens all the time....so, NOT causing interference IS very important!!)

--- I immediately know when someone on an adjacent channel is using a "MARS-modified" / "opened-up" ham radio on the marine freqs....as their splatter is truly horrible!!
(I can spot an IC-706, from 1000's of miles and 10khz away!! :) )
And, don't forget that many maritime mobile service radios are not supplied with a regulated 13.6 - 13.8vdc...but, rather many are operated at voltages as low as 12 volts, or even lower in some situations (especially in emergencies)....
Anyone ever heard/measured a "modern 12-volt ham transceiver" operated on low voltages such as 11.5 - 12.5 volts???  (once you hear the "fm'ing" and other distortions "in-band", you'll never forget it....and if you tune a few kHz up/down, you'll quickly see just how much crap is being transmitted outside the transmitters passband!!!)

--- In years past (before sat comm became more affordable), there was a tremendous amount of HF voice activity all hours of the day/night on almost all the HF Maritime freqs (both simplex and duplex), especially crowded with "public correspondence" (ship-to-shore radio-telephone calls)...
And, the ITU tried to assigned the coast stations their channels that would have some sort of "buffer" (typically a one or two channel width buffer, of 3khz or 6khz) between stations that would be within single-hop or double-hop range of each other and their primary customers at sea...in order to reduce de-sense and any problems with splatter coming from 1000 watt ship stations and 10,000 watt shore stations...
Even today, with less number of users, there are still 3 - 6khz spaces between the coast stations' assigned channels...)
BUT...
But, this is NOT the case for the simplex ship-to-shore, and ship-to-ship channels that are all stacked right next to one another, ever 3khz....

--- I won't ramble on and on about this, as this is a fairly innocuous point, which distracts from the main issue that ham radio transmit spectral purity and IMD products are truly Horrible and other radio services using the HF bands (such as the HF maritime mobile radio service) requires much stricter specifications, and the radio manufactures comply with these rules, producing "12 volt" radios at reasonably "affordable" prices..


Sorry Mike, but the facts are:
a)  the HF marine radios ARE much cleaner!!!
 ---  and ---
b)  the marine HF channels ARE only 3khz wide, and adjacent channels ARE used quite regularly!!!






7)  How about I leave you all with some good (but sobering) thoughts???
Mike, here I agree with you and can commiserate!!! (still amazes me that even seasoned hams run their RF wide open on every band, at all times!!)
 
Your radio can be as clean as a whistle but due to signal strength, poor receiver design, NB on and operator error at the other end they will perceive that you are splattering. I would guess most hams have no idea what the RF gain control is used for.

About 6 years ago at Dayton, I help set up the special event station. We were at the ICOM booth running a 7800 and an amplifier (1000 watts) to a 4 element SteppIR beam at 80 feet. All day long everyone with a mobile in the parking lot would come in to tell us about our wide signal. I’d ask how strong we were and the regular reply was we were pinning their S meter. As soon as I explained about receiver overload their eyes would glaze over.
The problem is, if all we do is accept the status quo, things will get worse and worse....and we will all have nobody to blame but ourselves...


And, this sums up the REAL point of all my ramblings here today...
In regards to our HF bands, interference, distortions, transmitter spectral purity, etc..
Alternatives DO exist...
--- and ---
They are reasonably "affordable"

Isn't up to US to try to make things better???


How about we all write Icom Kenwood, Yaesu, TenTec, Flex, etc. etc. etc....and request that they actually make HF ham transceivers that meet these specs, and fit inside this "mask"???
(http://i61.tinypic.com/231pi1.png)




Okay, enough for now....(I've actually got other things to do..:)


73,

John,  KA4WJA
s/v  Annie Laurie,  WDB6927





{P.S.....BTW, I'm not one that thinks someone must disclose their credentials and/or brag about their experiences, in order to present facts....and I don't believe any of us should need to un-zip and break-out a yardstick to see who is "the most qualified"... :)
But, just an FYI....yes, I'm a bit younger than many of you (53) and was licensed as a teenager...majored in physics, but have run my own electronics firm for the past 30 some years....but, most importantly I have operated and installed numerous HF maritime radios on-board many vessels since the early 1970's (a few years before becoming a ham, 35 years ago...)
(as I'm NOT an RF engineer by trade or education, I defer to those of you here that are....but, I DO understand the radios, the various circuitry, and most importantly the real-world problems that poor transmit spectral purity is causing!!)
And still to this day, I regularly operate on both the maritime and ham bands on-board, when at sea and/or tied to the dock...so, in addition to the above facts, I have real world, first-hand experience with the best and the worst of HF transmitters... :) }


Title: RE: Ham Xcvrs' and Amps', Transmit Spectral Purity, IMD Products, vs. comm/maritime
Post by: K2GWK on May 28, 2014, 03:47:45 PM
The few receiver tests specs I have, show a wide-spaced IMD3 of 100db, narrow spaced IMD3 of >80db, BDR of 142, and phase noise 134-135dbc/hz....making better than most "ham radios" costing 2 - 3 times as much$$$$....

The $1000 Elecraft KX3's Receiver outperforms the Icom M-802'a Receiver as does the $1600 Kenwood TS-590S.

http://www.sherweng.com/table.html (http://www.sherweng.com/table.html)

I will be honest with you. You will never get the manufacturers to change when the products they have designed are within the FCC's spec of 30dBc for 3rd order IMD. Now if you were to get the FCC to change the spec to 40 dBc or better you would see the manufacturers scramble to get something done almost overnight.


Title: RE: Ham Xcvrs' and Amps', Transmit Spectral Purity, IMD Products, vs. comm/maritime
Post by: KA4WJA on May 28, 2014, 04:16:56 PM
Guy,
Yes, we can always find some radio that does something better, even for less money....
(and I'm now regretting even mentioning rec specs, as this seems to be clouding the issue... :)

My intent is/was not to try to say that this particular radio is so great, etc., nor that anyone should buy/use this particular radio....rather to use this radio as a example of what is currently available as a "12-volt" 150-watt HF radio, that is reasonably "affordable", and that has excellent transmit specs...


BTW, I do like the KX3....but isn't the KX3 a 10-watt radio??
(not that there is anything wrong with QRP, but this is "Amplifiers" forum)  :) :)





While I'm not naïve, and fully grasp the battle that would be needed, I'm not sure others grasp that the radios are already being made, it's just they'd need to be slightly "redesigned" with different firmware and controls....
Think of the IC-7800 front panel / knobs / display / interfaces....driving the M-802's guts....sell if for 1000's of dollars, make everyone happy???
(yeah, a pipe dream...I know that....just trying to spur some thought about this topic, out in the open, not anonymously...)  :)
 


73,
John,  KA4WJA


Title: RE: Ham Xcvrs' and Amps', Transmit Spectral Purity, IMD Products, vs. comm/maritime
Post by: KI6LZ on May 28, 2014, 04:21:29 PM
Perfectly clear to me what John's point is, along with pictures too. :)


Title: RE: Ham Xcvrs' and Amps', Transmit Spectral Purity, IMD Products, vs. comm/maritime
Post by: K2GWK on May 28, 2014, 04:29:31 PM
Guy,
Yes, we can always find some radio that does something better, even for less money....
(and I'm now regretting even mentioning rec specs, as this seems to be clouding the issue... :)

My intent is/was not to try to say that this particular radio is so great, etc., nor that anyone should buy/use this particular radio....rather to use this radio as a example of what is currently available as a "12-volt" 150-watt HF radio, that is reasonably "affordable", and that has excellent transmit specs...


BTW, I do like the KX3....but isn't the KX3 a 10-watt radio??



73,
John,  KA4WJA


Quote
I will be honest with you. You will never get the manufacturers to change when the products they have designed are within the FCC's spec of 30dBc for 3rd order IMD. Now if you were to get the FCC to change the spec to 40 dBc or better you would see the manufacturers scramble to get something done almost overnight.

Yes it is and I am sure that the 3rd order IMD even at 10 watts is in the 30dBc range. I am not saying Zenki is wrong. I just think he is placing blame on the wrong party. Of course the manufacturers have it within their power to design and build an amplifier that is much better than 30dBc 3rd order IMD. The point I am trying to make is that the Manufacturers (Kenwood, Yaesu, Icom, Elecraft and TenTec) will keep designing their products to meet the 30 dBc FCC spec until the FCC decides to change the spec. There is no incentive for the manufacturers to change until the FCC changes the spec. Maybe instead of Zenki attacking the radio manufacturers he should be holding the FCC responsible for their poor spec limit. Maybe we can get the ARRL to put pressure on the FCC to change the spec if the splatter caused by an amplifier that barely makes 30 dBC 3rd order IMD is becoming a major issue.



Title: RE: Ham Xcvrs' and Amps', Transmit Spectral Purity, IMD Products, vs. comm/maritime
Post by: K2GWK on May 28, 2014, 04:38:01 PM
Perfectly clear to me what John's point is, along with pictures too. :)

Me too!! Read my post above.....


Title: RE: Ham Xcvrs' and Amps', Transmit Spectral Purity, IMD Products, vs. comm/maritime
Post by: KI6LZ on May 28, 2014, 04:50:10 PM
I've stared at too many govt specs. All a manufacturer has to do is comply with the spec and nothing more. Heck, we're now getting radios better than spec.


Title: RE: Ham Xcvrs' and Amps', Transmit Spectral Purity, IMD Products, vs. comm/maritime
Post by: KA4WJA on May 28, 2014, 05:37:37 PM
BTW, in case anyone is wondering, I use an Icom M-802 daily....(I own 2 of them)
But, I still prefer either of my old Drake TR-7's for casual ham operating at home....



But, Icom is NOT the only player here!!!

Here are some other current production and recently discontinued commercial / maritime HF transceivers (all "12 volt" radios)

--- Yaesu / Vertex still has a current production radio that meets these specs/standards....the VX-1700 HF/SSB (which replaced the older, but VERY clean FT-600 / ""system 600")

--- Kenwood still makes their TRC-90 HF-SSB certified for land mobile, etc...(but unfortunately no longer makes their HF marine TKM-707..)

--- Other manufactures, such as Furuno, SEA, Thrane & Thrane / Skantic / Sailor, etc. have all made fully ITU and FCC Part 80 compliant radios , "12 volt" 150 watt output radios ....(as well as 24 volt versions w/ 250-watt, 500-watt, 800-watt, or 1000-watt PA's...)



Just didn't want anyone to think this was an "Icom only" thing....  :)



73,
John,  KA4WJA
 


Title: RE: Ham Xcvrs' and Amps', Transmit Spectral Purity, IMD Products, vs. comm/maritime
Post by: KH6AQ on May 28, 2014, 05:46:45 PM
Very good points on transmitter IMD and the possibilities for amateur service.

Looking at the IC-802M marine transceiver service manual, the 12 volt PA design looks (to me) much like a PA designed for the amateur market. However, the bipolar transistors are SD1487 type, with the datasheet showing operation beyond 150 watts in single-ended service. Comparing the IC718 amateur transceiver PA, it uses the RD70HHF1 MOSFET, with the datasheet showing it running out of steam at 60 watts in single-ended service.

  



Title: RE: Ham Xcvrs' and Amps', Transmit Spectral Purity, IMD Products, vs. comm/maritime
Post by: KA4WJA on May 28, 2014, 06:01:58 PM
Guy,
Okay, I think now I understand your comments....
You and I are in agreement that Zenki was placing the blame on the wrong parties (the manufacturers), rather than where I place the blame (on us hams, that accept the status quo)..or where you seem to placing the blame (on the FCC spec ???)




I think you and I will simply need to politely agree-to-disagree here....
I am not saying Zenki is wrong. I just think he is placing blame on the wrong party. Of course the manufacturers have it within their power to design and build an amplifier that is much better than 30dBc 3rd order IMD. The point I am trying to make is that the Manufacturers (Kenwood, Yaesu, Icom, Elecraft and TenTec) will keep designing their products to meet the 30 dBc FCC spec until the FCC decides to change the spec. There is no incentive for the manufacturers to change until the FCC changes the spec. Maybe instead of Zenki attacking the radio manufacturers he should be holding the FCC responsible for their poor spec limit. Maybe we can get the ARRL to put pressure on the FCC to change the spec if the splatter caused by an amplifier that barely makes 30 dBC 3rd order IMD is becoming a major issue.
In my opinion, the market CAN and DOES enforce changes...and if we try harder, we do NOT need further FCC rules/regs/standards....


If we (hams) actually desire better transmitters (I think this is pretty much a "no-brainer", but others may disagree...), then it is up to us, the amateur radio operators / consumers to "demand" better transmitters (by NOT buying the crappy ones!)....

Again, I'm NOT naïve....I realize this is an extremely difficult goal to achieve...
But...

But, perhaps if the ARRL could be made to publish BIG pictures comparing the transmitter spec / spectral scans of all these radios, especially highlighting the excellent results from other radios made by the SAME manufacturer....then maybe we have a chance!!!
(I joined the ARRL in March of 1974.....and except for a year of lapse, I've been a member for 40 years!!!  Maybe we could get 10's of thousands of ARRL members to "vote" with our dollars / membership dues???)

This, could then be used to have the "vast ham universe" :) , force change....by again voting with our $$$$....





73,

John,  KA4WJA
s/v  Annie Laurie,  WDB6927


Title: RE: Ham Xcvrs' and Amps', Transmit Spectral Purity, IMD Products, vs. comm/maritime
Post by: KI6LZ on May 28, 2014, 06:12:03 PM
It would be nice to see transmitter IMD plots in their ads instead of Ip, DR, BDR, etc. Seems like they are battling it out in the receiver area way past noticeable improvement, somehow we need to steer them toward transmitter improvements and probably the last way is trying to change the specs.


Title: RE: Ham Xcvrs' and Amps', Transmit Spectral Purity, IMD Products, vs. comm/maritime
Post by: KM3F on May 28, 2014, 07:16:17 PM
It will be a few more years until the mfgers can get the designs worked out but this whole IMD thing is about to change.
It has already been achieved at more than 60 down on the third and brick walled bandwidths.
Look for it in the Flex and ANON radios as soon as the hardware and software is finalized.
I suspect the KW990 may even be capable as soon as it can be implemented with software and supporting hardware.
What you may hear in the future, while on the air, is some op telling you to get a new radio because his built-in spectrum analyzer sees your signal as dirty under it's present design through no fault of yours.
I bet some of you will like to be told that!
Good luck.


Title: RE: Ham Xcvrs' and Amps', Transmit Spectral Purity, IMD Products, vs. comm/maritime
Post by: KA4WJA on May 28, 2014, 08:14:21 PM
Ken,
I'm afraid I'm not up-to-date with what future developments Flex and ANON might be working on....(thanks for the heads-up, I'll look into it...)

But, the point I'm trying to make is, there ARE currently full-featured, HF transceivers, that provide excellent service on the ham radio bands, that have excellent transmit spectral purity and extremely low IMD products, with the IMD products that actually cause most of the splatter (5th and higher order products), completely non-existent....
And, these radios are now currently on the market (and have been for years), at a reasonably "affordable" price...(< $2000)
The manufacturers are already making these radios and selling them for $1000 - $1800 retail....nobody needs to wait until some software engineer works out kinks in some $10,000 radio...

 

Again, I appreciate the info on what Flex and ANON might be developing...
But...Why should hams "wait 'n see what's coming out next year"?
It will be a few more years until the mfgers can get the designs worked out but this whole IMD thing is about to change.
It has already been achieved at more than 60 down on the third and brick walled bandwidths.
Look for it in the Flex and ANON radios as soon as the hardware and software is finalized.
I suspect the KW990 may even be capable as soon as it can be implemented with software and supporting hardware.
This is a problem that has an easy and currently-available solution....perhaps too many hams are believing marketing hype or "Dayton-speak"?
I'm not sure....

But again, my point is that ARE radios available NOW, at reasonably "affordable" prices,  designed and built by the same guys that are building the ones with poor transmitter specs...
And, I'm asking the questions....

Are hams just too complacent?
Are we all sheep?
Or, are most hams just bowing to "peer pressure"?
(Or, horror of horrors, are many just happily ignorant?  I hope not!!)

So, instead of everyone trying to assess blame, or praise what future radios may be coming....perhaps we can all collectively "demand" better radios now....by simply NOT buying anything (NOTHING at all) from any company that ignores this problem and simply tries to sell crappy transmitters!!!






This would be fine with me!!!
What you may hear in the future, while on the air, is some op telling you to get a new radio because his built-in spectrum analyzer sees your signal as dirty under it's present design through no fault of yours.
I bet some of you will like to be told that!
Good luck.
I always give "honest" signal and audio reports....and while some are insulted, most appreciate it!!!
So, this would be fine with me....

 


73,

John,  KA4WJA


Title: RE: Ham Xcvrs' and Amps', Transmit Spectral Purity, IMD Products, vs. comm/maritime
Post by: KM3F on May 28, 2014, 09:22:33 PM
I occasionally look at the ARRL IMD test results on many radios they test and not impressed.
A lot of the IMD problem is driving amplifiers into distortion or mis adjustment of same.
The RMI line of 12 volt amplifiers are a case in point.
They are not test accepted here in this country operated as they spec them for.
The 300P is mfger rated to 500 + ' horsepower' for 12 volt devices and not good for IMD.
Just recently I monitored the use of one of these 300P amps and see it has some extra 'artifacts' on the outer edges, off frequency so it's not as clean as it should be.
This amplifier really is no worse than the KW480HX that is rated at 200 watts.
The difference is KW limits the drive and output to it's reasonable linear range instead of allowing the final stages to be driven all out and cause a lot of havoc on the bands plus reputation degradation which they don't need.
The coming IMD control involves feeding back an output sample, shifting phase, delaying and some filtering to cancel distortion to a low level..
While not perfect, it is a quantum leap in the IMD cleanup process.
If a new line of devices were to be developed and circuits designed around them, the IMD could become quite low.
I have been monitoring this discussion and applications by very knowledgeable people on the air and done research on the subject, finding is has been worked on as far back as the late 90s.
It's just now filtering into the present day application.
Good luck.


Title: RE: Ham Xcvrs' and Amps', Transmit Spectral Purity, IMD Products, vs. comm/maritime
Post by: K6AER on May 28, 2014, 09:59:54 PM
All of the 3rd order/IMD discussion is a moot point when the radios being used on the ham bands are older than 20 years. Hams  not going to swap out there trusted radio for 10 dB less spectral noise anymore than the family dog will get put down for oopsey on the  carpet.

Most radios will work just fine if the last ten % of power is not sent up the coax. Yes there are better radios for spectral purity but if you only running 100 watts into a dipole chances are you IMD is lost in the band noise floor.

Where spectral purity and adjacent channel frequency noise comes into play is when have a large beam up high with an amplifier. Now your 30-40 dB stronger and all the dirty laundry is out for all to see.
 
The real question is how much are you willing to pay for 15 dB cleaner signal? I will bet most hams would not spend 5% more on their radio. This is amateur radio and where do you draw the line between experimentation and nanny state overreach to a perceived issue.

I wonder how many hams who worry about IMD so much, actually spend any time on the air. I figure if they don't have a call we can eliminate a lot of postings.


Title: RE: Ham Xcvrs' and Amps', Transmit Spectral Purity, IMD Products, vs. comm/maritime
Post by: KA4WJA on May 28, 2014, 10:09:16 PM
Ken,
Is this not just "pre-distortion" or "negative-distortion", that has been employed for many years (20 years) now?
Or are some folks working on something new?
The coming IMD control involves feeding back an output sample, shifting phase, delaying and some filtering to cancel distortion to a low level..
While not perfect, it is a quantum leap in the IMD cleanup process.
If a new line of devices were to be developed and circuits designed around them, the IMD could become quite low.
I have been monitoring this discussion and applications by very knowledgeable people on the air and done research on the subject, finding is has been worked on as far back as the late 90s.
It's just now filtering into the present day application.
If this is the former (pre-distortion), it's been with us for quite some time, and I'm not sure what new devices are needed....and I'm not sure I'd call it a "quantum leap"....

So, I assume there is something new that I'm not aware of, coming down the pike?
Please tell us..


73,

John,  KA4WJA





Title: RE: Ham Xcvrs' and Amps', Transmit Spectral Purity, IMD Products, vs. comm/maritime
Post by: KI6LZ on May 28, 2014, 10:33:03 PM
My understanding is that this pre-distortion is now starting to be implemented in DSP coding. Nothing more, nothing less.


Title: RE: Ham Xcvrs' and Amps', Transmit Spectral Purity, IMD Products, vs. comm/maritime
Post by: KA4WJA on May 28, 2014, 10:55:39 PM
Mike,
As I wrote earlier, I have a great deal of respect for your RF engineering knowledge...but, I think you may have missed the point (sorry, my fault for such long rambling posts)....


Perhaps you missed the part where the radios are NOT more expensive?  
The real question is how much are you willing to pay for 15 dB cleaner signal? I will bet most hams would not spend 5% more on their radio.

(and depending on what radio you're comparing them to, are LESS expensive)
But, regardless....I AM willing to pay more and there are others out here like me...





Yes, I use my 35 yr old TR-7, when at home....and some of my friends also have some older radios, but most of the stations I work are all using fairly new / "modern" radios (made within the past few years...)  
All of the 3rd order/IMD discussion is a moot point when the radios being used on the ham bands are older than 20 years. Hams  not going to swap out there trusted radio for 10 dB less spectral noise anymore than the family dog will get put down for oopsey on the  carpet.
Yes, there are a lot of old radios out there....but years ago there were a lot of old cars (w/o air bags, or even shoulder straps) out there as well....and it took a few years, and a combination of market/consumer pressure and new regs, and it's a rare automobile on the road these days that doesn't have air-bags...

Are we supposed to just "give up" and take whatever the manufacturers think we need, or can we (the ham consumers) actually ask/demand better?  
That is my MAIN point here...alternatives currently exist, and with similar or lower costs....so why not demand better and NOT settle?





"just fine"?
Well, that all depends on each and everyone's definition of "just fine", and of course on what radios you're talking about.... :)
Most radios will work just fine if the last ten % of power is not sent up the coax. Yes there are better radios for spectral purity but if you only running 100 watts into a dipole chances are you IMD is lost in the band noise floor.

Where spectral purity and adjacent channel frequency noise comes into play is when have a large beam up high with an amplifier. Now your 30-40 dB stronger and all the dirty laundry is out for all to see.
But, you do have a point....it is the "Big Guns" that can do the whole ham community a great service and be the forerunners here...
They have the money to spend on new radios with better transmit specs, so why don't THEY lead the way?  It will work out as a win-win for everyone!! (heck, how many "Big Guns" don't like having their egos stroked?)





Here we are in agreement....nobody here wants ham radio to become a "nanny state"!!!
This is amateur radio and where do you draw the line between experimentation and nanny state overreach to a perceived issue.
But, why can't we take pride in producing the best signal we can?   And, why can't we ask/demand better from the guys who gladly take or $$$..?





I have a call....and have been proud of it for 35 years....and I try to operate every day (although I DO have other things that take precedence)...
I wonder how many hams who worry about IMD so much, actually spend any time on the air. I figure if they don't have a call we can eliminate a lot of postings.
You may choose to ignore some postings, and that's your choice....but, the facts presented here will not change whether you ignore them, accept them, or choose to come on-board and help your fellow hams and the amateur radio service in whole...
(if you don't have the time/energy/inclination to actually contribute positively, that's fine.....I, myself, have many other commitments too, but at least try not to pour water on others attempts to make positive contributions and/or educate others....being negative / contrary, just seems a bit "un-ham-like", to me... :)




Nothing personal....and all in good cheer!!
Fair winds and sunny skies!



73,

John,  KA4WJA
 


Title: RE: Ham Xcvrs' and Amps', Transmit Spectral Purity, IMD Products, vs. comm/maritime
Post by: K2GWK on May 29, 2014, 06:02:32 AM
John,

The reason why I think it would have be easier to pressure the FCC to change (possibly through the ARRL) the spec and force the manufacturers to respond is that I think it will be very difficult to get the average Ham to give up the gear he has and purchase something new especially in light of the aging of our ranks. You may see results but it will take a long time to develop if ever. If the FCC were to change the spec you would see the manufacturers respond overnight. The other side of the coin is that if forced by the FCC the new design or approach for low IMD would be a matter of survival. If pressured by us, the radio operator, I bet the manufacturers would take advantage of the situation and spin it as Low IMD being a new feature of the transceiver and charge more money for it.


Title: RE: Ham Xcvrs' and Amps', Transmit Spectral Purity, IMD Products, vs. comm/maritime
Post by: KA4WJA on May 29, 2014, 06:10:59 AM
Guy,
I understand your point, and I do agree that FCC action would force the manufacturers to make the changes.

My "problem" is that in the long-term I really don't think more gov't regulation does anyone any good....(although I'm certainly no anarchist, it's just my personal philosophy here, so I fully accept others' opinions differ)


Thanks for sharing your thoughts.
Now, have 'ya got any "pull" with the ARRL and/or FCC?  :)


73,

John,  KA4WJA


Title: RE: Ham Xcvrs' and Amps', Transmit Spectral Purity, IMD Products, vs. comm/maritime
Post by: ZENKI on May 29, 2014, 06:47:55 AM
Government regulations did not bring about better receiver improvements for hams. Hams who discussed this is issue in a sensible manner brought about change.
Lets hope the same robust debate will wake the manufacturers from their design lazyboy positions and fix transmitter spectral purity. Name and shame  works effectively.
All the naysayers in ham community are all enjoying better equipment today because of a small minority of hams who raised the lack of  receiver performance issues in the ham community.

Already we  have  transceiver manufacturers  moving towards pre-distortion  technology in transmitters. At the same time some new manufacturers are improving transmitter IMD
performance. An example is the Zeus ZS1 transceiver. Even though its only a 15 watt transmitter its IMD performance is ahead of radios costing 10 times as much. This is progress.

http://www.remeeus.eu/hamradio/pa1hr/productreview.htm

I can only  imagine how  you would feel owning one of those   8000 dollar and above radios with such poor TX IMD performance. This even before
start talking about the  other transmitter issues that are not even mentioned. Sad really that only 1 or 2 radios on this list could even be considered acceptable.

In the commercial and military  HF industry the IMD performance of transmitters are  improving for the technical requirements of digital transmission.
An example is the Codan Envoy transceiver from Codan. 12 volt operation with -40Db per 3rd  IMD figures of -40db PEP for 125 watts of output.
You can clearly see why ham radio manufacturers are really many decades behind in their design expertise.

http://www.codanradio.com/product/envoy/

Hams who continue to have  have their heads buried in the sand against being proactive about improving standards are really just being argumentative for no good reason.
The reason for improving TX IMD is long term good  on many fronts even if these hams dont  really fully understand the debate fully. 








Guy,
I understand your point, and I do agree that FCC action would force the manufacturers to make the changes.

My "problem" is that in the long-term I really don't think more gov't regulation does anyone any good....(although I'm certainly no anarchist, it's just my personal philosophy here, so I fully accept others' opinions differ)


Thanks for sharing your thoughts.
Now, have 'ya got any "pull" with the ARRL and/or FCC?  :)


73,

John,  KA4WJA



Title: RE: Ham Xcvrs' and Amps', Transmit Spectral Purity, IMD Products, vs. comm/maritime
Post by: K2GWK on May 29, 2014, 06:55:36 AM
Guy,
I understand your point, and I do agree that FCC action would force the manufacturers to make the changes.

My "problem" is that in the long-term I really don't think more gov't regulation does anyone any good....(although I'm certainly no anarchist, it's just my personal philosophy here, so I fully accept others' opinions differ)


Thanks for sharing your thoughts.
Now, have 'ya got any "pull" with the ARRL and/or FCC?  :)


73,

John,  KA4WJA


I agree that we certainly do not need the government heaping any more regulations on us. IMHO government is much bigger than it needs to be. The fact is that the specification exists. I see no harm in changing an existing spec for the better. Heck, it would be nice for once having the government stick their nose in something and it do some good.  ;D


Title: RE: Ham Xcvrs' and Amps', Transmit Spectral Purity, IMD Products, vs. comm/maritime
Post by: K2GWK on May 29, 2014, 07:03:44 AM
Government regulations did not bring about better receiver improvements for hams. Hams who discussed this is issue in a sensible manner brought about change.
Lets hope the same robust debate will wake the manufacturers from their design lazyboy positions and fix transmitter spectral purity. Name and shame  works effectively.
All the naysayers in ham community are all enjoying better equipment today because of a small minority of hams who raised the lack of  receiver performance issues in the ham community.

Already we  have  transceiver manufacturers  moving towards pre-distortion  technology in transmitters. At the same time some new manufacturers are improving transmitter IMD
performance. An example is the Zeus ZS1 transceiver. Even though its only a 15 watt transmitter its IMD performance is ahead of radios costing 10 times as much. This is progress.

http://www.remeeus.eu/hamradio/pa1hr/productreview.htm

I can only  imagine how  you would feel owning one of those   8000 dollar and above radios with such poor TX IMD performance. This even before
start talking about the  other transmitter issues that are not even mentioned. Sad really that only 1 or 2 radios on this list could even be considered acceptable.

In the commercial and military  HF industry the IMD performance of transmitters are  improving for the technical requirements of digital transmission.
An example is the Codan Envoy transceiver from Codan. 12 volt operation with -40Db per 3rd  IMD figures of -40db PEP for 125 watts of output.
You can clearly see why ham radio manufacturers are really many decades behind in their design expertise.

http://www.codanradio.com/product/envoy/

Hams who continue to have  have their heads buried in the sand against being proactive about improving standards are really just being argumentative for no good reason.
The reason for improving TX IMD is long term good  on many fronts even if these hams dont  really fully understand the debate fully.

Zenki,

Therein lies the problem. I would bet that most Hams do not share your view and are happy with the status quo. As long a this is the case it will be very difficult to change things from this end. The truth of the matter is that as long as there is no incentive for the manufacturers to change, they won't. Getting the FCC to change the requirement will take care of that immediately. Otherwise what motivation is there for the manufacturers to change.



Title: RE: Ham Xcvrs' and Amps', Transmit Spectral Purity, IMD Products, vs. comm/maritime
Post by: W1BR on May 29, 2014, 07:07:59 AM
It looks like Palstar is making some effort to market a transmitter with decent IMD specs. The new TR-30 uses a 50-volt FET in the PA and the specs are pretty decent.  Not exactly a power house, but it is a start.


The TR30 has one of the industry's best transmit IMD performance, provided by a 50 Volt RF LDMOS FET transmitter final. 20 watt PEP output with IM3 of -48 dB PEP or -42 dBc is 10 to 20 dB better than today's popular transceivers. The TR30 is an ideal exicter for high-performance Linear RF Power Amplifiers that can provide 100 Watts PEP.


Title: RE: Ham Xcvrs' and Amps', Transmit Spectral Purity, IMD Products, vs. comm/maritime
Post by: AF6WL on May 29, 2014, 08:22:37 AM
It looks like Palstar is making some effort to market a transmitter with decent IMD specs. The new TR-30 uses a 50-volt FET in the PA and the specs are pretty decent.  Not exactly a power house, but it is a start.


The TR30 has one of the industry's best transmit IMD performance, provided by a 50 Volt RF LDMOS FET transmitter final. 20 watt PEP output with IM3 of -48 dB PEP or -42 dBc is 10 to 20 dB better than today's popular transceivers. The TR30 is an ideal exicter for high-performance Linear RF Power Amplifiers that can provide 100 Watts PEP.


But wouldn't  backing off a -30 dBc @ 100W PA by 6dB to 25W also yield -42 dBc IMD performance  ?


Title: RE: Ham Xcvrs' and Amps', Transmit Spectral Purity, IMD Products, vs. comm/maritime
Post by: KH6AQ on May 29, 2014, 08:29:40 AM
Getting the FCC to add a marine-transceiver like IMD requirement to amateur gear would work. I think that gear already in production would be grandfathered in. Clean transmitter IMD would run up against the IMD of many amplifiers. They too would need to be included in the new rules. There would not be an immediate improvement and significant on-the-air results could take a decade or more.

Who here has gone out of their way and paid more for a transceiver having marine grade IMD performance?

How much are we willing to pay for good IMD performance? It would raise the price of transceivers and amplifiers. Would $100 more for a transceiver or $1000 for an amplifier bother us?

The ICOM-M802 appears to achieve good IMD performance by using big and more expensive transistors. It's brute force and doing it at 11.5 volts with no 50 volt rail and no predistortion. Using the 1:4 manufacturing mark up rule a $25 increase in the PA cost raises the selling price by $100.


Title: RE: Ham Xcvrs' and Amps', Transmit Spectral Purity, IMD Products, vs. comm/maritime
Post by: W1BR on May 29, 2014, 08:35:08 AM
It may or may not... many amps have sweet spots where the IMD performance is best.  Third order IMD imay look good, while the odd order distortion products for the 5th, 7th, etc. that may go on forever.  That is the biggest problem with the RMI amps. You can reduce the drive and get decent (comparable to many rigs being sold) specs for the third order IMD products, but the other odd order products continue and wreck havoc for 10's of kHz. W8JI shows the results of IMD tests he ran on a RMI 300 watt PEP amp on his webpages. Most rigs and amps are analyzed using static two tone tests, while three tone tests can yield much more informative dynamic IMD analysis.

FCC regulations sound good on the surface, but they don't address hams who use ALC for aggressive speech processing, excessive mike levels, or simply over driving amps for some extra "PEP" on a wattmeter.  You would have to educate hams on proper transmitter operation; and the current licensing system is lacking in that regard.

Pete


Title: RE: Ham Xcvrs' and Amps', Transmit Spectral Purity, IMD Products, vs. comm/maritime
Post by: KH6AQ on May 29, 2014, 10:06:27 AM
Good point on operator error. Operator error can be overcome by designing transceivers to always be clean.



Title: RE: Ham Xcvrs' and Amps', Transmit Spectral Purity, IMD Products, vs. comm/maritime
Post by: DL8OV on May 29, 2014, 10:19:20 AM
I have a suggestion (and I hope that someone from Icom is reading this thread). As the Icom 7800 is modular why not bring out a new version IC-7800M where the electronics and firmware are to marine specification, charge a little extra and then see if the rig is taken up?

Also there is one thing that maybe nobody has noticed, marine transceivers do not have a microphone gain control. I'm sure that this explains some of the better IMD figures.

Peter DL8OV


Title: RE: Ham Xcvrs' and Amps', Transmit Spectral Purity, IMD Products, vs. comm/maritime
Post by: KA4WJA on May 29, 2014, 02:48:51 PM
Okay, thanks to the suggestions here, I've looked at the Apache Labs ANON-100D, and the Flex products...
And, I think there is some good news here!!
(although, I do wonder if the SDR's will ever replace the "knob" radios in the main stream?)


I found the Apache site to be a great source of info, and their ANON-100D does look great!!
It is a bit pricey, at $3500 (plus accessories to make it complete?), so it's definitely marketed at the high end of the market...but, if the transmit spectral purity is as good as their 3rd order specs, this may well be a very nice addition to our airwaves!!



As for Flex (I have to get over my experience hearing a few Flex-1500's on the air, 'cause they really were quite awful)...but, I went to their site and found nothing about transmit spectral purity, nor transmit IMD....(and yes, I downloaded the data sheets)...
And, with the Flex-6500 at $4300, it's even pricier that the ANON....


And, the "SSB Electronics Zeus ZS1" just seems like a QRP SDR....and at ~ $2000 (plus accessories), it might appeal to a wider section of the ham population, but I'm not sure this will ever be a "main stream"



But, I still think that until we get the main stream manufacturers on-board, the small number of high-end SDR users won't have too much effect...
And, when you add in some "operator preferences" for wide transmit audio (and hi-fi SSB), we may have clean transmitters that hams are adjusting / setting to take up a bit more "space" on-air??  (not sure if this is real concern, or just my paranoia :)



I haven't been able to find anything about the Kenwood TS-990 being "upgraded" to use "pre-distortion" or otherwise improve its transmit spectral purity / transmit IMD...
And, although it isn't the worst on the market...it's an $8000 radio and its transmitter is below average?
Perhaps there is info that is not on their site?



Ken,
I'm afraid I'm not up-to-date with what future developments Flex and ANON might be working on....(thanks for the heads-up, I'll look into it...)

But, the point I'm trying to make is, there ARE currently full-featured, HF transceivers, that provide excellent service on the ham radio bands, that have excellent transmit spectral purity and extremely low IMD products, with the IMD products that actually cause most of the splatter (5th and higher order products), completely non-existent....
And, these radios are now currently on the market (and have been for years), at a reasonably "affordable" price...(< $2000)
The manufacturers are already making these radios and selling them for $1000 - $1800 retail....nobody needs to wait until some software engineer works out kinks in some $10,000 radio...
 



Maybe you guys can pass on some more details on some of these "coming soon" features/specs, etc. ?



Anyway, thanks again for the heads-up about the ANON-100D!


73,

John,  KA4WJA



Title: RE: Ham Xcvrs' and Amps', Transmit Spectral Purity, IMD Products, vs. comm/maritime
Post by: KA4WJA on May 29, 2014, 03:30:33 PM
Peter,
I like your thinking!!
I have a suggestion (and I hope that someone from Icom is reading this thread). As the Icom 7800 is modular why not bring out a new version IC-7800M where the electronics and firmware are to marine specification, charge a little extra and then see if the rig is taken up?

Also there is one thing that maybe nobody has noticed, marine transceivers do not have a microphone gain control. I'm sure that this explains some of the better IMD figures.

Peter DL8OV


And, you are quite correct....no mic gain, no knobs to "turn all the way up"!!


73,

John,  KA4WJA


Title: RE: Ham Xcvrs' and Amps', Transmit Spectral Purity, IMD Products, vs. comm/maritime
Post by: K2GWK on May 30, 2014, 04:48:18 AM
I have a suggestion (and I hope that someone from Icom is reading this thread). As the Icom 7800 is modular why not bring out a new version IC-7800M where the electronics and firmware are to marine specification, charge a little extra and then see if the rig is taken up?

Also there is one thing that maybe nobody has noticed, marine transceivers do not have a microphone gain control. I'm sure that this explains some of the better IMD figures.

Peter DL8OV

That is a great suggestion but the only problem is Icom will only develop the new modules if there is a market for them. The 7800 is a expensive radio as it is. How many more radios would they sell because of the new modules? My guess is not enough to justify the non-recurring engineering costs, new production and marketing costs.


Title: RE: Ham Xcvrs' and Amps', Transmit Spectral Purity, IMD Products, vs. comm/maritime
Post by: K6AER on May 30, 2014, 09:12:55 AM
The original IC-7800 was developed for the US Embassy contract for HF radios capable of computer frequency hopping control. When ICOM offered the radio to the ham market the style of operation is different and hams operate at very close frequency spacing. As a result the radios receive filters had to be upgraded to conform to the narrower bandwidth issues.

The IC-7800 is basically a Mil Spec commercial radio. Even at $10,000 the bandwidth of the IC-7800 transmission is mostly controlled by the mic. gain knob.

Radio IMD is partial to the amplifier design but is also a result of Oscillator LO phase Noise and RF chain linearity.  Phase noise offers an unlimited mix of frequencies and contributes to the transmitted noise floor in the primary signal. As you have seen in other posts, the  transmitter must have a transmitted signal signature to fit within the boundaries assigned by the FCC spectral mask. The first big step in improving transmitter spectral mask is to reduce the LO phase noise. This is no easy task.

ICOM will not develop any new modules for the IC-7800. The radio design is 10 years old and nearing it marketing life. How many hams are going to spend another $10,000 for a newer radio with 15 dB better performance on Spectral width and LO noise floor improvements? Very few.

So far the best radio I have seen is the Flex 6500 series at -145 dBc phase noise at 10 KHz. The Hilberling PT-8000A is -142 dBc at 10 KHz. That said, 99% of hams are happy just to make a contact and could care less about the spectral mask.

Another problem with this quest for the best IMD is the FCC does not care a whit about our spectral signal width. Ham radio is for experimenting. Just as long as we fallow basic rules and don’t interfere with outside services we are free to play nice in the sand box.


Title: RE: Ham Xcvrs' and Amps', Transmit Spectral Purity, IMD Products, vs. comm/maritime
Post by: KA4WJA on May 30, 2014, 11:25:52 AM
Mike,
Thank you for contributing such helpful information!!
I appreciate it and I suspect that many others here do as well!



---  Mike, here we are in full agreement!! (and, I like your wording about "playing in our sandbox"....how true this is!!!)
Another problem with this quest for the best IMD is the FCC does not care a whit about our spectral signal width. Ham radio is for experimenting. Just as long as we fallow basic rules and don’t interfere with outside services we are free to play nice in the sand box.
I am not one to stifle experimenting...far from it actually....and I'd like it if more hams knew more about the radios, radiowave propagation, antenna radiation, etc. etc..
And these facts, that the FCC leaves us to our own devices, also further shows how if we hams do want changes, it is actually up to us....

As I have been saying, we hams have the power ($$$$) to ask/demand the manufacturers make/sell what we want...
If we accept crap, we get more crap.....that's the market!!
If we no longer accept it at all...and we make our intents and desires known....sooner or later, things will change...

Will some manufactures go out-of-business or simply leave the amateur radio market....yes, that will probably happen....but newer players will come and take their place...
Will Apache Labs or some other upstart become the "Yea Com Wood" of the next decade?
I don't know....
But, I do know that IS up to us, to ask/demand change (if that is what we hams want)...
If we do nothing, we get what we deserve....nothing!!





--- While I do like Peter's idea (put some of the IC-7800 user interface together with the M-802's guts), I think we all know it's a pipe dream that ain't gonna' happen... :)  :)
As you write (and as I showed earlier) there is a LOT more to this than some "3rd order numbers"!!
And, of course designing a radio, soup-to-nuts, w/ low-phase noise osc., extremely linear circuits, etc. isn't child's play....(which is why I defer to those of you that do it for a living!)



--- Meeting the spectral purity masks might not be easy, but it IS being done (and has been done for many years), by the same factories that make our ham gear....and these radios do NOT cost $10,000...
(and before you go and think the marine HF market is bigger than the ham radio market....sorry, but Icom's marine HF market is almost completely the small niche of offshore pleasure boats, sail or power....the commercial fishing, large merchant vessels, etc. are served by the likes of Furuno, Thrane & Thrane/Sailor/Skanti, etc...so, in reality Icom's ham HF radio market / consumer base is many times larger than their maritime HF market...)

Now of course, these marine HF rigs are not as feature-packed as many ham rigs, but you could buy a half-dozen Icom M-802's, for the price of one IC-7800....and the Yaesu/Vertex, Kenwood, etc. maritime and land mobile HF rigs are just as "inexpensive"....heck the $1200 Icom M-700Pro had one of the cleanest HF transmitters of any 150-watt "12vdc" PA radio ever....and I talk to folks using them all the time....never a hint of splatter, anywhere...

So, while I understand it "isn't easy", please also understand that it "isn't that expensive" either!!  Current production radios that meet /exceed those specs, and fit under the "mask",  are being sold right now, today, brand new-in-the-box, for $1800...
How many hams are going to spend another $10,000 for a newer radio with 15 dB better performance on Spectral width and LO noise floor improvements? Very few.
A radio that meets those specs (an Icom M-802) is just a few steps away from me right now...it is a current production model, and you can order one today for about $1800....
Now, that is NOT an "entry-level" price point, to be sure...
But, this is also NOT an ego-stroking, high-end, $10,000 radio...

I'm wondering why people are assuming that a radio that meets these specs, etc. would cost $10,000??  Because it just isn't so....




--- While the current production $1800 Icom M-802 doesn't have quite as good osc phase noise numbers as the $4500 Flex, nor the ? $15,000 - $20,000? PT-8000A....it IS actually better than the $10,000 IC-7800....and better than most HF ham rigs being sold...
So far the best radio I have seen is the Flex 6500 series at -145 dBc phase noise at 10 KHz. The Hilberling PT-8000A is -142 dBc at 10 KHz. That said, 99% of hams are happy just to make a contact and could care less about the spectral mask.
And, while I don't have the exact numbers for the older (1990's/2000's) $1250 Icom M-700Pro, looking at its very clean transmit spectral purity, I suspect that was as good as these other radios you site, costing many times as much...



Just some more of my ramblings.... :)



73,

John,  KA4WJA



{ P.S.   BTW, it's been my understanding that in SSB service, it is the higher order distortion products that fall well outside the operating passband/channel, that are the cause of the splatter that we comment/complain about..
So, while so many reviews / specs show 3rd numbers (and some show the higher order), for our typical SSB service, it is the higher order numbers that are of more concern...
(although as I wrote in my original post here, I'd prefer a dynamic approach using either white noise or voice, to better determine what we're comparing....the numbers that we have are the numbers that we have...so, we just need to use what we've got..) :) }


Title: RE: Ham Xcvrs' and Amps', Transmit Spectral Purity, IMD Products, vs. comm/maritime
Post by: KH6AQ on May 30, 2014, 11:39:48 AM
A plot of the IMD products can be seen in some QST reviews while some reviews list only the 3rd and 9th order numbers.

The IC-7800 review lists 3rd and 9th but doesn't show a plot. Perhaps the expanded review shows it.

http://www.icomamerica.com/en/products/amateur/hf/7800/IC7800_QSTReview.pdf

Does LO phase noise encroach on the marine spectral purity mask? For the IC-7800 the phase noise at 1 kHz is -105 dBC.




Title: RE: Ham Xcvrs' and Amps', Transmit Spectral Purity, IMD Products, vs. comm/maritime
Post by: KA5PIU on June 01, 2014, 01:54:40 PM
Spectrum purity is an issue with the CAP and the like.
Most ham rigs do not make the cut!
On the other side of the coin is the "Hacker mod" VX-3r.
Sure, it can transmit where it can receive, pretty much everywhere!
The problem is that it does the transmitting everywhere all at once!
In order to have the thing transmit at 30 MHz, all of the filtering was removed, so the second harmonic of 60 MHz is very present, 90 MHz, 120 MHz, etc.
It is not all that bad if the radio is running on battery, 1 watt.
But, 2 watts external power? NO!
This is the same problem with any wideband design.
The neat part about HF is that it IS harmonically related, 160 Meters, 80 Meters, 40 Meters 20 Meters, 10 meter.
As long as you stay in the related bands, and in the center, you will be fine, hopefully.
But, most hams want that last bit of power, and push things to the point of splatter.
I do not agree or disagree with the VX-3r mod, it is what it is.
But, from a good engineering practice standpoint, it is wrong.
We, as hams, should be setting good engineering practice standards, examples others can look up to.
A really clean signal should be an example.


Title: RE: Ham Xcvrs' and Amps', Transmit Spectral Purity, IMD Products, vs. comm/maritime
Post by: KA4WJA on June 10, 2014, 10:43:33 AM
Rudy,
This was my main point here....that it is up to us!!

We, as hams, should be setting good engineering practice standards, examples others can look up to.
A really clean signal should be an example.
Maybe we can all jump on this as our "dream"??  :)

73,

John,  KA4WJA


Title: RE: Ham Xcvrs' and Amps', Transmit Spectral Purity, IMD Products, vs. comm/maritime
Post by: K2GWK on June 10, 2014, 12:49:48 PM
Rudy,
This was my main point here....that it is up to us!!

We, as hams, should be setting good engineering practice standards, examples others can look up to.
A really clean signal should be an example.
Maybe we can all jump on this as our "dream"??  :)

73,

John,  KA4WJA


Alright, I'll bite. How do you propose we change things??


Title: RE: Ham Xcvrs' and Amps', Transmit Spectral Purity, IMD Products, vs. comm/maritime
Post by: G3RZP on June 10, 2014, 01:20:49 PM
For the RSGB Convention in 2014, I made a presentation entitled 'Clean Signals or Spreading the Sewage' (I wanted to call it 'Slinging the sh*t' but that wasn't acceptable!) For that, I analysed 132 transmitters/transceiver product reviews back to the 1970s, and what stood out was that with the exception of those Yaesu rigs which could run in Class A, the cleanest rigs in terms of high order IMD were the last generation of tube rigs. Regrettably, because my current ISP only allows 2MB of attachments, I can't send the presentation.

But let us stop and think. Just assume that the adjacent channel energy in an SSB bandwidth - including phase and wideband amplitude noise - is -60dB rel PEP, or of the order of -94dBc/Hz. For the transmitter to be the dominant factor, receiver adjacent channel rejection including phase noise must be at least 104dBc/Hz, averaged over a 3 kHz bandwidth, which could be a problem. In the marine world, yes they stack channels at 3 kHz BUT the coast stations are on separate frequencies to the ships. This means that for most situations, the separation between transmitting stations in terms of frequency is actually quite large....

So just how much do we REALLY need in practice in terms of transmitter cleanliness and receiver selectivity?


Title: RE: Ham Xcvrs' and Amps', Transmit Spectral Purity, IMD Products, vs. comm/maritime
Post by: KA4WJA on June 10, 2014, 04:28:44 PM
Guy,
How about these things, for a start?

Alright, I'll bite. How do you propose we change things??



I've got 5 things, right off the top-of-my-head....and all are things that I do, am doing, and will be doing...so, I'm not asking anyone to do anything that I'm not doing myself!!


1)  Put our money where our mouths are!  
a)  Buy only radios that meet tighter standards, and refuse to buy any radio that does not!

I have already put MY money where my mouth is...
I have refused to buy any new ham radio that does not meet significantly tighter specs, and I have bought radios that DO meet these specs.

I own TWO Icom M-802 HF transceivers, and use one of them regularly (almost daily) on the ham radio bands...

(http://www.c470.jerodisys.com/470pix/4700307f.jpg)
(http://www.c470.jerodisys.com/470pix/4714801f.jpg)



b)  Buy only amps that meet tighter specs (this typically means GG triode amps, and 3CX1500/8877, and/or 3CX1200, etc. in particular), and refuse to buy amps that do not...

I have already put MY money where my mouth is...
I have refused to buy any new amp that does not meet tighter specs, and I have bought amps that DO meet these specs.

I own an Alpha 77 and a Tempo 2002....(and I built/own an SB-221 about 35 years ago, that my best friend has been using for > 10 years)...

(http://files.qrz.com/a/ka4wja/Ham1.JPG)


And, tell every radio and amp manufacturer (by e-mail, snail-mail, and/or phone) of our decisions above, to NOT buy another radio or amp, until they produce units that meet these specs!
(If I have time, and remember, I'm starting this tomorrow!)




2)  Make better use of the radios that we have....
a)  If you can use 10% - 25% less power, use less power!!
This will make a difference (as Mike has mentioned), and especially when driving an amp, REDUCE your drive power, and do NOT try to squeeze every last watt out...driving any amp into compression is NOT good!!
(I do this with my Drake TR-7's, which come close to meeting the old Part 80 specs at rated 150watts out, but are even better at 100 - 120 watts out...)
But, understand that many radios operated at significantly lower power levels, such as 50% - 75% below rated output, can have worse transmit purity / worse IMD products...so, backing off a little is good, backing off a lot is usually not good...

b)  Turn DOWN your mic gain!!!

c)  If you have a rig with ALC (most do), use as little ALC as you can....most modern ham transceivers will have better transmit purity with no ALC measured or just a "tickle" of the ALC meter...

d)  Do not use speech processing unless necessary, and then only as much processing as needed...

e)  Do NOT use an amplified mic, nor should you "swallow your mic" and/or scream...




3)  Learn, and teach others, how to tune their amps!!!
(and as mentioned above, do NOT drive the amp into compression!!)



4)  Promote this "philosophy" / "plan", ON-THE-AIR, at club meetings / hamfests, on-line / on the internet, and maybe even give seminars explaining these things!!

This point....teaching other hams about all of this, is important!!
As, can be seen by just this discussion here, there are experienced hams, some have worked in engineering for years, that have mistakenly thought that radios that meet these tighter specs (such as the maritime Part 80 specs) would cost $10,000....
But, as many now know this is completely false....as radios that meet these specs and are used everyday on-the-air (ham, marine, and land mobile), cost between $1000 and $1800 (w/ IF-DSP, etc.)



5)  Be conscientious about standing our ground against those promoting "cheap 10 meter amps", etc. and do not give up!!




I hope these few things prove to be a good start...maybe others will have further ideas that will promote this old "philosophy" (has everyone forgotten that "good engineering" and "good amateur practice", actually BEING part of the purposes/rules of the Amateur Radio Service?   Maybe these old "philosophies" will become SOP once again?  We can all hope!!)


73,

John,  KA4WJA

  


Title: RE: Ham Xcvrs' and Amps', Transmit Spectral Purity, IMD Products, vs. comm/maritime
Post by: KA4WJA on June 10, 2014, 04:54:32 PM
Peter,
This sounds like a great way of promoting a "clean signal philosophy"!!
Maybe you can figure out how to do this "Clean Signals or Spreading the Sewage" presentation at Dayton some year, or maybe even post it on Youtube?
 I'd love to see it!!

I have some Youtube videos, mostly just Icom M-802 instruction videos and videos showing some layperson explanations of choosing the correct frequencies / radio propagation, etc..

Here's my Youtube channel..
http://www.youtube.com/user/captainjohn49/videos


Here is one video showing the M-802 "VFO mode"...
 http://www.youtube.com/watch?v=Do93zYE20OM
 
Here is my favorite, showing HF-DSC signaling (100-baud FSK)...
 http://www.youtube.com/watch?v=LgnBiGNbWNU

And, another showing a laypersons explanation of choosing the appropriate frequency...
 http://www.youtube.com/watch?v=T-1LgNioO6w

And, another showing the rather rare use of a coast station (placing a radio-telephone call)...
 http://www.youtube.com/watch?v=bT2Wz3uVWB8



For the RSGB Convention in 2014, I made a presentation entitled 'Clean Signals or Spreading the Sewage' (I wanted to call it 'Slinging the sh*t' but that wasn't acceptable!) For that, I analysed 132 transmitters/transceiver product reviews back to the 1970s, and what stood out was that with the exception of those Yaesu rigs which could run in Class A, the cleanest rigs in terms of high order IMD were the last generation of tube rigs. Regrettably, because my current ISP only allows 2MB of attachments, I can't send the presentation.

But let us stop and think. Just assume that the adjacent channel energy in an SSB bandwidth - including phase and wideband amplitude noise - is -60dB rel PEP, or of the order of -94dBc/Hz. For the transmitter to be the dominant factor, receiver adjacent channel rejection including phase noise must be at least 104dBc/Hz, averaged over a 3 kHz bandwidth, which could be a problem. In the marine world, yes they stack channels at 3 kHz BUT the coast stations are on separate frequencies to the ships. This means that for most situations, the separation between transmitting stations in terms of frequency is actually quite large....

So just how much do we REALLY need in practice in terms of transmitter cleanliness and receiver selectivity?

BTW, while when working with commercial coast stations (which, except for WLO/KLB's customers, is actually VERY rare these days), the duplex channels used do have sufficient spacing (as these old coast stations were also designed with physical separation between the receive and transmit sites, as they were/are used for full-duplex radio-telephone interconnects)....the actual facts regarding daily operations on the maritime bands, are that stations ARE using ADJACENT channels, with no "guard bands" or room to spread out...(particularly on the two most used bands...8mhz and 12mhz maritime ship-to-ship and ship-to-shore-simplex comms ARE using adjacent channels, because there are few channels available....)
Sorry to say, but there is meaning to the rules....


And, just my opinion here, but I actually believe that we hams DO need better transmit cleanliness!!
Typically our receivers cannot work up to their potential do to the crappy transmitters that many use...
I don't buy the premise that "we don't need anything cleaner"!!



Please understand that I mean nothing personal here at all!!!
Against anyone at all!!
But, in my opinion, those that tout that we don't need cleaner transmitters, are just my fellow hams justifying some things, like their unwillingness to admit their radio isn't so great after all, and/or some ignorance of how things work, and how things can work much better for not a lot of money...
Again, nothing personal to anyone here...just my ramblings... :)  


73,

John,  KA4WJA


Title: RE: Ham Xcvrs' and Amps', Transmit Spectral Purity, IMD Products, vs. comm/maritime
Post by: WB2WIK on June 10, 2014, 05:59:22 PM
Clean signal philosophy is great, but hams will be hams and often try to squeeze out the last microbel out of stuff.

And then there are those who like "high fidelity" SSB and use external gear the transmitter equipment manufacturer never recommended or even knew about to boost modulation frequencies for that "special sound."  Modulating many SSB rigs at frequencies below 300 Hz results in all kinds of unwanted byproducts the manufacturer didn't design for.

It's only a hobby. ;)

If I get tired of all the crap, I go back to CW where I rarely have to deal with key clicks nowadays.


Title: RE: Ham Xcvrs' and Amps', Transmit Spectral Purity, IMD Products, vs. comm/maritime
Post by: AA4PB on June 10, 2014, 06:51:33 PM
If I get tired of all the crap, I go back to CW where I rarely have to deal with key clicks nowadays.

Just wait until sound card CW becomes more pervasive.  :o


Title: RE: Ham Xcvrs' and Amps', Transmit Spectral Purity, IMD Products, vs. comm/maritime
Post by: WB2WIK on June 10, 2014, 06:58:42 PM
If I get tired of all the crap, I go back to CW where I rarely have to deal with key clicks nowadays.

Just wait until sound card CW becomes more pervasive.  :o


I can always tell when someone is using one.  And they do regularly clutter up the bands with artifacts not found from direct keying a CW rig.


Title: RE: Ham Xcvrs' and Amps', Transmit Spectral Purity, IMD Products, vs. comm/maritime
Post by: K2GWK on June 11, 2014, 09:31:30 AM
Yeah, asking Hams not to buy a new rig because it passes the FCC IMD spec but is not a clean as some would like it....... That will happen...Not!!


Title: RE: Ham Xcvrs' and Amps', Transmit Spectral Purity, IMD Products, vs. comm/maritime
Post by: KA4WJA on June 11, 2014, 11:39:08 AM
This (and a few other posts here) does bring up questions that I have...
Yeah, asking Hams not to buy a new rig because it passes the FCC IMD spec but is not a clean as some would like it....... That will happen...Not!!
I suppose it is highly possible that most here think these ideas have merit, but little chance of success, and are just trying to make sure that we all comprehend the "realistic view" that quite possibly nothing will happen, no matter what is written here, nor what effort I, and a few others, undertake?
But, I just don't quite get the veiled negativism?


I wrote that I understood this was a long uphill battle, and that I had no false assumptions that it would be easy at all...
And, I understand that it IS asking a lot of us cheap hams... :)

When I was asked directly what I purpose we do to change things, I promptly responded with 5 things that I'm doing (and hope some others will do as well)...and still, what gets posted are pessimistic thoughts, about how cheap we hams are (yes, I know that, and stated that right up front), etc....

So, while I originally thought that many were just posting thoughts of concern over having high expectations...it's starting to look like no one is actually happy that someone cares / someone is willing to do something?
I'm just scratching my head, wondering if this is true, and if so, why?


So again, yes we ALL know that hams are cheap....we ALL know that many are ignorant of the facts....we ALL know that without FCC specs, it is unlikely that the manufacturers will make significant changes, etc. etc. etc...
(and, I have stated all these things myself, up front)
I'm just wondering why so many here seem to have little of a positive nature to contribute?


Since we now have dozens of negative comments on my ideas/goals, maybe we could try a different approach....
I'm thinking that I should have started this whole thread with these questions first!

1)  Is there anyone here who actually thinks having ham transceivers with better spectral purity would be a good idea, and are interested in contributing positively to the effort?

2)  Is there anyone here who thinks some of my ideas/thoughts have merit, but don't think they have a realistic chance of success (but may wish us well)?

3)  Is there anyone here who thinks poor transmitter purity is "just fine", and thinks this whole issue is a waste of their time to even learn about?


So, anyone care to bite and answer.... :)
Place yourself firmly on-the-record, one-way or the-other....no fence sitting allowed now....
Choose your category....#1,  #2,  or #3.... :)
(be advised though, that if you choose #1 or #2, negative comments would be contrary, and look kinda' bad.. :)




73,

John,  KA4WJA


Title: RE: Ham Xcvrs' and Amps', Transmit Spectral Purity, IMD Products, vs. comm/maritime
Post by: DL8OV on June 11, 2014, 01:35:17 PM
It looks like I am the first:

1)  Is there anyone here who actually thinks having ham transceivers with better spectral purity would be a good idea, and are interested in contributing positively to the effort? Yes, I am.

2)  Is there anyone here who thinks some of my ideas/thoughts have merit, but don't think they have a realistic chance of success (but may wish us well)? This is unfortunately more like reality but I wish it was not the case

3)  Is there anyone here who thinks poor transmitter purity is "just fine", and thinks this whole issue is a waste of their time to even learn about? Either I have a good signal or I do not operate, it is a simple choice. We do not accept an automobile that drives down the road emitting clouds of blue smoke so why accept a transceiver that emits a poor signal?

Peter DL8OV


Title: RE: Ham Xcvrs' and Amps', Transmit Spectral Purity, IMD Products, vs. comm/maritime
Post by: G3RZP on June 11, 2014, 01:45:33 PM
Now let's look at this

>1)  Is there anyone here who actually thinks having ham transceivers with better spectral purity would be a good idea, and are interested in contributing positively to the effort?<

This leads to the questions;-

1. How much better?

2. Why? i.e. justify the better figures. This means looking at the levels of received signals on average - worst case isn't acceptable, it needs the average plus/minus three standard deviations and deciding how fare  down the splatter needs to be to be 10dB below the weakest signals that fall within the envelope of received signals.

Now that means that a number of signals will still cause splatter, but you cannot write regulations to control the few without being far too severe upon the many.

There becomes a practical level of high order IMD which it is both unnecessary and too expensive to exceed. Personally, I believe the current levels of IMD from transceivers on the market are excessive, coupled with the fact that a lot of it is high order. But there is the economic case - if specs are too tight and equipment is thus too expensive or not available, is that desirable too?

Yet it does not alter the fact today that rigs with a 12BY7 driving two or three 6146Bs are cleaner than the equivalent power output SS rigs...but the mathematics of transfer characteristics and Fourier suggest that anyway.


Title: RE: Ham Xcvrs' and Amps', Transmit Spectral Purity, IMD Products, vs. comm/maritime
Post by: K2GWK on June 12, 2014, 06:49:44 AM
I suppose it is highly possible that most here think these ideas have merit, but little chance of success, and are just trying to make sure that we all comprehend the "realistic view" that quite possibly nothing will happen, no matter what is written here, nor what effort I, and a few others, undertake?
But, I just don't quite get the veiled negativism?

John,

I don't think you have had many, if any responders to this thread that disagree with you. I think your approach to changing things is a little "pie in the sky" though. Being realistic, it will be next to impossible to convince most Hams when it is time for their next rig to buy a Marine HF radio or an old tube radio because it has better IMD  performance. This is especially true when the radios out there that do not perform as well with respect to IMD actually are within the FCC's specification. I am not sure that most Hams understand the ramifications  of poor IMD. My point is that if you are serious about changing things in our lifetime, it would far easier to convince the FCC to tighten the spec than to convince enough Hams to refrain from purchasing rigs that are barely better than the existing spec to put pressure on the manufacturers to change. I am not being negative, I am being realistic.


Title: RE: Ham Xcvrs' and Amps', Transmit Spectral Purity, IMD Products, vs. comm/maritime
Post by: KA5PIU on June 12, 2014, 07:26:17 AM
Hello.

I get on 160 with an old Marine AM radio, commercial unit, and it is super clean!
It does 1.8 to 2 MHz with NO problems, other than retuning, there was nothing done to it, 90 watts.
I do 10 meters with an old German police radio, AM or FM.
I do VHF with old commercial gear, have a complete Motorola low band and high band and UHF vehicular repeater system.
Purity of signal is one of my hallmarks.
Now, some stuff I build, and for the most part, I stick with CW, AM or FM.
It is just easier to get a clean signal out with the 3 modes.
SSB requires a lot of work, a lot of filtering, to get right.
So, I do not homebrew SSB.
Enjoy!


Title: RE: Ham Xcvrs' and Amps', Transmit Spectral Purity, IMD Products, vs. comm/maritime
Post by: KA4WJA on June 19, 2014, 01:37:34 PM
Guy,
Sorry about not responding earlier, I just saw this post...
John,

I don't think you have had many, if any responders to this thread that disagree with you. I think your approach to changing things is a little "pie in the sky" though. Being realistic, it will be next to impossible to convince most Hams when it is time for their next rig to buy a Marine HF radio or an old tube radio because it has better IMD  performance. This is especially true when the radios out there that do not perform as well with respect to IMD actually are within the FCC's specification. I am not sure that most Hams understand the ramifications  of poor IMD. My point is that if you are serious about changing things in our lifetime, it would far easier to convince the FCC to tighten the spec than to convince enough Hams to refrain from purchasing rigs that are barely better than the existing spec to put pressure on the manufacturers to change. I am not being negative, I am being realistic.

I'm afraid you are correct that no ham (or darn few anyway) is going to buy a $1800 marine radio, just because it has a cleaner transmitter, when time comes to buy a new radio...

And, while it is still realistically "pie-in-the-sky", what would happen if nobody (or darn few) actually bought new HF rigs for one year, with the "boycott" due to inferior transmit spectral purity?
[Yes, I DO realize that isn't going to happen!]
But, if a revolution gets started where more hams vote with their wallets, and refuse to buy radios with crappy transmitters, maybe, just maybe some manufacturers would take notice and start making better transmitter?

Yeah, I can see your eyes rolling....and I imagine you're all thinking what has that guy been smoking? :)
No worries, we can all dream, right??



But in all seriousness, my original point of this thread was:
a)  to point out that modern IF-DSP, HF rigs, with exceptional transmit IMD specs, and excellent transmit purity are being sold right now...made by the same manufacturers that are advertising constantly and displaying their wares at Dayton, etc.
b)  they are not more expensive than the typical ham HF transceiver, selling for about $1000 - $1800...
c)  they ARE using 12vdc PA's....
d)  hopefully give some of my fellow hams a pause, to consider what they are buying / using on the air....i.e. what their transmit signal is actually like, and how it could be better!!

So, if I accomplished these few things, I think this thread succeeded.....
And, if we can actually get some people to call/write/e-mail some of these manufacturers, well that would be great icing on the cake... :)




Guy, I'd like to personally thank you for your intelligent comments and contribution here!


73,
John,  KA4WJA
 


Title: RE: Ham Xcvrs' and Amps', Transmit Spectral Purity, IMD Products, vs. comm/maritime
Post by: ZL1BBW on June 19, 2014, 01:59:09 PM
Guess I will have to stick with my old transceiver with TX 3rd order Intermod better than minus 40db.


Title: RE: Ham Xcvrs' and Amps', Transmit Spectral Purity, IMD Products, vs. comm/maritime
Post by: KA5PIU on June 19, 2014, 04:06:07 PM
Hello.

Some are missing the point.
I am cheap, and buy cheap!
But, even with that said, I have no trouble in finding cheap used marine radios, none whatsoever!
The point being, quality need not be expensive.
They narrow banded a while back, and crates of used cop radios are out there, cheap!
So, MF/HF/VHF/UHF, all excellent quality! all cheap!
Sure, you do not get a brand new in the package new radio with all the latest features.
But you get a radio that just works, and works better!
Hams CAN improve!


Title: RE: Ham Xcvrs' and Amps', Transmit Spectral Purity, IMD Products, vs. comm/maritime
Post by: K5PB on July 23, 2014, 09:35:13 PM
I’m a bit late arriving at this discussion, but it is on a subject that I have long considered important and also very much neglected, especially in recent years.  But first, many thanks John KA4WJA , not only for bringing it up but for a highly lucid and logical presentation.  Not having looked at the specs on marine transceivers for a long time, I was surprised at how much better they can be, even with 12V on the finals.

The poor transmit IMD performance of most recent hamband transceivers, even the expensive ones, of around 27 or 28 dB 3rd order is a travesty.  It’s one of the reasons I have not bought one and have held onto my trusty old TS-830S.  That old radio is at least 8-10 dB better on 3rd order IMD than most modern SS transceivers, and probably even better on the higher order stuff.

It may be true that many hams are not familiar with the technical aspects of IMD, but they all certainly understand the practical effects of QRM and splatter.  A  widespread transmit IMD improvement of 10 dB on our crowded HF phone bands would work wonders and make operating much more pleasant for all.  More to the point, it’s attainable.

For those who are reluctant for the FCC to step in, perhaps they should be reminded that the FCC is already involved.  It’s only a matter of tightening up the existing numbers.  To make it easier for manufacturers to comply  with more stringent IMD standards, and to lessen the financial impact, the FCC could easily set a compliance date at some reasonable point in the future.

I believe that ARRL should petition the FCC to take such action on behalf of all amateurs.  Letters to our respective Division Directors would help to get the ball rolling.  As a result of widespread amateur interest, a great deal of progress has been made in strong-signal receiver performance.  But that is only half of the equation.  We need now to turn our attention to the transmit side.

Best wishes to all,
Stu, K5PB
Collins Radio, Retired



Title: RE: Ham Xcvrs' and Amps', Transmit Spectral Purity, IMD Products, vs. comm/maritime
Post by: G3RZP on July 23, 2014, 11:16:00 PM
Unfortunately, we can't post pictures, as I have some slides of marine specs and typical ham rig spectral purity that I used for my lecture 'Spreading the sewage' at last year's RSGB Convention, looking at this whole problem.


Title: RE: Ham Xcvrs' and Amps', Transmit Spectral Purity, IMD Products, vs. comm/maritime
Post by: K5PB on July 24, 2014, 02:43:20 PM
Regarding transmit IMD standards, here is the case for needed FCC action to raise them.  In this price-competitive market, it is extremely doubtful that any amateur transceiver manufacturer would be willing to take such action on its own.  Manufacturers want and need a level playing field, with standards that apply to all.  This is entirely understandable and reasonable.  But as modern HF marine transceivers have demonstrated, significant progress is attainable, most likely without major redesign.

The situation is similar to the automobile business regarding Corporate Average Fuel Economy (CAFÉ) standards set by the federal government.  As technology advanced, MPG standards have been raised several times over many years.  Yes, initially there was a lot of grumbling each time and protests that the new standards were unattainable.  But in the end, innovation prevailed and they were achieved.  Is there any doubt that without such action we’d still be living with the gas-guzzlers of yesteryear?

Best to all,
Stu, K5PB


Title: RE: Ham Xcvrs' and Amps', Transmit Spectral Purity, IMD Products, vs. comm/maritime
Post by: KA4WJA on September 17, 2014, 03:17:05 PM
As usual, my plans have been delayed.....but, at least I've got a good excuse  (elderly family health problems)....

But, I'm still moving forward with my "pie-in-the-sky" / unrealistic idea of letting these various manufacturers know that I will not be buying any new radios from them until they serious improve their transmit IMD figures...

And, a little bit of good news...
I actually stopped 2 fellow hams from buying new Ten Tec Omni VII's, and both of these guys told Ten Tec that they buy new rigs from them when they can produce better transmit IMD specs...

Okay, in the bigger scheme of things, this is realistically not going to make any significant impact.....but, at least I'm trying....


Gotta go...

73,
John,  KA4WJA


Title: RE: Ham Xcvrs' and Amps', Transmit Spectral Purity, IMD Products, vs. comm/maritime
Post by: K6AER on September 17, 2014, 08:20:30 PM
The largest contributer to poor IMD is still the mic gain knob. At some point you will have to remove all knobs from the radio if all signals are to have perfict spectrial purity.


Title: RE: Ham Xcvrs' and Amps', Transmit Spectral Purity, IMD Products, vs. comm/maritime
Post by: DL8OV on September 18, 2014, 07:12:17 AM
Why not remove some of the knobs? It is not too difficult to measure the output of the microphone amplifier with the CPU and adjust the gain accordingly. A DSP looking at the output of the power amplifier can test for increased IMD and/or harmonics and reduce the drive, even if the user turns the knob all the way. It's the 21st Century and about time we used 21st Century solutions to problems like this.

Peter DL8OV


Title: RE: Ham Xcvrs' and Amps', Transmit Spectral Purity, IMD Products, vs. comm/maritime
Post by: ZENKI on September 21, 2014, 03:47:14 AM
We still have hams wanting to let manufacturers off the hook with their poorly designed equipment and then wanting to blame hams who operate the equipment according to the manual. How can you blame hams for inherent  poor IMD and things like ALC overshoot/compression splatter?

We can blame hams for using poor equipment choices like RM Italy CB amps.

We only focus on IMD,  then when we start looking into how noisy and what other products these super expensive  radios are spewing  out, we find that it is not a pretty picture.

k9yc.com/TXNoise.pdf

Jim  has done a good job summarizing the data  for  us. Its a damning indictment  of the poorly designed transmitters from all companies who have faulty equipment.

Look at the top expensive name brand radios, the more expensive they are the dirtier they become. Are we going now call the hams that use these poorly designed equipment LIDS as well?  What we should be doing is writing and complaining about the poor design techniques and  design vetting process that allow such garbage radios onto the market.

The blame game should shift towards the designers and manufacturers. We should move away from blaming hams who operate equipment according to the manual and still cause splatter and emit products that they dont even know that they are emitting. You cant defend the indefensible poor design standards  and equipment  from ham manufacturers today.



Title: RE: Ham Xcvrs' and Amps', Transmit Spectral Purity, IMD Products, vs. comm/maritime
Post by: W3RSW on September 21, 2014, 05:11:11 AM
Interestingly, the rig showing the lowest noise in that report runs 12volt PA's.
And yes, at the bandwidth specified IM was supposed to be included, not just phase noise.

So I wonder what would be shown overlaying a couple of curves, one for IM at a wider frequency spread vs. phase noise for a given set of finals.


Title: RE: Ham Xcvrs' and Amps', Transmit Spectral Purity, IMD Products, vs. comm/maritime
Post by: KA4WJA on September 21, 2014, 07:23:03 AM
Yes, I've read Jim's paper earlier, and it is enlightening...and while his focus is primarily very close-in noise which effects narrow-band modes (such as CW, PSK, etc.), it is a nice paper which should open the eyes of many hams!!
["Compare, for example, the extremely narrow profile of the K3 with the extremely broad profile of the FTDX5000D. When does this matter? In contests, when, for example, a hundred or more legal limit CW stations are trying to fit into the 15 kHz JA window on 160M during a contest!"]


And, it parallel's his talk from last year, for the NCCC...

http://audiosystemsgroup.com/K6XXAmpTalk.pdf


While I don't want to sound like a jerk, I've been using 12vdc PA marine transceivers with excellent transmit spectral purity for about 40 years now (as well as 12vdc PA ham rigs), and over the past 10 years have been using the Icom M-802 (w/12vdc PA), and have been yelling from the tree tops for many years that this adulation of "50-volt PA's" is many times misplaced....
I've been pointing out that the "experts" touting 50-volt PA's, some of whom I admire for their dedication / expertise in specific areas, are unfortunately following a red herring down a rabbit hole (if I mix a few metaphors, to make a point..:)
Please don't get me wrong, there's nothing wrong with higher-voltage solid-state devices....to the contrary, 50-volt, and 24 - 28 volt, PA's can be good....but simply stating that a radio has a 50-volt PA, does not mean that it has a good transmitter....as can be seen by the IMD specs and transmit phase noise specs of many of our ham rigs these days....
Interestingly, the rig showing the lowest noise in that report runs 12volt PA's.
Rick, the gist of this whole discussion here is primarily that....that the manufacturers that advertise heavily (mostly about receiver specs, and bells 'n whistles), and that provide us with the privilege of giving them our hard-earned money, are giving us crap transmitters all the while they have the ability to provide excellent transmitters (even with 12 volt PA's), at a very economical price....but they simply do NOT do so, 'cause we hams don't demand it....

Fact is, 12vdc HF PA's (and entire radios) are currently being made with excellent transmit purity, very economically, by these same manufacturers that market crap transmitters (whether 12v, 28v, or 50v PA's) to us!!
  
If everyone reading these last few postings, read the first postings of the discussion and they'll see what I mean by this...





My understanding (correct me if I'm wrong) is that the scans/data in Jim's paper are of the rigs being keyed at 60-wpm (the ARRL test standard)....and do show the entire single-signal picture (as he heads the table of scans, "Raw Data -- Spectra With CW Keying – Clicks + IMD + Phase Noise")....
Showing the cw-signal's distortions (single-tone distortion is usually referred to as "harmonic distortion", as single-tone IMD is a bit of a misnomer, but it is used by some engineers...), as a 60-wpm cw signal does have bandwidth and as it goes on/off, it's rise time, etc. along with the ocs noise, PA noise, etc. cause distortions, etc.
And yes, at the bandwidth specified IM was supposed to be included, not just phase noise.

So I wonder what would be shown overlaying a couple of curves, one for IM at a wider frequency spread vs. phase noise for a given set of finals.
Again, I may be wrong in my understanding of his paper, but that this what I take from it....


If you look at the two-tone IMD tests of these transmitters, you can see the wideband noise (phase noise, etc.), but since what we are looking at are products outside of the typical SSB passband, the predominant products are the 2-tone IMD products...
For narrow-band discrete modes such as CW, it is the phase noise and keying pattern/shape (primarily rise time), that produce these distortions very close-in...




73,
John,  KA4WJA





Title: RE: Ham Xcvrs' and Amps', Transmit Spectral Purity, IMD Products, vs. comm/maritime
Post by: W1BR on September 21, 2014, 09:41:17 AM
Phase or broadband noise is NOT generated in the finals, nor is determined by the class of operation.  The early stages in a transmitter (especially the VFO or PLL stages) are the contributing factors.  Transmitter noise has nothing to do with IMD, and is present when no modulation exists.


Title: RE: Ham Xcvrs' and Amps', Transmit Spectral Purity, IMD Products, vs. comm/maritime
Post by: KA4WJA on September 21, 2014, 12:13:10 PM
Peter,
While my original, and still primary, focus of this discussion was transmit IMD, and the poor spectral purity of our HF ham transceivers, mainly SSB....
Others have brought up "transmit phase noise",  and CW transmitter bandwidth / purity ("Spectra With CW Keying – Clicks + IMD + Phase Noise"....which in our ham radio community has its primary effect on narrow-band modes like CW...)
 
Whether we call it "transmitter phase noise" (the most common name), "sideband noise", or "wideband noise" (used by some to delineate the transmitter's noise/distortions on constant carrier single-tone non-keyed CW), etc....we are all talking about the transmitter's spectral purity....yes??
 
Phase or broadband noise is NOT generated in the finals, nor is determined by the class of operation.  The early stages in a transmitter (especially the VFO or PLL stages) are the contributing factors.  Transmitter noise has nothing to do with IMD, and is present when no modulation exists.
And, while yes the oscillator stages DO contribute to this noise (hence the name, "phase noise"), there ARE other factors / contributors as well....(otherwise those rigs with excellent receive phase noise specs wouldn't have poor transmit phase noise...)

Remember "noise" thru an amplifier is like signals thru an amp...only worse... :)
The less linear (if that's an acceptable term) the worse...


Have a look at SM5BSZ's work...(although his primary focus was HF transceivers as use as IF's for VHF/UHF/microwave transverters, his initial work is quite informative...)

http://www.sm5bsz.com/dynrange/dubus313.pdf

Quote
The ARRL Laboratory measures reciprocal mixing on the receiver as well as the phase noise of a transmitted carrier. It is commonly assumed that these two quantities are closely related because the receiver and transmitter share the same Local Oscillator which is believed to be the major source of sideband noise; but that is not automatically true. Depending on how well the transmitter is designed,
amplitude noise on the transmitted signals can also be important.

Quote
In Table 1, the Rx@20kHz and Tx@20kHz columns show the receiver reciprocal mixing performance and the transmitter phase noise at an offset of 20 kHz from the carrier frequency (dB below carrier level in ARRL’s standard reference bandwidth of 500 Hz). As stated above, the Rx and Tx figures should ideally be very similar, but the Diff ( = difference) column shows that often they are not. A [pos] figure indicates that the receiver dynamic range for reciprocal mixing is poorer than the sideband noise suppression of the transmitter; a [neg] Diff figure indicates that the transmitter is the better of the two.
 Table 1: Published measurements of transmitter noise and receiver reciprocal mixing. Data are from ARRL Lab measurements [3] (with comparable receiver measurements from Sherwood Engineering where available [4]).


Quote
Table 1 shows that while some transmitters have a sideband noise level at 20 kHz that is compatible with their own good receiver performance, some examples have poor reciprocal mixing performance and the transmitter phase noise may be even worse [6]. The difference in the Tx Wide column, from the best to the worst, is more than 50 dB! Even more remarkable is that this enormous difference between best and worst passes without comment in the text of the ARRL reviews.
SM5BSZ and others have a LOT more great articles / papers on-line....but that's all for now...
http://rfic.eecs.berkeley.edu/~niknejad/ee142_fa05lects/pdf/lect24.pdf http://www.sm5bsz.com/dynrange/dubus313.pdf http://www.sm5bsz.com/dynrange/dubus204/dubus204.htm
http://www.sm5bsz.com/dynrange/dubus205/dubus205.htm



All parts of the transmitter contribute to the transmitter's noise / phase noise / sideband noise / wideband noise, etc., even the PA...
Saying that the PA's are important to the transmitter's IMD purity, but not its other distortions / noise is not true....



But, getting us back to the original discussion....many of your current favorite ham radio manufactures make HF transceivers for other services with excellent transmit spectral purity and low transmit IMD and they do it rather inexpensively!!  (and do it w/ 12-volt PA's)...
So, why do we hams put up with the crappy transmitters they market to us??


73,
John,  KA4WJA


Title: RE: Ham Xcvrs' and Amps', Transmit Spectral Purity, IMD Products, vs. comm/maritime
Post by: W3RSW on September 21, 2014, 12:44:25 PM
John, I was typing away on an iPad while you were making your remarks, hence overlap.

 CW generated by switching an RF wave off and on is really a seris of pulsed square waves. - - w/Infinite harmonics that need to be tamed by integration.   Real world components tame these harmonics somewhat by virtue of real wire and component resistance, capacitance, etc. Let me think about this awhile.

Some intermediate stages be they RCL circuits or even an output tank of a single Osc. Transmitter are expected to more fully tame the square waves.  Apparently the K3's keyed waveform achieves just the right balance between legibility and damping through its various stages. Yes phase noise is usually spec'd for oscillators and clocks but every stage contributes noise, usually compositly less relatively speaking as the signal progresses through the chain.

All the final devices have spec sheets hopefully showing IMD specs , such IMD being the major contributor for Degradation of signals in those final stages, assuming correct operating practice. The final devices are expected to faithfully amplify all preceding signal ( junk and all) withing their class (ab 1,2) abilities and with varying bias constraints. Here is where good design comes in in a whole host of device and set point characteristics.

Pulsed CW at 60 wpm is modulation and will, just like a tamer 60hz audio tone modulating an RF carrier generate IMD, 2nd, 3rd, 4th, etc. harmonies more severe than an sine wave audio tone.
Of course in a PP final the even harmonics will be attenuated.

As for IM not being generated unless modulation is present, then there is no communication, ergo how would the 100 stations transfer intelligence in the 15kHz contest space anyway. I posit that any signal, even unmodulated lowly noise generated by black box resistance, the lowest generator possible will generate products, etc. when amplified by an oscillator not to mention possibly numerous following stages.

Still thinking. I'm attempting to tie to information theory here.  ;D

The fact that nothing but phase noise is heard is modulation and information is received by virtue of it being there vs. nothing.



Title: RE: Ham Xcvrs' and Amps', Transmit Spectral Purity, IMD Products, vs. comm/maritime
Post by: G3RZP on September 21, 2014, 01:28:17 PM
Before we go overboard, just how far down do IMD and phase noise need to be at HF? Different matter at VHF/UHF, I know.

If we had data on the average signal level received, signal to noise ratio and the spread in terms of deviation, we could figure out how much improvement is needed to cover say 90% of splatter cases - and from that how much such improvement costs.

To improve for the sake of improving when no benefit can be demonstrated is poor engineering. The ham on Bouvet or South Georgia is far enough away it makes no odds what his IMD is like! In Chicago, it may well be another matter...


Title: RE: Ham Xcvrs' and Amps', Transmit Spectral Purity, IMD Products, vs. comm/maritime
Post by: W3RSW on September 21, 2014, 02:11:34 PM
But that's half the fun, going underboard. 
Well we certainly don't have to go down to Plank limits.

Seriously, if I understand you, Yes your correct  in asking what is the composit detriment of many signals with trash products on a typical window of operating at a given freq.? ...the superposition of many poor signals conspiring to algebraicly (or worse) add enough trash to degrade minimally powered and desired signals.  Call that Wilson's rogue wave theory, hehheh.
Well, I expect you'll prick that bubble.

Over designing is not necessarily poor engineering but is poor economics.  And somehow the limits of design practice have to be established, if by no other way than experimentation.
..not gonna drag out everything I don't know about empirical design.  ;D


Title: RE: Ham Xcvrs' and Amps', Transmit Spectral Purity, IMD Products, vs. comm/maritime
Post by: G3RZP on September 21, 2014, 02:33:12 PM
We do know that for many years, commercial point-to-point  ran ISB with IMD products in the opposite sideband 36dB down. Now how many signals on 20m for example are really S9? With -36dB IM products, their splatter would be S3......

So let us say we wanted all IMD -48dB. In a quiet rural radio noise area, on 7 MHz, the median ITU noise level as received on a dipole is about -107dBm in an SSB bandwidth. So with -48dBm IM products, the signal would have to be -59dBm or 14dB over S9 (50 microvolts or -73dBm) before the IM product came out of the noise.......Even at -36dB, the signal would need to be just over S9 to get the IM products out of the noise. Plus, usually, for signals to be that strong the noise level is higher...

So yes , many modern rigs are very poor, as I showed in my lecture at the RSGB Convention last year. (I am considering offering it to the W9DXCC meeting next year). But there comes a point where improving doesn't actually pay any practical dividends.

W3RSW said "Over designing is not necessarily poor engineering but is poor economics."

He is so right.....

The novelist and aeronautical engineer Neville Shute Norway once said "An engineer is a man who can do for ten shillings what any fool can do for a pound".......there is some truth in that.


Title: RE: Ham Xcvrs' and Amps', Transmit Spectral Purity, IMD Products, vs. comm/maritime
Post by: KA4WJA on September 21, 2014, 02:38:29 PM
Peter,
Four months ago, when I started this discussion about transmit IMD, I stated my opinion that our ham radio HF transmit IMD should be at least as good as those of the maritime service (FCC Part 80 and ITU specs)....and hopefully even better!!
And, I pointed-out clearly that this is not only economically doable, but IS being done by some of these same manufacturers...

Now, I don't wish to drift about in the realms of "phase noise phantasy"...:)
So, I won't go down that discussion path here (perhaps someone else could start a new thread, where the effects of phase noise can be fully phlushed out...:)

But, as for HF transmit IMD...particularly on the HF phone bands...my thoughts have not changed...our ham radio HF transmit IMD should be at least as good as those of the maritime service (FCC Part 80 and ITU specs)....and hopefully even better!!

I do not have first-hand experience of what the bands are like in the UK...but here in the US, where single-hop signals are very strong, there is a LOT of crap coming out of these stations....(note: "crap" is an American scientific term that some of you may not be familiar with.. :)
And, yes....some of this is caused by too much mic gain and amplifiers being over-driven.....but even barefoot stations without "screaming" audio have horrible transmit products...(and the local NVIS signals in the wintertime are sometimes so full of splatter that you need to move 20+ kHz away....summertime evenings the atmospheric noise usually covers up most of their splatter...)  
Before we go overboard, just how far down do IMD and phase noise need to be at HF? Different matter at VHF/UHF, I know.

If we had data on the average signal level received, signal to noise ratio and the spread in terms of deviation, we could figure out how much improvement is needed to cover say 90% of splatter cases - and from that how much such improvement costs.

To improve for the sake of improving when no benefit can be demonstrated is poor engineering. The ham on Bouvet or South Georgia is far enough away it makes no odds what his IMD is like! In Chicago, it may well be another matter...


So, I stand 100% my original thoughts.....that we should demand that our ham radio HF transmit IMD should be at least as good as those of the maritime service (FCC Part 80 and ITU specs)....and hopefully even better!!


Sorry don't have the time to delve into specifics....oppsss, I already did that 4 months ago....look at the first page of this discussion...

Gotta' go...


73,

John,  KA4WJA


Title: RE: Ham Xcvrs' and Amps', Transmit Spectral Purity, IMD Products, vs. comm/maritime
Post by: G3RZP on September 21, 2014, 02:50:30 PM
John,

I can't import powerpoint slides..

I have some that show if you use two tones  of 1100 and 1700 Hz (standard for European maritime radio standards) and 400 and 2500 Hz, in the first case the average amateur transmitter placed on the market between 200 and 2013 is 10dB better, while in the second case, the average amateur tx in the second case is 1dB worse out to 4.6kHz away and was better by 10dB further out.

Now note that is the AVERAGE amateur transmitter and I don't readily have the details of the spread. It is all derived from ARRL reports, so we don't know the production spread on individual equipments either, but it is a guide.

I can send you the plots if  you give me an email - or a method to put a .pps slide on here!

BTW, where are the ITU recommendations on their website or referenced in the RRs?

73

Peter G3RZP


Title: RE: Ham Xcvrs' and Amps', Transmit Spectral Purity, IMD Products, vs. comm/maritime
Post by: KA4WJA on September 21, 2014, 05:00:23 PM
I don't have my references down here with me this week....so, I I'm relying on just memory and what I have in my laptop....
And, while "tones" are the way most testing is done, I prefer white noise testing, rather than "tones"....


The old FCC Part 80 specs were relaxed some years ago (1990's I think), to conform to the new ITU Maritime specs....
Here is the old FCC Part 80 mask (for SSB)....(I wish we had transmitters like this, these days!)

(http://i62.tinypic.com/scrw4g.jpg)

For SSB comms, the passband is 2.8khz, max.. (2K80J3E)

That's all emissions +/- 1.9khz from center freq (NOT from edge of passband) to be down 40dbc, that's -40dbc, 3.8khz wide....
All emissions +/- 2.8khz from center freq to be down 50dbc
All emissions +/- 7.0khz from center freq to be down 60dbc
All emissions +/- 11.2khz from center freq to be down 80dbc
And, all emissions more than 5% away from center freq to be down 100dbc
Note these are -dbc, not referenced to PEP....so add 6db to compare to the ARRL test figures!!!
Modern commercial maritime radios can meet most of these old specs (yes, the M-802 meets them, up until the -75dbc point).....but the -80dbc is tough at +/- 11khz, and the -100dbc at > 5%, is pretty tough as well...

And, no K3 or Class A Yaesu, comes close!!



The new FCC Part 80 spec / mask conforms to the ITU maritime standard....
(which I see quoted as -36dbc 3rd order IMD....but the actual spec and mask are more controlling...)
And, any new "ham radio standards" should take into account both the "spec" and "spectral mask"!!

This spec of 43+10LOG(pX)  of course allows for "dirtier" transmitters of lower power, and requires cleaner transmitters as the power goes up....(which if allowed to be manipulated by ham radio manufacturers, would give us lots of low power radios and hams clamoring for RM Italy amps!!!! God help us!!!)

(http://i57.tinypic.com/a3lgu0.jpg)

On this scan of the Icom M-802, you see the current FCC Part 80 (and ITU) spectral mask....note how relaxed it is, and quite easy to make even 12vdc PA's to comply to...but ham radio HF transceiver don't...

Remember, despite the recent comments about its transmit phase noise, the K3's transmit IMD specs (according to the ARRL) are:
3rd order = –29db PEP (-23dbc)
5th order = –43db PEP (-37dbc)
7th order = –46db PEP (-40dbc)
9th order = –51dB PEP (-45dbc)

(that's about 15db+ worse than even the current Part 80 specs, see mask on this scan)
(http://i57.tinypic.com/a3lgu0.jpg)



The above ARE the current FCC Part 80 and ITU Maritime specs...
As for "where" on-line to find the detailed ITU and FCC specs....I'd try Google and see if the ITU has 'em in the online Radio Regs, etc...



73,

John,  KA4WJA


Title: RE: Ham Xcvrs' and Amps', Transmit Spectral Purity, IMD Products, vs. comm/maritime
Post by: G3RZP on September 22, 2014, 02:44:13 AM
The ITU-R Rec is M1173-1. Looking at tests that have been published, a lot depends on what tone frequencies you use: 1100 and 1700Hz aren't that hard to meet the masks, but 400 and 2500 are a different kettle of fish....

Numbers I dug out of over 100 published reviews of amateur transmitters......

Looking back at the last generation of tube PA transceivers, the average of their performance from 1973 to 1983

3rd order -36dB   5th order -44dB   7th order -58dB   9th order >-66dB wrt PEP

The average values for solid state transceivers since 2000

3rd order -30dB   5th order -41dB   7th order -47dB   9th order >-52dB   wrt PEP

What does stand out is not only the worse close in products, but the far worse high order products which can interfere further away....but these are numbers averaged over lot of reviews and there is a quite a spread on them. A number of the more modern rigs have appreciable products of 11th and even 13th order.....

I also note that in a few cases, numbers for an equipment in one review and numbers in another review don't always line up even the test methods are similar. Which suggests to my mind that you can have an appreciable spread between equipments.....which could be just the normal semiconductor tolerances or things being pushed a bit too hard.

Now you can see why I use a rig with 6146Bs in the PA!


Title: RE: Ham Xcvrs' and Amps', Transmit Spectral Purity, IMD Products, vs. comm/maritime
Post by: KH6AQ on September 22, 2014, 03:51:12 AM
Directly averaging decibels can cause large errors. Decibels must first be converted to linear units, averaged, and converted back to decibels.


Title: RE: Ham Xcvrs' and Amps', Transmit Spectral Purity, IMD Products, vs. comm/maritime
Post by: AA4HA on September 22, 2014, 12:13:21 PM
I have been reading ARRL test lab results for many years. They will show their little red-yellow-green bar graphs and you can clearly see the "stinkers" in the mix but the ARRL lab summary will soft-shoe those problems. They will speak in glowing terms about some technically minor benefit like a multi-colored LCD display or the benefits of an eight pin microphone connection.

Lots of hams read those reports but because the test results are not clearly explained as to what the implications are for our spectrum, most hams just ignore the little colored bar graphs.

I bet the ARRL labs have never said that a radio has "failed". Unfortunately the commercial implications of advertisers is #1.

I am a dues paying member and I pay for the magazine and even buy books from the ARRL website (as many others do). Yet most amateurs are not being told of what makes a truly good transmitter or receiver (or amp). We should be pushing our hobby to constantly progress technologically, this does not mean how many knobs a radio has or how many watts (or should we start calling them "pills" or "bird-watts"?).

Come on folks, we buy this gear! A full fledged contest grade transceiver can cost upwards of $4-6K. We should expect more, we should expect better. Maybe then the manufacturers will spend even half as much on the design of the RF deck as they do on the front panel.


Title: RE: Ham Xcvrs' and Amps', Transmit Spectral Purity, IMD Products, vs. comm/maritime
Post by: DL8OV on September 22, 2014, 12:32:15 PM
"For SSB comms, the passband is 2.8khz, max.. (2K80J3E) That's all emissions +/- 1.9khz from center freq (NOT from edge of passband) to be down 40dbc, that's -40dbc, 3.8khz wide.... "

Given that voice information is supposed to occupy the frequencies from 300 Hz to 3000 Hz (2,7 KHz) I can see where they get that figure of 2,8 KHz from. However, please could someone explain to me how Bob Heil makes a living selling communications quality microphones that produce audio outside these frequencies?

Peter DL8OV

P.S. I agree 100% with Ms Hayes.


Title: RE: Ham Xcvrs' and Amps', Transmit Spectral Purity, IMD Products, vs. comm/maritime
Post by: KA4WJA on September 22, 2014, 01:35:37 PM
Tisha,
I'm with 'ya 100%!!
Come on folks, we buy this gear! A full fledged contest grade transceiver can cost upwards of $4-6K. We should expect more, we should expect better. Maybe then the manufacturers will spend even half as much on the design of the RF deck as they do on the front panel.
I started this discussion to effect just this change...to spur my fellow hams into demanding more for the $$$$ that they spend....and I've already gotten 2 of my nearby fellow hams to NOT buy new rigs this summer...
(and I think I showed that there are affordable, high-perf, HF rigs w/ excellent transmit spectral purity, made by these same manufacturers, so we KNOW they can not only design and build the radios better, but that they ARE also selling them to users who require them to be better...)





As for the ARRL...well, don't get me started.... :)
I joined the ARRL in 1974, and except for a one-year lapse, I've been a member ever since....and yes, I do buy a new handbook and antenna book, every 5 years or so...

My most recent frustration was a series of e-mails and phone calls between Dave Summer and I....
I brought to their attention, a week ahead of time, info on an official PUBLIC  meeting in NYC, discussing communications problems and solutions arising for emergencies / disasters (specifically "superstorm Sandy") w/ both FEMA, FCC, NY, NJ, CT officials, together with wireless / teleco industry leaders as well as representatives from citizens and "community leaders"....
It was open to the public and the public was encouraged to attend and comment....

Now, I'm >1000 miles from NYC...and I had many constraints on my time...but, I thought that since it is just a short drive from Newington, CT that the ARRL would send someone to "advertise" the facts that "Ham Radio" fulfills its duties and requirements in every disaster, and to remind all those from the FCC, etc. (and the"Telco's") just what out precious spectrum is being used for!!
A GREAT opportunity for good PR and to get the FCC to remember why we need the spectrum we do..

Well, the ARRL's response was:
"what would we go to that meeting for?"
And, after I explained my thoughts, I was "reminded" that the ARRL has direct contacts with the FCC and there is no need to bother them at a Public Meeting...
And, when I asked if they (ARRL) would send a e-mail bulletin out to their members in the NYC area, asking them to attend...I got no further response to calls / e-mails...
True story!!
 
 I have been reading ARRL test lab results for many years.  

Lots of hams read those reports but because the test results are not clearly explained as to what the implications are for our spectrum, most hams just ignore the little colored bar graphs.

I bet the ARRL labs have never said that a radio has "failed". Unfortunately the commercial implications of advertisers is #1.
So, I'm not holding my breath that the ARRL will ever doing anything approaching declaring a radio a "failure" for having poor transmit spectral purity....but we can dream! :)





Peter, please remember that that first mask and my words describing it, was the old Part 80 spec, which was changed/relaxed in the 90's....so no longer applies...
(but, look high tight it was....oh, to have that gain..:)

The new FCC Part 80 spec [ 43+10LOG(pX)  ], 3rd order -36dbc,  and the second mask (the mask over the scan of the Icom M-802) is what applies now...
And, for 2K80J3E, the max passband is 2.8khz...(all transmit energy should be within that passband, which I seem to recall means 99% ???, the rest must fall within the spec / mask...)
 
"For SSB comms, the passband is 2.8khz, max.. (2K80J3E) That's all emissions +/- 1.9khz from center freq (NOT from edge of passband) to be down 40dbc, that's -40dbc, 3.8khz wide.... "

Given that voice information is supposed to occupy the frequencies from 300 Hz to 3000 Hz (2,7 KHz) I can see where they get that figure of 2,8 KHz from. However, please could someone explain to me how Bob Heil makes a living selling communications quality microphones that produce audio outside these frequencies?
Most of my rigs have 2300hz - 2400hz SSB filters for transmit and receive...and the typical response is from 300hz to 2600/2700hz...

Now, Bob Heil is a fun guy, an audiophile, and an accomplished musician....(he is a close/dear friend of a late close friend of mine)
But, I do not keep up with what he's been selling/marketing lately...
The last I looked (> 10 years ago), he was selling the HC-4 and HC-5 elements, which I thought were communications grade mic elements....one was a narrow response mic, tailored for contesting/dx'ing, with a slight boost in higher end (2000hz if I recall correctly),  and the other was a wider-response mic, tailored more for the average rag chewer....
But I don't keep up with what he's selling nowadays...
Although with all those ESSB and Hi-FI SSB guys, as well as all those with SDR's, etc. maybe he's selling what the customer demands???
(you know what P.T. Barnum said...."there's a sucker born every minute.")






Now can someone enlighten an old ham like myself, as to what benefit an 8-pin mic plug would actually be, to me??? :)
They will speak in glowing terms about some technically minor benefit like the benefits of an eight pin microphone connection.




73,
John,  KA4WJA


Title: RE: Ham Xcvrs' and Amps', Transmit Spectral Purity, IMD Products, vs. comm/maritime
Post by: K2GWK on September 24, 2014, 06:11:33 AM
I have been reading ARRL test lab results for many years. They will show their little red-yellow-green bar graphs and you can clearly see the "stinkers" in the mix but the ARRL lab summary will soft-shoe those problems. They will speak in glowing terms about some technically minor benefit like a multi-colored LCD display or the benefits of an eight pin microphone connection.

Lots of hams read those reports but because the test results are not clearly explained as to what the implications are for our spectrum, most hams just ignore the little colored bar graphs.

I bet the ARRL labs have never said that a radio has "failed". Unfortunately the commercial implications of advertisers is #1.

I am a dues paying member and I pay for the magazine and even buy books from the ARRL website (as many others do). Yet most amateurs are not being told of what makes a truly good transmitter or receiver (or amp). We should be pushing our hobby to constantly progress technologically, this does not mean how many knobs a radio has or how many watts (or should we start calling them "pills" or "bird-watts"?).

Come on folks, we buy this gear! A full fledged contest grade transceiver can cost upwards of $4-6K. We should expect more, we should expect better. Maybe then the manufacturers will spend even half as much on the design of the RF deck as they do on the front panel.

Make no mistake this is not an ARRL problem. While this thread is extremely well intentioned it is missing the mark. Until the FCC changes it's IMD spec manufacturers will only design to meet the spec. From the manufacturers perspective, why would I throw money in to R&D to design something that far exceeds the specification? The Non Recurring Engineering costs involved in far exceeding the FCC's IMD spec will be priced in to the product which may make the product non price competitive. I bet it would make a much easier pill for the manufacturers to swallow if they were forced into improve their IMD specs by the FCC changing the spec because it would be a level playing field forcing all manufacturers to engineer better IMD in to their products.


Title: RE: Ham Xcvrs' and Amps', Transmit Spectral Purity, IMD Products, vs. comm/maritime
Post by: G3RZP on September 24, 2014, 08:03:26 AM
I am very much against making this a regulatory matter. For many years, in general, there were no standards for spurious emissions other than 'thou shalt not cause interference' - and there were very few cases where there was a problem - less, in fact, than for other services with definite standards. Internationally,  spurious emission requirements only came in because some Administrations at ITU-R TG1/3 wanted to 'tidy things up' and include amateurs.

How you use the majority of transmitters affects the splatter, and that is very hard to regulate. Possibly having a higher technical standard for getting a licence would be more useful, but the FCC could tighten up requirements and see the rest of the world ignore them - which could mean more expensive equipment in the US - and a black market in imports. After all, the FCC have not been too successful in keeping illegal CB powers down, and they do not have the resources to start chasing hams - or, it seems from a thread in Misc on eham.net, collecting any NALs anyway.

There's little point in rules that are either not enforced or that cannot be enforced without providing resources - which means money - that is not available.


Title: RE: Ham Xcvrs' and Amps', Transmit Spectral Purity, IMD Products, vs. comm/maritime
Post by: AA4HA on September 24, 2014, 10:29:36 AM
How you use the majority of transmitters affects the splatter, and that is very hard to regulate. Possibly having a higher technical standard for getting a licence would be more useful, but the FCC could tighten up requirements and see the rest of the world ignore them - which could mean more expensive equipment in the US - and a black market in imports.
Too bad customs inspectors are as not as rigorous in inspecting incoming packages or commercial goods for compliance with our laws. If you carried an amplifier in the trunk of your car across the US/Canadian border you could be held up for days (or just lose your item) if there was not an FCC compliance tag.

Maybe if a few Conex containers were taken off the docks and sent right to the shredder there would be such an uproar. Unfortunately someone would say that we are being unfair and starting a trade war. So we would give advance notice, that in X number of days, every electronic device will be inspected (and some sampling actually tested) for compliance. This would not be just on electronics but include pet foods and dairy products for things like melamine contamination, tilapia for mercury PCB's or DDT content, formaldehyde in plastics, lead in paint or radioactive materials in table legs.

(BTW, every one of those examples has happened)

<smile> it might put Wally-World out of business.


Title: RE: Ham Xcvrs' and Amps', Transmit Spectral Purity, IMD Products, vs. comm/maritime
Post by: G3RZP on September 24, 2014, 11:42:31 AM
Tisha,

So you have an amp rated at 1kW at XdB IMPS - whatever X is - and it can be driven to 1500 watts - which in practice it almost certainly can - and it's a lot less than X dB. So how do you legally prevent its sale?

Plus where do you get the customs guys with the necessary technical qualifications from?

Just doesn't work in practice.....


Title: RE: Ham Xcvrs' and Amps', Transmit Spectral Purity, IMD Products, vs. comm/maritime
Post by: K2GWK on September 26, 2014, 07:15:54 PM
I am very much against making this a regulatory matter. For many years, in general, there were no standards for spurious emissions other than 'thou shalt not cause interference' - and there were very few cases where there was a problem - less, in fact, than for other services with definite standards. Internationally,  spurious emission requirements only came in because some Administrations at ITU-R TG1/3 wanted to 'tidy things up' and include amateurs.

How you use the majority of transmitters affects the splatter, and that is very hard to regulate. Possibly having a higher technical standard for getting a licence would be more useful, but the FCC could tighten up requirements and see the rest of the world ignore them - which could mean more expensive equipment in the US - and a black market in imports. After all, the FCC have not been too successful in keeping illegal CB powers down, and they do not have the resources to start chasing hams - or, it seems from a thread in Misc on eham.net, collecting any NALs anyway.

There's little point in rules that are either not enforced or that cannot be enforced without providing resources - which means money - that is not available.

Correct me if I am wrong but it doesn't appear that the manufacturers are in a hurry to improve their IMD performance and hams are certainly not boycotting the manufacturers because of IMD issues. You are correct that this is a global problem not just a US problem. Even if things change here in the US there is no guaranty that the rest of the world will follow suit.


Title: RE: Ham Xcvrs' and Amps', Transmit Spectral Purity, IMD Products, vs. comm/maritime
Post by: G3RZP on September 27, 2014, 12:45:31 AM
The rigs that showed a BIG improvement were the Yaesu ones which could run the PA in Class A at reduced power. But it would appear that they weren't that popular since Yaesu doesn't offer that facility any more.


Title: RE: Ham Xcvrs' and Amps', Transmit Spectral Purity, IMD Products, vs. comm/maritime
Post by: K2GWK on September 27, 2014, 05:18:56 AM
The rigs that showed a BIG improvement were the Yaesu ones which could run the PA in Class A at reduced power. But it would appear that they weren't that popular since Yaesu doesn't offer that facility any more.

I agree, I believe the FT1000MP could run in class A. I have two class A space heaters in my family room as part of my stereo. I built a clone of an Nelson Pass Aleph 2 as mono blocks. During the winter it is nice and toasty in the family room when listening. In the summer it just gets too hot to run for extended periods. The Alephs are pretty inefficient and each dissipates over 300 watts in heat to produce the 100 watt output. Running the HF amp in the FT1000MP in class A reduced the power from 200 watts output to 75 watts IRRC. It is very difficult to get Hams to buy into reducing power but there was less much less IMD when biased as class A.


Title: RE: Ham Xcvrs' and Amps', Transmit Spectral Purity, IMD Products, vs. comm/maritime
Post by: ZENKI on September 27, 2014, 07:07:52 AM
The latest Yaesu FT5000 has the Class Bias option. You can even vary the bias in class AB for less heat and better linearity.. The Yaesu has the silly ALC  compression design fault which ruins IMD performance in Class A. The Icom radios  have this same design fault. Even the IC7800 can generate ALC splatter.

ALC compression when used with Tetrode and Solid state amplifiers can  cause some really bad buck shotting. I hear lot of FT5000's Quadra combinations whose IMD performance is very bad only because of  ALC compression generated IMD. You will not find compression generated IMD problems on any commercial HF radio.

Maybe the ARRL will start testing for this issue in the future. The RSGB has  just reviewed the Flex6500 and its IMD performance for a 12 volt FET amp appears to very good. It probably has  the best IMD figures that I have seen for a recently reviewed transmitter. If Adaptive pre-distortion was applied to the Flexradio   6500 it would be perfect. The Anan 100 was also reviewed and it had relatively poor IMD performance that is typical of  most transmitters. When puresignal was enable it improved dramatically. The essential point  is that the inherent  IMD before pre-distortion is  applied should be designed to deliver the best possible IMD performance. This  would ensure that when pre-distortion is applied the final result will be fantastic. Its good seeing that the Flexradio 6xxx has such  good IMD performance for a 12 volt radio. I dont know when we will see a very clean radio from the Japanese manufacturers, probably  never.


The rigs that showed a BIG improvement were the Yaesu ones which could run the PA in Class A at reduced power. But it would appear that they weren't that popular since Yaesu doesn't offer that facility any more.

I agree, I believe the FT1000MP could run in class A. I have two class A space heaters in my family room as part of my stereo. I built a clone of an Nelson Pass Aleph 2 as mono blocks. During the winter it is nice and toasty in the family room when listening. In the summer it just gets too hot to run for extended periods. The Alephs are pretty inefficient and each dissipates over 300 watts in heat to produce the 100 watt output. Running the HF amp in the FT1000MP in class A reduced the power from 200 watts output to 75 watts IRRC. It is very difficult to get Hams to buy into reducing power but there was less much less IMD when biased as class A.


Title: RE: Ham Xcvrs' and Amps', Transmit Spectral Purity, IMD Products, vs. comm/maritime
Post by: G3RZP on September 27, 2014, 09:00:21 AM
ALC is very much shutting the stable door after the horse has bolted. Add to that business of overshoot because the ALC is used for power setting rather than attempting to grab peaks that cause overload - which was what it was originally intended to do.

From which you can figure that I don't like ALC!

But I still question just how far down the low order products need to be, although the high order ones are generally far too high.


Title: RE: Ham Xcvrs' and Amps', Transmit Spectral Purity, IMD Products, vs. comm/maritime
Post by: K5PB on September 28, 2014, 03:38:16 PM
I've been following the posts in this thread with great interest, and it seems to me there is general agreement that something should be done.  Not surprisingly, there is much less agreement on how best to go about it.  This is my attempt to summarize the issues so far, and to suggest further action.

To put the transmit IMD problem in perspective, I believe we should be thinking in terms of spectral energy across the phone bands.  During periods of high activity, the simultaneous energy distribution from large numbers of transmitters could be compared to band-wide noise loading (no pun intended).  If average transmitter IMD products were reduced by, say 8-10 dB (an attainable number), here is a practical way to look at it: the average reduction in QRM levels would be between 1 and 2 S-units.  Is there anyone who wouldn't like to see that happen?

It has been argued that reduction in IMD through regulation is not the answer.  A gentleman whose knowledge and experience I respect has pointed to years gone by, saying "...there were no standards for spurious emissions other than 'thou shalt not cause interference' - and there were very few cases where there was a problem."  I agree with his facts, but not his premise.  Times have changed; band occupancy is much, much higher, power levels are up, and civility is down.  In those days if someone told us we were splattering, we either courteously turned down the gain or shut down entirely to figure out what was the problem.  A clean signal was a source of pride. Today we are just as likely to receive an irritable response such as, "It's your lousy receiver, idiot," and no corrective action by the offender.

Another argument against tighter regulation has been that these miscreants, through ignorance or intent, will undo any improvements attained through regulation.  That in my opinion is specious.  Yes, such "lids" have always been with us, and no doubt always will be, but thank heaven they are still in the minority.  And it should be kept in mind that an inherently cleaner transmitter will remain relatively cleaner even when misused.

Yet another argument has been that getting improved standards will take too long.  As pointed out by John KA4WJA early in this thread, it may be a long process.  But does that mean we should merely talk about the problem, wring our hands, and do nothing?  I think not.  I'm reminded of the very important work done by Rob Sherwood NC0B on strong-signal receiver performance going back at least 10 years.  His website tables of receiver performance and his presentations to clubs and major conventions have been seen and heard by thousands of hams.  Yet it has been only in the last 3 to 5 years that major
improvements have been made in receiver performance.  Isn't it time we got moving on the transmit side?  Or as John Wayne famously used to growl, "We're burnin' daylight !!"

As I have suggested earlier (post #56) and K2GWK has clearly expanded on (post #77), it is extremely doubtful in today's competitive market that any transceiver manufacturer will take action on its own.  As a group they would prefer a set of standards applying to all.  Therefore, the question remains, how do we best initiate action?

Frankly, I doubt that we can look to ARRL HQ. The leadership seems too entrenched, complacent, and fearful of potential adverse impact on advertising revenue. But the ARRL Board is another matter.  As elected officials, the Division Directors have to be sensitive to constituents and their concerns, or face possible loss of office.  You can contact your Division Director on your own, but perhaps an even more effective approach is to get your club to pass a resolution requesting ARRL Board action on this problem.  In short, numbers count.

If we who are concerned about this issue can start a wave, I think we will ultimately be successful, although it probably won't be overnight.

Best to all,
Stu, K5PB
ARRL Life Member
Collins Radio, Ret.








Title: RE: Ham Xcvrs' and Amps', Transmit Spectral Purity, IMD Products, vs. comm/maritime
Post by: G3RZP on September 29, 2014, 02:33:41 AM
I think, with respect to K5PB, that the problem is not only the level of activity but the high order IMD products that are so much worse with current solid state PA stages. Whereas the last tube rigs had 3rd order products around -35 to -40dB, 5th order around -50dB and 7th order around -60dB, the majority of modern rigs run around -30dB for third order, -35 to -40dB for 5th order,  -45dB for 7th order, -55dB or so for 9th order.

This means that the amount of cumulative IMD noise further away from the signal is much greater.  For the usual SSB bandwidth, it means that on USB, the 'spitch' 10kHz higher than the nominal carrier frequency is around -55dB (on LSB, 10kHz lower). That's bad enough but if you factor in K5PB's activity factor, you can understand why there is an increasing problem. At the same time, for many amateurs, the amount of electrical noise from the various things like SMPS, TV sets, computers and so on is raising the noise floor such that the increase caused by the high order IMD products is not so noticeable.

It then becomes necessary to determine how much improvement is necessary. It would be a good start to aim for performance, especially high order IMD, equal to the last generation of tube rigs......


Title: RE: Ham Xcvrs' and Amps', Transmit Spectral Purity, IMD Products, vs. comm/maritime
Post by: W1BR on September 29, 2014, 04:26:17 AM
ALC is very much shutting the stable door after the horse has bolted. Add to that business of overshoot because the ALC is used for power setting rather than attempting to grab peaks that cause overload - which was what it was originally intended to do.

From which you can figure that I don't like ALC!

But I still question just how far down the low order products need to be, although the high order ones are generally far too high.

And add a modern amp that might only need 35 watts to reach full legal output power, and a 200 watt rig with overshoot and a user who uses the ALC for a cheap speech processor.

Pete


Title: RE: Ham Xcvrs' and Amps', Transmit Spectral Purity, IMD Products, vs. comm/maritime
Post by: DL8OV on September 29, 2014, 04:34:37 AM
Rather than adopt the government/regulation route is it worth approaching the manufacturers en masse to demand 1) Cleaner and better designed transmit strips and 2) Tight microprocessor control of settings so that is is impossible for the operator to overdrive the transmitter, both at the audio and RF stages?

A rig with a shaft encoder behind each control means that the CPU is already in charge, adding moderation to operator settings is just a matter of software.

Peter DL8OV


Title: RE: Ham Xcvrs' and Amps', Transmit Spectral Purity, IMD Products, vs. comm/maritime
Post by: W3RSW on September 29, 2014, 06:18:39 AM
Apache Lab's predistortion techniques and the inevitable march to DDC SDR's inside every YeaIcomWooXcom may make all the wailing and gnashing moot.

And btw software can be manipulated too, mike gain and all. 

Flanging Guitars obviously satisfy some human need or other. (Intended distortion to be as loud and in your face as the amplifier's ability without meltdown.)
  Messing with someone else's fun had always been the dark side of human nature.
     -Perhaps even an essential side to prevent stagnation and if nothing else as a vehicle to show
     difference and  paths to improvement.
   


Title: RE: Ham Xcvrs' and Amps', Transmit Spectral Purity, IMD Products, vs. comm/maritime
Post by: K5PB on September 29, 2014, 12:59:35 PM
I believe Peter G3RZP (post #87) and I are in basic agreement, although we may differ on a few details.  My example based on band-wide spectrum loading was admittedly simplistic in order to make a broadly practical point.  Of course, the devil is in the details, and one of the devils in this case certainly is the excessive levels of high-order IMD common to current solid-state finals.  Deficiencies mentioned by others such as overshoot and misuse of ALC also contribute to the overall problem. 

But, being practical, let's return to the example presented by John KA4WJA (original post) of the IMD spectra of a current Icom marine transceiver with 12v solid-state finals.  If design techniques and components used there can be economically adapted to amateur transceivers (and on the surface, at least, it appears that they can) with the same end results, the problem of both low and high-order IMD is solved. 

Those numbers are as good or better than those of nearly all tube rigs of yesteryear.  And I believe that is the point John was trying to make.  Could advancing technology make them even better?  Possibly, maybe even probably,  But believing in the art of the possible, for now they're good enough for me -- and a major step forward.

Like many others, I too dislike governent regulation and the Orwellian big-brotherism it too often represents.  But given the known propensities of manufacturers and their desires for a level playing field -- and again being practical -- I believe the regulatory route presents the shortest, and perhaps fastest, path to a solution.  Going it alone as suggested by DL8OV, while altruistic and commendable, raises the question how and by what avenues?  Given the independence of thought by the amateur community at large, that could turn out to be like herding cats.

At this point I'm encouraged by all the good thought and ideas expressed in this thread.  I believe we are gradually converging on some kind of consensus.

Best to all,
Stu, K5PB


Title: RE: Ham Xcvrs' and Amps', Transmit Spectral Purity, IMD Products, vs. comm/maritime
Post by: K2GWK on September 29, 2014, 01:54:28 PM
I believe Peter G3RZP (post #87) and I are in basic agreement, although we may differ on a few details.  My example based on band-wide spectrum loading was admittedly simplistic in order to make a broadly practical point.  Of course, the devil is in the details, and one of the devils in this case certainly is the excessive levels of high-order IMD common to current solid-state finals.  Deficiencies mentioned by others such as overshoot and misuse of ALC also contribute to the overall problem.  

But, being practical, let's return to the example presented by John KA4WJA (original post) of the IMD spectra of a current Icom marine transceiver with 12v solid-state finals.  If design techniques and components used there can be economically adapted to amateur transceivers (and on the surface, at least, it appears that they can) with the same end results, the problem of both low and high-order IMD is solved.  

Those numbers are as good or better than those of nearly all tube rigs of yesteryear.  And I believe that is the point John was trying to make.  Could advancing technology make them even better?  Possibly, maybe even probably,  But believing in the art of the possible, for now they're good enough for me -- and a major step forward.

Like many others, I too dislike governent regulation and the Orwellian big-brotherism it too often represents.  But given the known propensities of manufacturers and their desires for a level playing field -- and again being practical -- I believe the regulatory route presents the shortest, and perhaps fastest, path to a solution.  Going it alone as suggested by DL8OV, while altruistic and commendable, raises the question how and by what avenues?  Given the independence of thought by the amateur community at large, that could turn out to be like herding cats.

At this point I'm encouraged by all the good thought and ideas expressed in this thread.  I believe we are gradually converging on some kind of consensus.

Best to all,
Stu, K5PB


I couldn't agree more Stu as I have been saying that from the beginning of the thread although I could not have said more eloquently than your post. Honestly if I were a manufacturer and there was nothing forcing me to change, my thoughts would be why would I spend  R&D money to improve on a spec that I already meet? If the FCC spec changes, I bet the Yeacomwoods of the world would have engineers designing new PA's for their rigs tomorrow for fear of being locked out of the largest amateur radio market in the world. Money talks and "you know what" walks.....


Title: RE: Ham Xcvrs' and Amps', Transmit Spectral Purity, IMD Products, vs. comm/maritime
Post by: G3RZP on September 29, 2014, 02:16:15 PM
OK gentlemen,

can you answer these questions?

1. How often does Joe Q Average ham buy a new rig?

(Hint: in my case, I'm still using the now much modified FT102 my father bought in 1983, so I guess I am not typical)

2. How long does it take for a rig to end up as landfill? How many FT101s are still around?

Other than having a new rig for the sake of it, rather than having a new rig for extra performance or facilities, why does a ham with an existing working rig change?

So how long will it take for any improvement to work its way through the system?

Long after I am an SK, I bet.


Title: RE: Ham Xcvrs' and Amps', Transmit Spectral Purity, IMD Products, vs. comm/maritime
Post by: K5PB on September 29, 2014, 02:47:53 PM
Peter, I agree that it probably will take a while for improvements to work all the way through the system, but I think that's a tangential argument.  If we don't begin now, when???  Yes, we may all be SK by then, but think of it as a legacy to those who follow.


Aside to W3RSW: Good points, but it was your last few lines that me rolling on the floor.  ;D  You, sir, are not only a philosopher but a keen observer of the human condition. Still LOL

All the best,
Stu, K5PB


Title: RE: Ham Xcvrs' and Amps', Transmit Spectral Purity, IMD Products, vs. comm/maritime
Post by: K2GWK on September 29, 2014, 04:01:56 PM

So how long will it take for any improvement to work its way through the system?


In the case of IMD performance, unless there is motivation for a manufacturer to change, never.......


Title: RE: Ham Xcvrs' and Amps', Transmit Spectral Purity, IMD Products, vs. comm/maritime
Post by: K5PB on September 29, 2014, 05:44:10 PM
Guy K2GWK, thanks for the kind words.  Much appreciated.

Stu, K5PB


Title: RE: Ham Xcvrs' and Amps', Transmit Spectral Purity, IMD Products, vs. comm/maritime
Post by: KA4WJA on December 24, 2014, 08:13:47 PM
With all the recent discussion of "amps for qrp rigs" and "solid-state vs. tube", etc. and the IMD products, etc., I though some may want to have a look at some of this again?

Or maybe not?

Happy Holidays!

73,
John,  KA4WJA



Title: RE: Ham Xcvrs' and Amps', Transmit Spectral Purity, IMD Products, vs. comm/maritime
Post by: KA4WJA on January 08, 2015, 05:37:47 PM
Mike,
Yeah, this is a "yikes" moment for many....unfortunately, including many K3 owners...
This is a scan of a K3, by Rob Sherwood, NC0B, running at 100 watts PEP, from 2008 / 2009....and he even commented that this was not something that a "firmware upgrade" can help...

Scott, please have a look at the spectral scans of some modern, current production transceivers (and some older and/or maritime/commercial, ones too), rather than trying to just use the 3rd order spec....
The IMD3 spec might be what so many wish to quote/compare, but when you actually look at the scans, you will quickly see why many ARE concerned about this!!

Just look at the K3....would you want to operate within 5khz - 10 kHz of this???  Not to mention, what happens when a whole group of K3's, etc show up on-the-air (contest, etc.)???
(http://i57.tinypic.com/1zlzq80.jpg)

 WOW! THAT's an Elecraft K3???!!! You just put my plans --for my next rig to be a K3-- on hold.

Is that from the latest production run? I did hear they had issues with bad-sounding SSB, but I though that was ironed out. I don't know, but I would like to.

Thanks for posting this!  :)


I hope this helps some of you out...


73,
John,  KA4WJA


Title: RE: Ham Xcvrs' and Amps', Transmit Spectral Purity, IMD Products, vs. comm/maritime
Post by: KA4WJA on January 08, 2015, 07:43:42 PM
FYI, I should have pointed out that the ARRL 2-tome IMD specs  / test results of  amplifiers, are done using two separate discrete input signals (from two signal gens, or two CW carriers from two different exciters/transmitters/transceivers), and are therefore the exact 2-tome IMD figures for just the amplifier(s), and do NOT include any IMD contribution from the exciter/transmitter/transceiver....

BUT...

But, the 2-tone IMD test of the FT-1000 MkV and Alpha 77 (8877), the green spectral scan above, is done with driving the amp / 8877 with the FT-1000 MkV (in Class A), and therefore shows the total IMD of both the exciter and the amplifier....which is worse than what you'd see when testing it in the "normal" way (using two separate, discrete, signals into the amp)....


Sorry, if that caused any confusion....
Just wanted to make sure that everyone understood that.... :)



73, 
John,  KA4WJA


Title: RE: Ham Xcvrs' and Amps', Transmit Spectral Purity, IMD Products, vs. comm/maritime
Post by: W1BR on January 08, 2015, 08:32:01 PM
I think W8JI has shown evidence that is possible to reach erroneous conclusions that show better IMD than is actually generated when operating dynamically on the air (SSB vs. steady state two-tone tests.) Tom has also suggested using a three tone test, which is far more demanding, adds the dynamics resulting from ALC action.

Pete k1zjh


Title: RE: Ham Xcvrs' and Amps', Transmit Spectral Purity, IMD Products, vs. comm/maritime
Post by: KA4WJA on January 08, 2015, 09:17:41 PM
Pete,
Yes, I agree....
3-tone testing, white noise testing are better, than 2-tone testing....as is dynamic testing....(I'm a longtime proponent of 3-tone testing)


But, what we have now is a database of 2-tone test results, as well as specific regs that use 2-tone tests....

So until things change, we have this....
We can use the info we have, including actually looking at the spectral scans and not just reading a 3rd order figure off a page....and try to evaluate the respective radios on-the-air now and what we may desire to use on the air...
And, ask the ARRL and others to do different testing...



BTW, as I wrote, I'm a longtime fan of 3-tone testing....going back decades....as this was the standard used to spec-out many NTSC-video transmitters / amps (the ones that didn't separately combine the FM audio transmitter), as you have the picture carrier, color-burst carrier and audio carrier....as well as analog NTSC CATV components...


73,

John,  KA4WJA


Title: RE: Ham Xcvrs' and Amps', Transmit Spectral Purity, IMD Products, vs. comm/maritime
Post by: W3RSW on January 11, 2015, 10:47:26 AM
I think 3 tone would be instructive, but perhaps a little harder for accurate calibration of the amplitudes of three tones in a typical ham Rig's test oscillator.  At least Elecraft provides a two tone osc. for testing purposes in the K3, ( easier to get a 2 equal tone oscillator circuit and calibration control done economically as a throw-in.)

Then:
Quote
Just look at the K3....would you want to operate within 5khz - 10 kHz of this???  Not to mention, what happens when a whole group of K3's, etc show up on-the-air (contest, etc.)Huh

Well we can see by the K3's 40kHz spectral graph illustrated that products 5 to 10 kHz out are 50db down Left, 55 +/- db  down right at 5kHz, and greater than 60db down both left and right both sides at 10kHz.  As has been mentioned at least once in this long thread, 50Db down from 100 w PEP is 50dbm - 50db or 0dbm, a fantastically huge 1 milliwatt, QRPp for fun and profit.  ;D   At the graph's +/- 20kHz limits, products are about 80db down or -30dbm or 0.001milliwatts.   A Killa in Manila for your regen.

One really needs to remember that 0.001 milliwatts is not tied directly to the 50 ohm  input of your receiver but is radiated from elsewhere and is further diluted as inverse square radiation from a point, granted sometimes magically "enhanced" more than expected by ionosphere, refraction, reflection, ground waves and all possible combinations of other quirky real world conditions.  In most combinations it is undetectable; sometimes the 100 watt signal is barely detectable for that matter.

And to mention what if a "whole group" of K3's show up on the air in a contest, that's a stretch of superposition theorem for the combined noise floor, let alone economics theory calculating the odds of the majority of contesters using K3's.  That'll be the day...

Thinking in order of magnitudes helps arguments as well as calculations.

Not that I disagree that the majority of manufactured amplifiers of all levels need cleaner IMD specs.  I also think that can be done reasonably economically on a discrete parts basis, but that boards, power supplies, design, literature (best spin on the "error of our ways" since vac. tube finals) and SIM redesigns are the chief holdups.

Of course you shouldn't want to further amplify (QRO) a dirty signal so that's an additional reason for holding down IM, etc. in early and preamp stages, finals in 100 watt radios and additional linear amplifiers.

Don't worry, SDR's with pre-distortion correction are leading the way.  Pressure is mounting on all the manufacturers.  As in the voting populace, the choice is ours if we
choose to make it so as a majority.  The market will be the 'decider'. You really don't want regulation if at all possible.



Title: RE: Ham Xcvrs' and Amps', Transmit Spectral Purity, IMD Products, vs. comm/maritime
Post by: KA4WJA on January 11, 2015, 01:17:44 PM
Rich,
I get your point here....
(but, at the ends of the plot (+/- 20khz) the IMD products are not quite 80db down...)
 
Quote from: W3RSW link=topic=97093.msg813247#msg813247
date=1421002046
Then:
Quote
Just look at the K3....would you want to operate within 5khz - 10 kHz of this???  Not to mention, what happens when a whole group of K3's, etc show up on-the-air (contest, etc.)Huh

Well we can see by the K3's 40kHz spectral graph illustrated that products 5 to 10 kHz out are 50db down Left, 55 +/- db  down right at 5kHz, and greater than 60db down both left and right both sides at 10kHz.  As has been mentioned at least once in this long thread, 50Db down from 100 w PEP is 50dbm - 50db or 0dbm, a fantastically huge 1 milliwatt, QRPp for fun and profit.  ;D   At the graph's +/- 20kHz limits, products are about 80db down or -30dbm or 0.001milliwatts.   A Killa in Manila for your regen.

One really needs to remember that 0.001 milliwatts is not tied directly to the 50 ohm  input of your receiver but is radiated from elsewhere and is further diluted as inverse square radiation from a point, granted sometimes magically "enhanced" more than expected by ionosphere, refraction, reflection, ground waves and all possible combinations of other quirky real world conditions.  In most combinations it is undetectable; sometimes the 100 watt signal is barely detectable for that matter.
But, I stand behind my original words....as I would NOT want to operate with 5khz to 10khz of the K3....even with its products down 50db - 55db at those freq separations, that can mean my effective noise floor is now the level of the distortion products on the guy using the K3, 5-10khz away....
So, if I was trying to work a guy with a signal of say S-6, and the guy on the K3 was S-9 plus 40, I'm out-of-luck.....but what if he was just S-9 plus 10, thenI'd be okay to work a weak signal down to S-2 or so....

And, while I stand by my words, I DO understand that this is most noticeable when trying to work a weak station in amongst strong stations....
And, ironically, this is the exact selling point of receivers in all the multi-thousand dollar rigs (like the K3), to be able to work the weak signals in amongst the strong ones, yet these same manufactures sell these rigs with such crappy transmitters that there is little chance to fully utilize their great receivers, if there are others using their rigs on-the-air!!

Besides, my original point here last year, was that there ARE rigs made that DO have excellent transmit spectral purity, and they do not cost thousands.... :)


 

I'm not a big contester (FD, and a VHF contest / 160m contest, once-in-a-great-while), and I do recognize the "mic gain" and "all knobs to the right", are today the primary problems during contests (as well as overdriven amps), but with more and more rigs with poor transmit spectral purity, having been sold in the past 10 - 20 years, fact is things are worse now that 30+ years ago (higher noise floors, from combinations of all the other transmitters), and if more and more use even worse transmitters, things will get even worse!!!

Quote from: W3RSW link=topic=97093.msg813247#msg813247
date=1421002046

And to mention what if a "whole group" of K3's show up on the air in a contest, that's a stretch of superposition theorem for the combined noise floor, let alone economics theory calculating the odds of the majority of contesters using K3's.  That'll be the day...
So, while my words might have a touch of hyperbole....and I do NOT wish to single-out the K3 (sorry about that!)....the facts are, that more rigs with poor transmit spectral purity on-the-air DOES cause problems and it if you add even more poor rigs, things WILL get worse....
So, without hyperbole and without singling-out the K3, I stand behind my words...





And here, I do agree with you (mostly...)
Quote from: W3RSW link=topic=97093.msg813247#msg813247
date=1421002046
Of course you shouldn't want to further amplify (QRO) a dirty signal so that's an additional reason for holding down IM, etc. in early and preamp stages, finals in 100 watt radios and additional linear amplifiers.

Don't worry, SDR's with pre-distortion correction are leading the way.  Pressure is mounting on all the manufacturers.  As in the voting populace, the choice is ours if we
choose to make it so as a majority.  The market will be the 'decider'. You really don't want regulation if at all possible.
I'm all for the market deciding....
I just wish more hams would pay a little bit more attention to their transmit signal (after all that is all we each really have control over), rather than worrying about the last db or rec dynamic range for 2khz/close-in spacing....
(and if you listen to Rob Sherwood's presentations, he's been touting this for a decade now....some may think it ironic, as it is his "receiver list" that has been the talk of the airwaves for the past 10+ years, but he has also been trying to remind all of us that these great rec specs are becoming meaningless on-the-air due to the plethora of poor transmitters....)


All my best....

73,
John,  KA4WJA


Title: RE: Ham Xcvrs' and Amps', Transmit Spectral Purity, IMD Products, vs. comm/maritime
Post by: W3RSW on January 11, 2015, 01:32:38 PM
left side nominally 80 db down from pep , top of graph, -a phantom point.
-- two tones are already 6db down.
(EDIT: oh, it's truncated. Would you believe 75db on right side?) ;D

In real time, signals jump around a bit. The spectra are average over a period of time of course.

And another 10db down at 5kc out, representative of some of the better rigs is now 0.1mw.
Happier with that?  Place that point on your grosser S-meter scale for illumination.  ;D
- a little over another S unit.

yeah, somewhat sorry for repeating a lot of what's already on this thread, most already said by others.

now I'll read your post more thoroughly.  Seems we already agree on most except the shock factor. "Absolutes" need to be substantiated by some calculation, particularly a composite noise floor affected by adjacent signals (out of passband, of course) of a reasonably filtered transmitted and received signal.


Title: RE: Ham Xcvrs' and Amps', Transmit Spectral Purity, IMD Products, vs. comm/maritime
Post by: KA4WJA on February 10, 2018, 05:56:02 PM
Hello to all,

I suppose that since most never hear themselves on-the-air, and darn few ever hear what their own transmitter does on freqs +/- a few khz (or worse +/- 10 to 20khz), the actual transmit IMD and spectral purity of our signals tend to get over-looked...and that is a shame!

But, the simple fact is that the limiting factors in most of our HF receivers these days are:

a)  The transmit products (IMD for SSB and digital modes and wide-band noise/transmitter phase-noise, primarily effecting CW) of all the other stations on-the-air....

b)  Local noise levels / RFI (caused by all the misc RF radiating products around us these days)

The limiting factors are NOT how good the 3rd-order IMD spec is on your receiver...although in some very rare instances (probably < 0.1% of hams), this can be a factor, but even then not the only one...

I hope this info here helps some of my fellow hams understand what our modern HF rigs are doing to pollute the airwaves, even if they're operated with "good amateur practice", in accordance with the factory operations manual, etc...(now, if you crank-up the mic gain on most rigs, things will get worse....and many times, they'll get really bad....but, if you start with a bad rig, things get really bad very quickly...and if you start with a good rig, things might be "okay")


Almost 4 years since I started this thread, and after three years of inactivity, I'm sure there will be one or two hams here that will not appreciate bringing this thread back to life....but, there are a few reasons that I'm doing this.


1)  The basic reasons are:

a)  Tornado spawned by Hurricane Irma took down two of my 3 large trees (and a few smaller ones) and all my wire antennas supported there, as well as destroyed my rotor and damaged antennas on my tower (but I do have a new tower on the ground)...so I'm considering a station rebuild and was thinking about buying a new rig as well....

Updating my research....and then during some recent discussions with friends about transmit IMD, I found them repeating the oft-heard mantra of "high-voltage SSPA's have clean transmit signals", but here (like many things in life) this myth just persists.  :(


b)  New radios on the market, many of them costing 1000's of $$$$, and only the Apache Labs (ANAN) software pre-distortion equipped SDR transceivers have significantly improved transmit IMD.  (sad, but true!)


c)  A clarification of sorts showing that 2-tone testing is actually very representative...and that white noise testing can make explaining results easier to laypersons, as the effects are easier to show on the analyzer screen, using white noise....(although, dynamic testing can show deficiencies of power supplies, etc. that static two-tone testing / white noise testing do not show, 2-tone testing DOES show what is happening!  and 3-tone tests from VHF/UHF TV-broadcast amplifiers that I've looked at years ago, also correlated well to 2-tone testing...)

From one of Rob Sherwood's papers, here is a 2-tone test overlaid with a white noise test (of his Icom IC-781)...
Have a look:
(http://i67.tinypic.com/2hdsnde.jpg)


{BTW, during my discussions with friends, one asked why I didn't just post all the IMD specs of all the rigs???  Well, that's a LOT of data to sort thru, and I don't have the time for that...but then thought, I could do so (like I did for HF Amps) for at least a dozen or so rigs....Which ones??  I took suggestions, and also had some in mind that I might want to buy.}

For IMD comparisons of HF Amps, have a look here:
https://www.eham.net/ehamforum/smf/index.php/topic,100600.0.html


2)  Those that just want the brief nitty-gritty...here 'ya go:

a)  Even now in 2018, there is still no direct correlation that "12 volt PA's splatter, and hi-voltage PA's are clean"....yes, some hi-voltage PA rigs produce better IMD figures than some 12 volt PA rigs, but it is not a direct correlation...


b)  With the exception of the "pre-distortion" enabled Apache Labs ANAN rigs, the Icom M-802 HF Marine/Ham Transceiver still produces better IMD figures (by a significant amount) than ALL current HF ham rigs (or any made in the past 40+ years), and the Icom is a 12vdc rig, using a simple 12vdc PA!

http://www.eham.net/reviews/detail/6205

But, some minor improvements from Kenwood with their TS-590SG (at ~ $ 1400 USD) and for those with hefty wallets their TS-990S (at ~ $7000 USD), and those who want to take out a second mortgage to buy a rig might look at the IC7851 (at ~ $14,000 USD!!!)...these might allow some like me looking for "a real radio with knobs" to at least not pollute the airwaves too much....BUT..

I still wonder why Icom (and others) just won't make a decent transmitter and PA...heck the Icom M-802 sells for ~ $1800....but it appears that most hams are really getting shafted with crappy transmitters!


c)  This discussion is about transmit IMD and spectral purity, not about receivers....but many seem to be picking rigs based on their position on a list (assuming they can afford them)...I'm still surprised by the focus on "Sherwood's List"....now Rob Sherwood is a GREAT guy!!  A GREAT ham!  And, has done wonders for my favorite brand of HF radio, R.L. Drake!!  I love the guy! :) :)

But, geeze guys...."the list" isn't the "be all / end all" of how to judge HF rigs....and if you don't believe me, just read what Rob himself writes!!  Please remember that these "85 to 90db radios" are specified for serious CW operations/pileups/contesting...and for SSB operations, even in pileups and SSB contesting, receivers with 15 to 20db worse close-spaced IMD specs are adequate, and these other factors (mentioned in the quotes below) are important!

(http://i66.tinypic.com/15gz0cj.png)

Quotes from Rob [I added some bold type for emphasis]:
{What level of performance do we need close-in on CW for a radio to perform well most of the time? I think 85 dB will suffice most of the time. Certainly one may want a 100 dB dynamic range radio, but other factors of a transceiver’s performance are very important, too. Ten-Tec receive audio is better (cleaner) than Elecraft K3 audio, for instance.

On SSB transmitted intermodulation products from QRM 3 to 5 kHz away is usually far above the LO phase noise (RMDR) of today’s top receivers.

Thus the “holy grail” of wanting a 100 dB radio is only a CW pile-up issue.

If every other feature or specification of a radio was top notch, it would seem logical to pick a 100 dB radio over an 85 or 90 dB radio, however this is rarely the case. With good firmware, Ten-Tec and Elecraft have made their DSP radios much less susceptible to having the AGC “load up” or “over react” to impulse noise (clicks, tick and pops). No Japan, Inc. radio at the moment has figured this out.........

How a ham picks one transceiver over another is likely all over the map. For me if the ergonomics are poor, or if the receive audio is fatiguing to listen to, then that radio falls off my selection list. At the end of the day, hopefully whatever we buy we enjoy using.
I sold an expensive radio about 10 years ago that worked OK, but I just didn’t like it compared to my 15 year old radio of the same brand.
73, Rob, NC0B
(15-JUL-2014) }

{ DO NOT OVER-RATE DYNAMIC RANGE
One thing that I need to stress is [that] the amateur community has become obsessed with which radio has a close-in dynamic range a few dB higher than another.

Decades ago Tom Rauch W8JI and I were saying that a close-in dynamic range (DR3) of 80 dB would perform well most of the time. Back then with all the up-conversion radios on the market, most had a DR3 around 70, with some in the 60s.
The Orion I was the first commercial radio to go back to what we now call "down conversion" and it had a DR3 over 90 dB. The amateur community now has a good selection of radios that have a DR3 value in excess of 85 dB.

It is rare that an 85 dB radio will not be adequate in a CW pileup. [and from other papers/talks:  a ~ "70db radio" works well, in SSB service/pileups/contesting.]

All the T-T products except the Omni-VII are 90 dB or better, along with products from most of the other OEMs.
Once you have decided you want a 90 or better radio, for example, then there are lots of other important parameters to consider, such as:
• clean receive audio for low fatigue in a contest,
• a good AGC (which T-T has recently improved in respect to handling impulse noise),
• the ease of use (user interface),
• reliability,
• quality of service and long-term parts support,
• long term firmware support,
• lack of ALC overshoot, (a problem with the TS-590S and IC-7410 for example) when driving a linear.
• The list goes on.
You don't buy a car with one specification, like horse power. The 427 cubic inch Corvette from years ago had lots of horse power but didn't handle very well!
73, Rob, NC0B
(16-DEC-2013) }

{ THE BIG PICTURE:
With 10 or more radios with 85 to 105 dB DR3s at 2 kHz, it is time to look at the big picture:
 Clean receive audio,
clean transmitter IMD,
 a good AGC that doesn’t go nuts over an impulse click, tick or pop,
 a reliable radio that doesn’t beak all the time,
an ALC that doesn’t overshoot and fault your linear amplifier, or even worse blow your amp.
 And when service is needed, good and reasonably fast factory service.
 How about long term support of radios out of production, such as on-going firmware updates and parts availability. (Unfortunately there is only so much anOEM can do about supplying out-of-production chips, PA transistors, LCD screens, etc.)


At the end of the day, do you enjoy using your radio on the air?

I hate to tell you how many radios I have had the good fortune to borrow and use on the air in contests that I really would not want to have to use on a daily basis. I sold one very expensive radio that just wasn’t a good fit for me. I took the money and put up two more towers and Yagi antennas.
Hopefully when you turn off your rig after a contest, a DX contact or just a rag chew, you feel that “that was fun”. This is a hobby, and using your radio should be enjoyable.
73, Rob, NC0B
(21-DEC-2013) }



3)  Okay... Now, let's look at some modern rigs....and some of my favorites...

These are 3rd, 5th, 7th and 9th order transmit IMD figures, in db below PEP, with the rigs operated at the spec'd max output (typically 100 watts) unless otherwise noted.

{FYI, unless otherwise specifically notated, all of these Transmit 2-tone IMD test figures are from published ARRL Product Review Tests...in some circumstances they found an "outlier" (worst band) and also listed "typical" as well as this "worst case", and in those cases, this data is also included...(also note that some rigs may only have old spectral scans and/or data listed for 3rd and 5th order IMD, but every effort is made to provide as much real data as I can.) }


[Please note the asterisks, etc....as these are ones I have personally owned (***), have used extensively(**), used briefly and liked(*).....and/or interested in(+)....also please note I use italics to highlight comment/opinion, everything else is factual data.]


+  Apache Labs  ANAN-8000D [no ARRL test yet, so these figures are from Adam Farson, VA7OJ/AB4OJ, from Sept 2017]  (50vdc LDMOS PA)

33 / 40 / 54 / 60  (with NO pre-distortion) at 200 watts

67 / 70 / 70 / 70  (with pre-distortion) at 200 watts

Sorry, I cannot copy the analyzer spectrum scan of the ANAN-8000D, as this is proprietary data of Adam's....but you can have a look for yourself on page #33  of this page
http://www.ab4oj.com/sdr/apache/anan8000dle_notes.pdf




+  Apache Labs ANAN-100D  (12vdc PA)

29 / 35 / 39 / 44 (worst case,  NO pre-distortion)

38 / 38 / 44 / 52 (typical, NO pre-distortion)

49 / 56 / 59 / 60  (worst case, with pre-distortion)

52 / 54 / 60+ / 60+  (typical, with pre-distortion)



*** Icom M-802  (12vdc PA) {nice HF marine and ham rig...few "user" adjustments, but a real nice rig w/ GREAT transmit IMD!}

47 / 50 / 58 / 60  (at 150 watts)  {3 to 6db better at 100 watts}

Have a look:

(http://i67.tinypic.com/30u6cfd.jpg)



*** Drake TR-7  (12vdc PA)  {although not the cleanest IMD, one of my favorite rigs of all time, sweet SSB audio xmt and rx, and no modern ALC issues....one of the best SSB receivers (and darn good CW as well) in a ham rig, ever!}

38 / 44 / 51 / 58 (at 100 watts)

33 / 38 / 45 / 50 (at factory spec'd 150 watts)


** Kenwood TS-830s  (vacuum tube PA, two 6146's) {sweet rig all-around, my 2nd favorite}

32 / 52 / 70 / 70+


Collins 32S-3  (vacuum tube PA, two 6146's)

42 / 53 / 65 / 76

Have a look:
(http://i68.tinypic.com/27z984y.png)



** Icom IC-781  (28vdc PA) 150-watt out {not the cleanest IMD, but a great SSB rig, both xmt and rx}

37 / 39 / 47 / 50 (old ARRL test) at 150 watts out

35 / 43 / 49 / 54 (from Rob Sherwood's paper)

Have a look:
(http://i67.tinypic.com/2hdsnde.jpg[img]FT-1000MP MkV  (30vdc PA) {keep ALC to zero, and this is fine Class A xmtr}27 / 48 / 52 / 50  in Class B45 / 64 / 72 / 80  in Class A  (ARRL test)48 / 74 / 82 / 86  in Class A  (from Rob Sherwood's paper)Have a look:[img]http://i63.tinypic.com/20rmfbp.jpg)



* Yaesu FT-102  (vacuum tube PA / three 6146b's)

40 / 40 / 50 / 60  (at 150 watts out)


** Icom IC-765  (12vdc PA)  {a great rig in it's day, and darn good even by 2018's standards...used the 765 and 761 for many hours each day for months on end, 6 - 7 days/wk, at MARS station in 1990/91...}

40 / 45 / 48 / 50


** Icom IC-761  (12vdc PA)  {a great rig in it's day, and darn good even by 2018's standards...used the 765 and 761 for many hours each day for months on end, 6 - 7 days/wk, at MARS station in 1990/91..}

31 / 45 / 48 / 50


* Icom IC-756ProII  (12vdc PA)

30 / 40 / 48 / 50


+  Kenwood TS-590SG  (12vdc PA)

31 / 38 / 48 / 55 (worst case)

42 / 38 / 48 / 58 (typical)


+  Kenwood TS-990  (50vdc PA)

31 / 46 / 52 / 57  (worst case)

39 / 46 / 54 / 56  (typical)

The rigs above are ones that I've used / been interested in...
Note the asterisks above, as these are ones I have personally owned (***), have used extensively(**), used briefly and liked(*).....and/or interested in(+)


The rest below were all suggested by some friends...and/or prominently discussed by many hams.


Elecraft K3  (12vdc PA)

33 / 40 / 48 / 50

Have a look:
(http://i64.tinypic.com/2daa77m.jpg)


Elecraft K3s  (12vdc PA)

30 / 38 / 41 / 48  (typical)

35 / 36 / 48 / 62 (specially tuned transmitter and PA, by Elecraft engineering dept, after the above disappointing results were reported, prior to publication, see Nov 2016, QST, page 50, for details)



Icom IC-7300  (12vdc PA)

30 / 37 / 44 / 58


Icom IC-7851  (50vdc PA)

29 / 40 / 48 / 70  (worst case)

36 / 52 / 49 / 61  (typical)


Icom IC-7800  (50vdc PA)

32 / 49 / 52 / 52


Icom IC-7600  (12vdc PA)

31 / 35 / 41 / 48


Hilberling PT-8000A  (50vdc PA)

29 / 41 / 50 / 52  (worse case)

35 / 48 / 54 / 59  (typical)


Icom IC-706  (12vdc PA)

33 / 31 / 38 / 44


Icom IC-706mkIIG  (12vdc PA)

30 / 33 / 37 / 43


Yaesu FT-857  (12vdc PA)  {from Aug '03 QST}

25 / 40 / 50 / 52

Yaesu FT-857D  (12vdc PA)  {from Nov '04 QST}

21 / 32  (3rd and 5th order IMD was all that was reported)


Yaesu FT-897  (12vdc PA)

23 / 37 / 47 / 50


Icom IC-735  (12vdc PA)

33 / 39 / 43 / 47


Yaesu FTdx-5000  (50-vdc PA)

30 / 48 / 46 / 47  (class B)

43 / 64 / 68 / 72  (class A)  [but, you must NOT have any ALC, just like the older FT-1000MP MkV, otherwise you're almost defeating the advantage of Class A operation]

Have a look at how the ALC screws things up, zero ALC vs. half-scale ALC:
(http://i63.tinypic.com/svjc0m.png)


Yaesu FT-dx-3000  (12vdc PA)

27 / 40 / 42 / 52  (worse case)

31 / 40 / 45 / 52  (typical)


Yaesu FT-991  (12vdc PA)

22 / 32 / 39 / 45  (worse case)

26 / 37 / 41 / 46  (typical)


Yaesu FTdx-1200  (12vdc PA)

32 / 35 / 42 / 50  (worse case)

37 / 38 / 44 / 50  (typical)


Kenwood TS-590S  (12vdc PA)  (un-modified units suffer from serious ALC-overshoot and other ALC issues)

29 / 32 / 42 / 52


Flex-5000  (12vdc PA)

34 / 40 / 48 / 54


Flex-6500  (12vdc PA)

32 / 43 / 48 / 51  (worse case)

39 / 42 / 49 / 55  (typical)


Flex-6700  (12vdc PA)

32 / 40 / 44 / 55


Ten Tec Orion  (12vdc PA)

32 / 42 / 52 / 58


Ten Tec Orion II  (12vdc PA)

28 / 42 / 44 / 52


Ten Tec Omin VI+  (12vdc PA)

26 / 43 / 45 / 54


And, a few 10-watt QRP rigs:

Elecraft K2  (12vdc PA) 10-watt QRP

29 / 40 / 50 / 62


Elecraft  KX3  (12vdc PA) 10-watt QRP

30 / 40 / 51 / 55


Ten Tec Argonaut (12vdc PA)  10-watt QRP

30 / 36 / 47 / 51  (worse case)

37 / 42 / 58 / 59  (typical)


Flex-1500  (12vdc PA)  10-watt QRP

22 / 38 / 48 / 48


I hope this helps some understand what our modern HF rigs are doing to pollute the airwaves, even if they're operated with "good amateur practice", in accordance with the factory operations manual, etc...(now, if you crank-up the mic gain on most rigs, things will get worse....and many times, they'll get really bad....but, if you start with a bad rig, it's bad no matter what and things get really bad very quickly...and if you start with a good rig, things are better from the start and might be "okay")


The 40-odd radios above represent most of the popular HF rigs on the ham bands today and sold in the past 30 - 40 years, as well as a few that are very new (and some so obscenely expensive that few hams will ever operate one)....oh, and 25 of the above 40 rigs, also find themselves in the top 30 of the rigs listed by "narrow-spaced (2khz) 3rd-order rec IMD" on Rob Sherwood's list, maybe now some will see the red herring that buying a rig from a "list" can be? :)


73,

John,  KA4WJA



Title: RE: Ham Xcvrs' and Amps', Transmit Spectral Purity, IMD Products, vs. comm/maritime
Post by: KA4WJA on February 10, 2018, 07:09:49 PM
I wanted to edit/clarify something above, but unable to do so after 30 minutes???  So, here's a very brief post. ")

In case you want to look specifically at this "12vdc PA myth", please have a look:


1)  The TS-590SG and TS-990S are the same brand, made in the same factory, of similar vintage, etc....and if you compare their respected transmit IMD, the "50vdc PA" is not the panacea the myth states. :)

Kenwood TS-590SG  (12vdc PA)  31 / 38 / 48 / 55 (worst case)
                                                       42 / 38 / 48 / 58 (typical)

Kenwood TS-990  (50vdc PA)      31 / 46 / 52 / 57  (worst case)
                                                     39 / 46 / 54 / 56  (typical)

[Remember the > $7000 cost of 990S is FIVE times the price of the 590SG of ~ $1400]



2)  And, what about Icom?

Well, the IC-7300, IC-7800, and IC-7851, are the same brand, made in the same factory, of similar vintage, etc....and if you compare their respected transmit IMD, here again the "50vdc PA" is not the panacea the myth states. :)

Icom IC-7300  (12vdc PA)   30 / 37 / 44 / 58

Icom IC-7851  (50vdc PA)   29 / 40 / 48 / 70  (worst case)
                                            36 / 52 / 49 / 61  (typical)

Icom IC-7800  (50vdc PA)   32 / 49 / 52 / 52

Of course there is also the Icom M-802.

Icom M-802  (12vdc PA)    47 / 50 / 58 / 60  (at 150 watts)  {3 to 6db better at 100 watts}

[The price of the 7300 (~ $1300) is ONE TENTH the cost of the 7851 (~ $12,500)...with the M-802 at ~ $1850...]



3)  Unfortunately, Yaesu hasn't had many rigs with even "acceptable" transmit IMD, unless run them in Class A (and without any ALC), and of course they aren't cheap radios...



73,

John,  KA4WJA



Title: RE: Ham Xcvrs' and Amps', Transmit Spectral Purity, IMD Products, vs. comm/maritime
Post by: KB2TIS on February 11, 2018, 09:21:42 AM
> Icom M-802  (12vdc PA)    47 / 50 / 58 / 60  (at 150 watts)  {3 to 6db better at 100 watts}

Has anyone actually measured these kind of values in real life, not just what is claimed in a filing somewhere?

https://www.eham.net/ehamforum/smf/index.php/topic,100634.msg815777.html#msg815777

Seems to show that those numbers are a dream even at 100W.


Title: RE: Ham Xcvrs' and Amps', Transmit Spectral Purity, IMD Products, vs. comm/maritime
Post by: KM1H on February 11, 2018, 09:44:39 AM
Well, since you just had to resurrect this antique thread while also starting a new one to add to the confusion here are a few of my comments.

1. Limit ALL ham rigs to no more than 5-6dB of compression/limiting, no more than rated output (which includes internal power controls), and restrict the maximum amount of the audio gain by software sampling the RF output level.
Minimal added engineering required and even opened up still acceptable specs/performance on marine and other commercial channels.

2. White noise IMD testing goes back over 50 years from my own personal experience with military products and their acceptance testing including HF amps in the 1-10KW range....using tetrodes.

Quote
Kenwood TS-590SG  (12vdc PA)  31 / 38 / 48 / 55 (worst case)

Please specify the testing method; those look like ARRL cherry picked Watts to me and not what any respectable marine or military multi channel amp would accept.
                                                     

Carl


Title: RE: Ham Xcvrs' and Amps', Transmit Spectral Purity, IMD Products, vs. comm/maritime
Post by: KA4WJA on February 11, 2018, 05:39:43 PM
Carl,
Sorry about the misspelling.  :)


1)  As for what the testing method is....and "cherry picked watts"??
First allow me to include all the TS-590SG data, from yesterday:
Kenwood TS-590SG  (12vdc PA)  31 / 38 / 48 / 55 (worst case)
                                                       42 / 38 / 48 / 58 (typical)
Quote
Kenwood TS-590SG  (12vdc PA)  31 / 38 / 48 / 55 (worst case)

Please specify the testing method; those look like ARRL cherry picked Watts to me and not what any respectable marine or military multi channel amp would accept.

2)  Now, as to what the testing method is...
As I wrote above, these are the published ARRL Product Test results, as printed in QST magazine...(in the case of the TS-590SG, that you partially quoted, you'll find them on page 49, of July 2015 issue)

Here is what I wrote yesterday:
These are 3rd, 5th, 7th and 9th order transmit IMD figures, in db below PEP, with the rigs operated at the spec'd max output (typically 100 watts) unless otherwise noted.

{FYI, unless otherwise specifically notated, all of these Transmit 2-tone IMD test figures are from published ARRL Product Review Tests...in some circumstances they found an "outlier" (worst band) and also listed "typical" as well as this "worst case", and in those cases, this data is also included...(also note that some rigs may only have old spectral scans and/or data listed for 3rd and 5th order IMD, but every effort is made to provide as much real data as I can.) }

For the detailed test procedure, I thought we covered this a couple years ago, but here 'ya go.

The ARRL product test product test procedures are all detailed here:

http://www.arrl.org/test-procedures-manual

If you look at pages 17 thru 19, you will see the details of the two-tone IMD test procedures.


Here they are (without the diagram):

Quote
4.5 TWO-TONE TRANSMIT IMD TEST

4.5.1 The purpose of the Two-Tone Transmit Test is to measure the intermodulation-distortion (IMD) products present in the RF output of the DUT transmitter. The transmitter will be operated in the SSB mode at 3.900 MHz and14.250 MHz initially and then on all other available bands subsequently. A two-tone audio input at frequencies of 700 and 1900 Hz, within the manufacturer's amplitude specifications, will be used.


4.5.2 Test hook-up (See Fig. 4-5)
  

        NOTE: If proceeding in the test series, only the two-tone generator, shown within the dotted      line, must be added to the previous Spectral Purity Test hook-up for the IMD Test.


    4.5.2.1 With all power switches in the OFF position and the transceiver in the receive mode,             connect the following:

Connection                                             Connectors                               Cable Type
DUT RF OUT To Wattmeter IN           As Required To Type N             50-Ohm Coax
Wattmeter OUT To PWR Attn IN        Type N To Type N                      50-Ohm Coax
PWR Attn OUT To Step Attn              Type N To BNC                          50-Ohm Coax

Connection                                                  Connectors                               Cable Type
Step Attn OUT To Spectrum Analyzer IN     BNC To BNC                       50 Ohm Coax
--------------------------------------------------------------------------------------------------------------------------
Two-Tone Generator OUT To DUT MIC IN    BNC To As Required                  Coax
--------------------------------------------------------------------------------------------------------------------------
Power to DUT                                                As Required                              As Required


4.5.3 Test Procedure

                            Fig. 4-5 ── Two-Tone Transmit IMD Test Hook-up


4.5.3.1 Turn on the DUT, RF wattmeter and spectrum analyzer and set the following controls:

Instrument                                                Control                                     Position
DUT                                                          Mode                                          LSB
                                                               Band Selector                            80 Meters
                                                               Frequency                                  3.900 00 MHz

                        
                                                                     XMIT/RCV                                RECEIVE
                                                             DRIVE or RF LEVEL                        Minimum
                                                                Microphone                                    Minimum

Two-Tone Generator                                     TONE A (700 Hz)                               OFF
                                                                   TONE B (1900 Hz)                             OFF
                                                                   HI-Z/LO-Z                                      As Required
                                                                   BALANCE                                          Center
                                                                       LEVEL                                           Full CCW
                                                                   Attenuator                                         –30 dB

RF Wattmeter                                               Mode Select                                           “T”

Step Attn                                                      Attenuator                                           –40 dB


Spectrum Analyzer                           CENTER FREQ (FREQUENCY)        03.89870 MHz
(Menu in Parentheses)                                     SPAN (SPAN)                          20 kHz
                                                                REF LEV (AMPLITUDE)                 –40 dBm
                                                                   ATTEN (AMPLITUDE)                    20 dB

                                                                   RES BW (BW)                                 100 Hz
                                                                   VIDEO BW (BW)                              10 kHz
                                                                  THRESHOLD (DISPLAY)               –110 dBm
                                                                  SWP TIME (SWEEP)                          AUTO


4.5.3.2   NOTE: If proceeding from the previous tests, this paragraph may be skipped.

Receiver hiss should be heard; adjust the volume to the desired level. Allow all equipment at least 10 minutes warm-up time before proceeding to step 4.5.3.3.


4.5.3.3  Tune the DUT per the operator's manual for the test frequency of 3.900 MHz. Turn on the two-tone generator and set both tone switches to ON. With the DUT in the LSB mode, set the generator LEVEL and ATTENUATOR controls for the maximum audio input as specified by the manufacturer. If the manufacturer does not list a specification for this figure, adjust the 2-tone generator’s amplitude for maximum rated RF output of the transmitter with the transmitter’s microphone gain near maximum. Observe the transmitter power as shown by the wattmeter. Ensure that the output power of the DUT is not greater than the manufacture's maximum power output rating. Unkey the transmitter and set the step attenuators for approximately -46 dBm input to the spectrum analyzer.

              CAUTION: The input to the spectrum analyzer at no time should exceed 0 dBm.


4.5.3.4   Place the DUT in the VOX mode and verify operation with the signal generator. Note on data sheet if VOX does not function correctly. Return the DUT to the PTT mode and key the transmitter. Set the BALANCE control on the generator for equal tone amplitude as shown on the display. Adjust the CENTER FREQ, if necessary, so that the display center is half-way between the two pips. The IMD-distortion products should now be visible.


4.5.3.5   Adjust the REF LEVEL control (and step attenuators, if necessary) for the peak of the two pips to be at –6 dB. The spectrum analyzer is now calibrated. The amplitude of each IMD distortion product may now be read in dB PEP (dB below the peak envelope power) directly from the display.


4.5.3.6   Manipulate, if necessary, the two-tone generator audio LEVEL and the transmitter audio gain and drive control to obtain the lowest possible IMD products. If this is done, the spectrum analyzer REF LEVEL control (and possibly the step attenuators) may need to be reset for tone pips of –6 dB.


4.5.3.7  Set the SWP TIME (in the SWEEP menu) for 6 seconds. Take a single sweep by depressing the SGL SWEEP button. Record all info on data sheet. Print and save to an appropriate file name.


4.5.3.8  Set and tune the transmitter for USB at a frequency of 14.250 MHz. Set the CENTER FREQ for 14.25130 MHz. and return the SWP TIME back to AUTO. Repeat paragraphs 4.5.3.3 to 4.5.3.7 for this frequency.


4.5.3.9  Repeat step 4.5.3.8 for the following frequencies (if applicable to the DUT): 1.850 MHz, 7.250 MHz, 10.120 MHz, 18.120 MHz, 21.250 MHz, 24.950 MHz, 28.350 MHz, 50.200 MHz, 144.200 MHz and 432.200 MHz.  

These are not "cherry-picked" watts (or tones), as the tone levels are adjusted until the rig is outputting its rated max PEP output, and then the step attenuators are adjusted so the signal peaks are 6 dB below the reference level on the spectrum analyzer. as we all know that the analyzer IS showing the combined tones at PEP....I explained this in some detail a few years ago, but don't have the time tonight, so I'll just quote an article. :)
From Keith Barkley in June 2001 RF Design Magazine:
Quote
[Remember that] PEP is the maximum instantaneous power of the combination of the two signals. A two-tone signal looks  similar to an AM modulated tone. The envelope of the RF signal varies as a sinusoidal with a frequency of Δf. When the voltages of f1 and f2 are out of phase, they cancel and the envelope is at a null.  When the two voltages are in-phase, they  add, and the voltage at the instantaneous peak is twice that of either tone. Because power is equal to the square of the voltage divided by the resistance, when the voltage increases by a factor of two, the power increases by a factor of 2 squared, or four.

Therefore, the PEP is four times the per-tone power and twice the average.

....If a peak reading power meter is used [as in the ARRL testing] to measure the PEP directly, that fact should be noted with the results...

Whether someone wishes to report the results directly off the analyzer screen referenced from one-tone (and list them as "dbc") or report the results directly off the analyzer screen, referenced from the "reference level"/PEP level (and list them as "db PEP"), the difference is 6db...
Anyone can add or subtract 6db as needed to allow you to have the numbers you like to see, but the IMD level is exactly the same!  It's just written differently, and there is no "cherry picking" here.  :)


As for the "tones"....use of non-harmonically-related audio tones (between 300hz and 3000hz), spaced at least 1000hz apart, for IMD testing of communications equipment was established by Bell Labs many years before I was born...(and I think even decades before Carl was born..:)
I don't think the ARRL is doing anything other than what has been accepted engineering practice for many years (decades!!)


FYI, mini-circuits, HP, Motorola, Tek, Agilent, etc. all have similar tech notes and will provide detailed test procedures for anyone interested in their equipment...I just happen to have RF Design article handy to quote from...



3)  As for "compression", "limiting", etc..
In my opinion, this is kind of a red herring in this post, since we're talking about test procedures where no compression/processing/limiting is engaged.......hence I won't dwell on it...
But, assuming you're talking about operating and not "testing", who is gonna write these rules?? :)
Not to mention that properly done, speech processing/compression can actually improve things...and nowadays it's done in DSP and (as long as the level isn't too high) does NOT adversely effect transmit IMD, so I agree with you here...but, again, who's gonna write those rules?  :)
1. Limit ALL ham rigs to no more than 5-6dB of compression/limiting, no more than rated output (which includes internal power controls), and restrict the maximum amount of the audio gain by software sampling the RF output level.
Minimal added engineering required and even opened up still acceptable specs/performance on marine and other commercial channels.

2. White noise IMD testing goes back over 50 years from my own personal experience with military products and their acceptance testing including HF amps in the 1-10KW range....using tetrodes.

Carl
 Yeah, white noise has been used for a long time....but two-tone testing has as well!!



Hope this clarifies things for all of you. :)
Gotta go!

 73,
John,  KA4WJA


Title: RE: Ham Xcvrs' and Amps', Transmit Spectral Purity, IMD Products, vs. comm/maritime
Post by: KA4WJA on February 11, 2018, 08:28:51 PM
Brian,
We did cover that in that other thread you linked to.
And, I don't feel like rehashing it here. :)

In a nutshell, I cannot fathom a company like Icom (or the lab they hired) forging FCC application docs....and I have friends that work in EMC compliance labs, let me assure you the FCC is there all the frigging time!  (our tax dollars at work)

So, while others might not have found the results that were submitted to the FCC, I don't doubt that it did meet those numbers....
(parts changes, minor circuit changes, etc. can all be a cause of these disparate results)

But, whatever the case, fact is most of our modern ham rigs are significantly worse in regards to transmit IMD than they need to be, and it will not cost a lot to do it!  :)
(heck, just look at the TS-590SG...it's not perfect, but a fair sight better than many of the others these days, and it's not a wicked expensive rig...)


Not sure this clarifies things, but have a look at that thread...
 


73,
John,  KA4WJA


Title: RE: Ham Xcvrs' and Amps', Transmit Spectral Purity, IMD Products, vs. comm/maritime
Post by: ZL4IV on February 12, 2018, 02:57:56 AM
So all you guy's are telling me that decades ago when I sat my license is no longer valid. I now have to conform to spectrum purity because the test gear has been now affordable to to armchair critics makes my license useless ? Can't you guy's get the true nature of HAM radio? If the guy's wide tell him, if he is splattering everywhere tell him. Oh that's right, some of us have just become users and cant fix problems. So we all have to be dumb down and everything produced just perfect.

In my shack I have so much test gear I could find fault with just about anything. If somebody makes a crap AMP then the market will judge and not buy. If a Ham makes a crap Amp then the few of us left will help get it right for them. This goes for all radio equipment, we are here to help not condemn. Oh bring back the days of knowing the nets started 10KHz up, spill over to other bands, looking for the fundamental signal, don't you guy's miss that? AM (DSB) were the days, agree? Relax, in the real world of HAM most the criticism come from bored tech's. BTW where are you? the HF bands are open, I have 10m contacts every other day and all the bands below are open every day sometime. Give me a call. analyze me, like to check you also.

Relax, it's not a knowledge contest, it just fun, cul.

ZL4IV




Title: RE: Ham Xcvrs' and Amps', Transmit Spectral Purity, IMD Products, vs. comm/maritime
Post by: VK6HP on February 12, 2018, 05:23:48 AM
Why would anyone expect standards or knowledge to remain static in the face of technology changes and more widely accessible data?  To do so would reduce support for ham radio's continued existence - and that reduced support would be justified. Ignorance is not bliss, and life in a comfortable fog is no way to live.

I don't agree that the market alone will sort things out.  A "watt is not a watt" (to paraphrase) and, indeed, some people do buy rubbish radios that an operator with standards would be ashamed to put on the air. It's all about taking personal responsibility and using the available data, gleaned either from tests we do ourselves using increasingly accessible RF test equipment, or from the work of others.

I commend John (KA4WJA) for posting the data.  They'll always be recalcitrants for whom no amount of engineering science is convincing but let's not be disheartened by that: if it makes thoughtful, objective operators think twice at the time of their next purchase, that's progress. It's perfectly reasonable to insist that your next transmitter be cleaner than your last.  In my case I'll have no hesitation in declaring a new SDR/LMOS amp combination a failure if it can't outdo my TS-590 or TS-830 or, more interestingly, my 50 year old Collins S-line/30L-1.

73, Peter.


Title: RE: Ham Xcvrs' and Amps', Transmit Spectral Purity, IMD Products, vs. comm/maritime
Post by: KM1H on February 12, 2018, 05:13:54 PM
Quote
Hope this clarifies things for all of you. Smiley
Gotta go!

 73,
John,  KA4WJA

About 2-3 sentences were all that was needed to determine the method you used which is the ARRL's version which results in a 6dB improvement versus the long established professional way of measuring which is against a single tone.

It has also been known for decades that the ARRL cherry picks the two tones for the best results.The ARRL caters to their advertisers who use the same fraudulent method and does not want uneducated hams to see how bad some of the crap on the market really is. I believe we have been thru this before.

Here is a quick paper on what you and everyone else should be measuring, the rest is pure garbage IMO.

Carl


Title: RE: Ham Xcvrs' and Amps', Transmit Spectral Purity, IMD Products, vs. comm/maritime
Post by: KA4WJA on February 15, 2018, 11:03:14 AM
Hello again,

I got a couple e-mails asking some things that I've been hesitant to add here, as I don't wish to turn anyone off by "info overload" :)

Then thought, more knowledge is a good thing, so maybe I should try again to lay out some facts that many hams will find helpful??  Please remember that I'm not some random yahoo ranting on the internet (such as "Zenki"), I've been a ham 75% of my life, and there is some helpful info here, that I hope will not get lost in an argument.  :)

But, what to actually do??  How to get the facts out there, without the controversy?? Hmmm??

How about expressing some (common?) opinions first, and then hopefully we can get to the facts?  So here goes.


1)  I've been a member of the ARRL since 1974 (except for a one-year lapse), and while I do NOT agree with a good deal of their political (FCC) posture, nor do I appreciate their "editorializing" facts, or "factualizing" editorial comment (means they portray their opinions as facts), I'm still a member....mostly for the resources and to show the gov't that there are quite a few hams that are active (so we don't lose more of our spectrum!)

In my opinion ARRL HQ staff are just people who want to keep their job, and nobody wants to rock the boat...I suspect few have any real "love" for radio...(you know "amateur" comes from the "ama" / "amo", the latin root-word for love)

The factualizing of opinion is disturbingly insulting to me, and the lack of attention to real-world use of the airwaves is very disillusioning!  

I find their minimal attention to transmit IMD to be frustrating, but their two-faced attitude where they pay lip-service to the desire for good transmit IMD in a sentence or two of text, and then show fancy color graphics with 3rd order IMD ranges from -20db(PEP) to -35db(PEP), with -30db(PEP) showing "good", and rigs that test out with just a -23db(PEP)  to - 25db(PEP), with only a casual 3 word comment, while raving about the visual appearance / ease of use...Well this is truly sad!!!  :( :(

Further, we all know that static two-tone (or static white noise) transmit IMD testing, shows the best performance the transmitter or amplifier will generally have...but they never mention that!  
{Dynamic testing, where two-tones are dithered by a third tone, can show power supply deficiencies and circuit anomalies, that result in worse IMD....these tests are highly recommended today for external amps, to show their design and power supply issues, but the ARRL never talks about this!}

I'm also frustrated by ARRL HQ's lack of concern with real every-day hams, but somehow if you're a big contester or dx'er, you and your agenda gets instant and lengthy attention??

Oh, and don't get me started regarding their support of the no-code HF license!  I mean really??  Even I learned CW well enough to pass the test....but, truth-be-told, I couldn't copy 20wpm now to save my life!

I suppose the list of gripes about the ARRL could go on and on, but I think you see the point! :)  
Just, because the ARRL isn't perfect (what is?) and just because they frustrate me, etc., in MY OPINION, these are not reasons to discount all of their efforts....so let's look at what they do that is good, in regards to this discussion here.  :)

They use professionally accepted test methods (EIA/ECIA, Bell Labs, Motorola, etc.), many of which were designed and perfected over many decades...

No, even these are not perfect, I mean yeah a static two-tone isn't the best test, but it IS the data that we have for dozens of amps, and dozens & dozens of rigs, over the last 50 years, with transmit IMD all tested using the same method...so why not simply use this data to compare various radios and amps, compare and contrast various designs, etc., and learn what some rigs and amps are doing to pollute our airwaves, and to make purchase decisions??

Any ham that can't subtract 6db (or add 6db) to a spec if trying to compare to a result from a different test method, probably will not have sufficient knowledge of Inter-Modulation Distortion and Occupied Bandwidth, that would allow them to understand the importance of what we're discussing here.....so, I don't think this should be an issue.  :)

So, why not just use the info??

We can still gripe about some other issues with the ARRL, but why not use the data and resources they provide to improve ham radio??  

After all, from Part 97, the 5 basic reasons / purposes of the Amateur Radio Service are:

The rules and regulations in this part are designed to provide an amateur radio service having a fundamental purpose as expressed in the following principles:

(a) Recognition and enhancement of the value of the amateur service to the public as a voluntary noncommercial communication service, particularly with respect to providing emergency communications.

(b) Continuation and extension of the amateur's proven ability to contribute to the advancement of the radio art.

(c) Encouragement and improvement of the amateur service through rules which provide for advancing skills in both the communication and technical phases of the art.

(d) Expansion of the existing reservoir within the amateur radio service of trained operators, technicians, and electronics experts.

(e) Continuation and extension of the amateur's unique ability to enhance international goodwill.


So, to advance the radio art, advance the skills in both the communications and technical phases of the art, expand the reservoir of technicians and electronic experts, and enhance international goodwill....4 of the 5 purposes above...having a clean transmitter and allowing others to use the airwaves without adverse interference, and learning about how this is done, etc., actually does accomplish 4 of the 5 of these....so...

How about we look at what we are trying to accomplish here...inform and educate our fellow hams, regarding reduction of on-air transmit interference (and hence allow those of you who bought 90db to 100db dynamic range radios, to actually get close to being able to use much of that potential).

So again, I ask...why not use the test data we have (from ARRL) and expertise of many experienced engineers (from Bell Labs, Motorola, HP, R&S, etc. etc.), to both learn about these topics and improve our on-air signals??


2)  Yep, static two-tone testing isn't the best.....But, the ARRL does use the standard, professionally accepted tones in transmit IMD testing....these are not "cherry picked" tones...

The use of two non-harmonically-related audio tones, between 300hz and 3400hz (spaced 1000hz apart), for SSB IMD testing, was established by "the phone company" (Bell Labs) in the 1930's (no, that's not a typo, the 1930's) for use in their multiplexed telephone network (in the late 1940's thru the late 80's this expanded to multiplexed radio / microwave telephone transmissions...and multiplexed baseband FDM Satcom telephony)  Their original tones were 800hz and 1800hz, I believe.

Parallel to this (from the 30's thru the 80's) were RCA, Westinghouse, GE, Motorola, etc....and harris, rockwell, etc. etc., all experimenting with radio comms and incorporating SSB experimentation, etc.

At some point (1950's I think) as more capacity was needed and technology improved, and as radio comms was coming into the forefront, most SSB baseband was reduced to 300hz to 3000hz...(it wasn't until the early 80's that this change was officially made in the world of HF maritime comms, when the int'l freq assignments were changed)

With wider spacing of the tones, the wider the occupied bandwidth is, the choice of increasing spacing of IMD test tones, for communications equipment, to 1200hz was made, with tones of 700hz and 1900hz, to better replicate the IMD results of the average male voice...and these 700hz and 1900hz tones were chosen by most RF engineering departments involved in radio comms...(there are some testers that use 400hz and 1800hz, and yes these show somewhat wider occupied bandwidth, as the wider spacing of the tones does widen-out the transmitter bandwidth)

The earliest use I had of these was in High School in the 1970's....and while I assume the ARRL was also using these tones as early as SSB was in in its infancy on the ham bands / the 1950's, (before I was born).....the earliest I have actual ARRL transmit IMD specs from is the 1970's.  :)

So, there is no tone cherry-picking going on here by the ARRL.  :)


3)  So what about this mumbo-jumbo about ARRL numbers being 6db better??

Well, the numbers are 6db better, but the actual figures are the same!!

How can that be, you ask??

Well, for SSB transmitters a 3rd order IMD spec of -30dbc IS the same as -36db(PEP)....so the ARRL reported IMD (referenced to PEP) is -36db, does "look" like 6db better than -30dbc....but one is -36db(PEP) and the other is -30dbc...and in actual fact they are the same!!!

Earlier / above, I detailed the reasons why the analyzer display shows what it does, with the 2 -tones representing the radio operating at its rated max PEP output (typically 100watts)...

(http://i67.tinypic.com/2hdsnde.jpg)

(this example image is an IC-781 at 150 watts PEP)

Quote
[Remember that] PEP is the maximum instantaneous power of the combination of the two signals. A two-tone signal looks  similar to an AM modulated tone. The envelope of the RF signal varies as a sinusoidal with a frequency of Δf. When the voltages of f1 and f2 are out of phase, they cancel and the envelope is at a null.  When the two voltages are in-phase, they  add, and the voltage at the instantaneous peak is twice that of either tone. Because power is equal to the square of the voltage divided by the resistance, when the voltage increases by a factor of two, the power increases by a factor of 2 squared, or four.

Therefore, the PEP is four times the per-tone power and twice the average.

....If a peak reading power meter is used [as in the ARRL testing] to measure the PEP directly, that fact should be noted with the results...


But, it seems more / different writings on this are needed here??

So, from the 1980's, from the late Helge Granberg, Motorola RF engineer:


Quote
Figure 1
(http://i65.tinypic.com/2gy7z9y.png)
Figure1 shows a low distortion, two-tone envelope displayed on
an Oscilloscope screen.


Figure 2
(http://i65.tinypic.com/1566788.png)
Figure 2 shows on a spectrum analyzer screen the same
signal displays as two discrete frequencies separated by the
difference of the audio frequency or frequencies.

The display represents the rate at which peak power
occurs when the two frequencies are in phase and the
voltages add. Thus, one peak contains one-fourth (-- 6 dB)
of the peak envelope power (PEP). An average reading
power meter would read the combined power of the tones,
or half the PEP, assuming the envelope distortion is
negligible. The third order distortion products (d3), fifth order
(d5), etc., can be seen on each side of the tones. The actual
power (PEP) of each distortion product can be obtained by
deducting the number of decibels indicated by the analyzer.


Now that the actual display is understood, let's get back to this myth that the ARRL numbers are fudged?? Or overly generous??  Of course they are not fudged!  And, they are not generous....you just need to look at the qualifier "(PEP)"  vs.  "c".

As I wrote above -30dbc is the same as -36db(PEP)...

The "dbc" figure is the older, so-called "mil-standard" and the "db(PEP)" is the newer, EIA/ECIA standard (from the 1970's/80's), and this EIA standard was also used by the FCC (and ITU) for many communications specs...the "dbc" figure is the IMD referenced to the the level of the tones on the analyzer (and the tones display at 6db below PEP)...the "db(PEP)" figure is the IMD referenced to PEP...


Now, if you want a more official statement on this....here 'ya go:
Again, quoted from the late Helge Granberg:
Quote
"In one method, the military standard (1131 A-2204B), the distortion products are referenced to one of the two tones of the test signal.....in the second method, (the EIA/ECIA standard), the amplitude of the distortion products is referenced to the peak envelope power, which is 6 dB higher in power than that represented by one of the two tones.

An amplifier or device indicating a maximum distortion level of -30 dB in first method (Mil Standard) represents -36 dB with the second method (EIA/ECIA standard). Conversely, a -30 dB reading with ElA’/ECIA's PEP reference would be -24 dB when measured with the more conservative military method.

In practical measurements, the two tones can be adjusted [by the analyzer's internal, or an external, input attenuator or reference level adjustment] 6 dB down from the zero dB line, and direct IMD readings can be obtained on the calibrated scale of the analyzer.
Alternatively, the tone peaks can be set to the zero dB level and 6 dB deducted from the actual reading."

So, the "db(PEP)" numbers are not inflated, they are just 6db higher than the "dbc" numbers, but they represent the exact same level....

If a 100-watt (+50dbm) PEP radio's 3rd order IMD product is say -30db(PEP), that means that specific product is 1/10 of a watt (+20dbm), which is the same as -24dbc, as the "c" is already displayed 6db below PEP...


4)   Finally, some may wish to argue about solid-state vs. vacuum tube, or 50vdc vs. 13.8vdc solid-state PA's...but don't get too wrapped up in that, as there is even more to this...some have e-mailed and asked about the variations in transmit IMD, from similar / same transistors or tubes???

PA circuit design and construction plays a role here, but also so does the exact biasing and tuning of that particular PA.....usually, biasing an amplifier more toward class B will cause the lower order distortion products to go down, and the amplitudes of the higher order products to increase, and this is one way some manufacturers claim (and actually attain) a somewhat acceptable 3rd order spec, that they can advertise, but this is at the expense of increased higher order IMD...heavier biasing in AB (closer to A), can usually reduce the higher order products, but of course at the expense of efficiency, etc. (and sometimes an increase in lower order products).
In some designs, there is also a bias point where the 3rd order and 5th order products can be equal...

You may find it interesting to learn how can one 100-watt radio can have such different IMD specs from another (or how can one HF amp have varying IMD specs than another amp), when many of them use the same or similar devices (transistors, tubes, etc.)...have a look at the different results of lower-order and higher-order IMD products of the Elecraft K3s, depending on the PA circuit tuning and biasing...(please know I'm not picking on Elecraft, they're a great bunch of guys! It's just that the K3s is only rig that I have ARRL test results for, for different PA tuning/adjustments...so that's the example above I'm referring you to :) )


I know there is a lot here, and as I wrote up front I don't wish to overwhelm anyone, but do wish to better inform.  Hope I've done that??  :)


73,

John,  KA4WJA




Title: RE: Ham Xcvrs' and Amps', Transmit Spectral Purity, IMD Products, vs. comm/maritime
Post by: W1VT on February 15, 2018, 11:31:35 AM
In May 1992 I published a 5 watt class A amp using the MRF 137.  The 3rd order products were -32 dB relative to each tone and the 5ths were -55 dB relative to each tone.  A couple of amps were built for lab use.  I also built a version using the MRF 138, which I used to replace the final in a Drake TR-7 to get a rave review from an audiophile that worked at ARRL HQ at the time--my audio sounded exactly like me while I was running a pileup on 75M in the Phone Sweepstakes.  With just 4 watts to a full wave loop.  ;D

It generated a letter to the editor how they shouldn't publish stuff that needed a 28 volt power supply.  He was only interested in designs that ran off of 12 volts.

I never did much more than that concerning the issue of transmit IMD--I was living it what may have been the cheapest single bedroom apartment in Newington at $220 a month. It didn't have enough AC to run a 100 watt rig without lights blinking, much less run high power.  Instead, I figured out how to get to the best VHF+ contest location within 4 hours of Newington and proceeded to amass a collection of grid and contest awards over the next six years.  I built a 50MHz to 10 GHz portable station--good enough to get grid awards on six microwave bands.  I have 902MHz quarter century grid award #25.  In 1995 I was awarded the John T. Chambers award for my outstanding contributions to VHF and UHF amateur radio by the Central States VHF Society.

Zak W1VT


Title: RE: Ham Xcvrs' and Amps', Transmit Spectral Purity, IMD Products, vs. comm/maritime
Post by: KA4WJA on February 15, 2018, 12:18:57 PM
Zack,
Awesome!

Many years ago, I built a 28-vdc PA for my 2m tranvtr.
I used a VMP-4..
It had decent IMD (3rd => -40 /  5th=> -50db) at 7 to 10 watts out (more than I needed, and all my 28-volt supply would allow for 100% duty-cycle), but I found an out-of-band spur (down about 40db, but still...)
Frustrated, but found no spur at 4 watts out, or below...
(ended up only needing 2 to 3 watts out, to drive a SS IPA and then to pair of 8874's, so it worked great for EME....no spurs and no IMD issues)


BTW, I went to school up your way...Worcester Poly Tech...although that was quite a while ago.
Still remember our station, W1YK, nice towers on top of a big 5/6-story building, on top of a big hill!


73,
John,  KA4WJA


Title: RE: Ham Xcvrs' and Amps', Transmit Spectral Purity, IMD Products, vs. comm/maritime
Post by: AA2UK on February 15, 2018, 03:19:16 PM
Zak, I was looking at some of your QSL's for working you on the Microwave bands in the mid to late 1990's. I just pulled out one from 1997 where we worked on 10gHz you were potable in FN42bl Mt. Wachusett and when you were in FN33kd on Mt Equinox. I also worked you when you were KH6CP/1 also on Equinox on 2304. I was at my home station for all these Q's from Sweetwater, NJ FM29qo.
Boy do I miss that location.
73, Bill AA2UK


Title: RE: Ham Xcvrs' and Amps', Transmit Spectral Purity, IMD Products, vs. comm/maritime
Post by: K6AER on February 15, 2018, 07:41:51 PM
As long as mic. compression and mic, gain are adjustable on the radios the whole IMD discussion is a mote point. Every day I see terrible signals on the band. Worrying about IMD that is -30  or -40 dB on the third and fifth is a waist of time with the all knobs-to-the-right crowd.


Title: RE: Ham Xcvrs' and Amps', Transmit Spectral Purity, IMD Products, vs. comm/maritime
Post by: AC2RY on February 15, 2018, 08:09:53 PM
As long as mic. compression and mic, gain are adjustable on the radios the whole IMD discussion is a mote point. Every day I see terrible signals on the band. Worrying about IMD that is -30  or -40 dB on the third and fifth is a waist of time with the all knobs-to-the-right crowd.

Audio signal compression should not be a problem in radio where SSB signal is synthesized digitally. Resulting signal can be digitally filtered to eliminate anything beyond passband before upconverting to carrier frequency. Even better can be done in direct sampling radios - where you can implement brickwall filtering directly at carrier frequency right before DAC. And there is usually no significant IMD caused by low power analog circuits.


Title: RE: Ham Xcvrs' and Amps', Transmit Spectral Purity, IMD Products, vs. comm/maritime
Post by: KA4WJA on February 15, 2018, 08:23:40 PM
Mike,
Thank you for contributing here.
And yes, as we have both agreed here before, the "all knobs to the right crowd" are the worst offenders...
But, forgive me for disagreeing with your other opinion here....because in my opinion understanding transmit IMD and using transmit IMD and spectral purity as criteria in making purchase decisions, is a good thing!!

Yes, a -30db or -40db 3rd and 5th is probably meaningless with those who have cranked everything to the right....but, what about the remaining 95% of hams??
Are we to simply say, "hey, don't worry about IMD...you're not splattering as bad as another guy." 
Or, do we just give up and say, "you don't need to know anything about this...the manufacturers wouldn't sell a rig that wasn't 'good enough' "??
Really??  How is either of those promoting good engineering and good amateur practice??
 
As long as mic. compression and mic, gain are adjustable on the radios the whole IMD discussion is a mote point. Every day I see terrible signals on the band. Worrying about IMD that is -30  or -40 dB on the third and fifth is a waist of time with the all knobs-to-the-right crowd.

As I wrote right up front that one of the 3 reasons I posted all the above info was that I'm considering a new rig...and if I didn't want a rig with knobs (I do), I'd order an ANAN-8000D tomorrow!

And, if you read what I wrote a couple days ago: 
I hope this helps some understand what our modern HF rigs are doing to pollute the airwaves, even if they're operated with "good amateur practice", in accordance with the factory operations manual, etc...(now, if you crank-up the mic gain on most rigs, things will get worse....and many times, they'll get really bad....but, if you start with a bad rig, it's bad no matter what and things get really bad very quickly...and if you start with a good rig, things are better from the start and might be "okay")


The 40-odd radios above represent most of the popular HF rigs on the ham bands today and sold in the past 30 - 40 years, as well as a few that are very new (and some so obscenely expensive that few hams will ever operate one)....oh, and 25 of the above 40 rigs, also find themselves in the top 30 of the rigs listed by "narrow-spaced (2khz) 3rd-order rec IMD" on Rob Sherwood's list, maybe now some will see the red herring that buying a rig from a "list" can be? :) 
 
I think you'll see that while I also mentioned mic gain, the fact is that some rigs are better than others, even when operated "perfectly" / as prescribed...
(btw, well designed speech compression, or even RF clipping/processors if not done too heavily, have no measurable detriment to transmit IMD....and in actual practice, they can improve things some, as reducing the peak-to-average ratio, reduces stress power supplies / allows better power supply caused IMD..)

How may hams have publically said to Rob that there's no need to worry about radios with excellent receivers, 'cuz there are so many guys turning their mic gain up and splattering, the receiver specs are meaningless??
{now in reality, this position is not that far off-the-mark...cuz the limiting factor of most HF ham rigs' receivers these days are the transmitters of the other stations on-the-air...and I've seen Rob say/write this himself...but, everyone is still looking at his list and discussing which rig to buy, based on that list.. :) }



Mike, as in the past, I do respect your expertise and do not wish to argue the point above...
We just have a difference of opinion, regarding whether transmit IMD figures should be used in purchasing decisions...


73,
John,  KA4WJA 



Title: RE: Ham Xcvrs' and Amps', Transmit Spectral Purity, IMD Products, vs. comm/maritime
Post by: K6AER on February 17, 2018, 03:15:04 PM
John,

This dilemma comes down to marketing. Ninety percent of the signals on the ham bands are less than 20 dB above the noise floor. Having an IMD better than 30/40 dB (third/fifth),in my opinion, will never sell for the 100 watt, G5RV entry level crowd. They don’t care or don’t feel this is a necessary goal to pay for.

Now for those who have been the hobby for a while, running 1500 watts to a large Yagi array, 30/40 dB IMD is not enough. I put up a 4 element SteppIR at 105 feet and had to I sell a very nice TS-570SG for the radio had acceptable IMD performance but was not good enough. I bought a IC-7600 just so my signal would be spectrally cleaner. Still, having a S9+30 dB signal radio performance will show where the IMD limits are no matter who makes the exciter.  

The radios you mention are indeed vary good but entry level hams will not spend $2000 or more just to work HF. Remember this is not a problem with commercial radios for they have minimum channel spacing. Only hams butt up to another QSO, 3 kHz away.

Another point is the HiFi ESSB crowd that want bass response going down to 30 Hz. These settings just make the radio into an overpriced, high power, marker generator. You see these signals all the time with markers sprouting all through the spectrum of their signal.

Bottom line is I do not believe the great majority of HF hams will spend 60% more on a radio for 10 dB of better IMD performance.


Title: RE: Ham Xcvrs' and Amps', Transmit Spectral Purity, IMD Products, vs. comm/maritime
Post by: K6BRN on February 17, 2018, 05:55:19 PM
Transmit IMD.  Such a critical and hot topic to the ham radio community.  On this forum, anyway. 

Oddly enough, in over three decades of QSOs, its never come up during a QSO.  Never had a contact say "Wow!  Great IMD performance!  And just LOVE that low end (Hi=Fi ESSB)!"  Or conversely....  "Ugh!  You REEK of IMD!  How gauche!"  No DXpedition has ever refused my call:  "Ack!  Fix your IMD!  You're blotting out Monrovia entirely! (Monrovia, CA of course... always at the top of everyone's most wanted call list)"  On SSB, RTTY or CW.

Yes, some have linked IMD to global warming.  And recycled SB-200 amplifiers.  But not so much to real, actual, verified, widespread and tragic problems on the air waves.  Though there are those who would claim otherwise.  Like the ever anonymous "Z".  (enki).

So, in conclusion, there are probably better topics to obsess over.  Air pollution.  UFOs.  Secret recipes for cookies. You know.  The usual suspects.  However, I do recognize that this topic seems to be the favorite subject of the OCD club.  So, in the spirit of medicinal obsessions... carry on!



Title: RE: Ham Xcvrs' and Amps', Transmit Spectral Purity, IMD Products, vs. comm/maritime
Post by: AC2RY on February 18, 2018, 09:30:16 PM
Transmit IMD.  Such a critical and hot topic to the ham radio community.  On this forum, anyway. 

Oddly enough, in over three decades of QSOs, its never come up during a QSO.  Never had a contact say "Wow!  Great IMD performance!  And just LOVE that low end (Hi=Fi ESSB)!"  Or conversely....  "Ugh!  You REEK of IMD!  How gauche!"  No DXpedition has ever refused my call:  "Ack!  Fix your IMD!  You're blotting out Monrovia entirely! (Monrovia, CA of course... always at the top of everyone's most wanted call list)"  On SSB, RTTY or CW.

Yes, some have linked IMD to global warming.  And recycled SB-200 amplifiers.  But not so much to real, actual, verified, widespread and tragic problems on the air waves.  Though there are those who would claim otherwise.  Like the ever anonymous "Z".  (enki).

So, in conclusion, there are probably better topics to obsess over.  Air pollution.  UFOs.  Secret recipes for cookies. You know.  The usual suspects.  However, I do recognize that this topic seems to be the favorite subject of the OCD club.  So, in the spirit of medicinal obsessions... carry on!



Transmit IMD becomes hot topic for me each time when I hear splatter from SSB station more than 3 kHz away.


Title: RE: Ham Xcvrs' and Amps', Transmit Spectral Purity, IMD Products, vs. comm/maritime
Post by: K6BRN on February 19, 2018, 01:22:41 PM
Hi Tom:

So you see a lot splatter and its all due to IMD because of poorly designed and built radios and amps?  Are you sure it's not front end overload?  Or a mistuned tube amp?  Or our ESSB friends who love to spread out over many KHz (same for AM, BTW).  Or the novice FT/JT operators who crank up their soundcard TX levels too high and whose radios faithfully transmit baseband audio distortion across a number of KHz.

Because that's all just operator error, not bad radios or amps.  And all those operators are ... well ... amateurs.  So they make mistakes.  And (usually) correct them after a time.  Its a hobby, after all.  The fate of the world does not wait on amateur radio.

And you think 3 KHz spacing is more than adequate for SSB? Interesting.  Because it's really not.  There has to be reasonable standoff spacing to allow ever-imperfect filters to do their jobs.  Bandwidth is often specified as the 3db or 6 db down point.  But filter rolloff continues for quie some time after that.  The further away from the signal you are the better.  For SSB, 3 KHz is pretty bad spacing. 

Then there are the simply large signals...  Sideband suppression and other products may be attenuated by 30 or even 40 db (1,000x to 10,000x).  But when you are sitting right next to a neighbor running full legal limit (it IS a down solar cycle, after all) whose antenna is within 50-300 feet of yours, those products will be very significant, and so will the receiver desense on the same band.  Even if he or she is a really nice person.  I have exactly that situation in the dense urban neighborhood I'm in.  Much of Long Island is similar.

Blame it on the equipment?  Not really a good idea.  The hame radio market is small, almost universally cheap (that is, hams with thick wallets are a small percentage of a small percentage) and premium performance commands a premium price.  Not that current equipment does not do quite well within its price/performance constraints.  Could we do better?  Probably.  What are you going to give up?  Price?  TX efficiency?  Power? Size?  Weight?

The market has decided what amateurs will bear in all of these categories.  And the FCC guidelines pretty much make sure that some reasonable limits exist within which we can all operate.  Expecting perfection?  That's in the next life.


Title: RE: Ham Xcvrs' and Amps', Transmit Spectral Purity, IMD Products, vs. comm/maritime
Post by: AC2RY on February 19, 2018, 07:41:51 PM

And you think 3 KHz spacing is more than adequate for SSB? Interesting.  Because it's really not.  There has to be reasonable standoff spacing to allow ever-imperfect filters to do their jobs.  Bandwidth is often specified as the 3db or 6 db down point.  But filter rolloff continues for quie some time after that.  The further away from the signal you are the better.  For SSB, 3 KHz is pretty bad spacing. 

Then there are the simply large signals...  Sideband suppression and other products may be attenuated by 30 or even 40 db (1,000x to 10,000x).  But when you are sitting right next to a neighbor running full legal limit (it IS a down solar cycle, after all) whose antenna is within 50-300 feet of yours, those products will be very significant, and so will the receiver desense on the same band.  Even if he or she is a really nice person.  I have exactly that situation in the dense urban neighborhood I'm in.  Much of Long Island is similar.


Gone are the days when SSB filtering was done by analog circuits. Today it is almost universally processed by DSP with digital filters with brickwall (-60 dB or better) properties either at IF (most radios) or right at carrier frequency (in direct sampling radios). It does not mater how much microphone is overdriven - input could be a white noise for that matter. Low signal analog circuits do not produce much of IMD to speak about. Thus the only source of IMD TODAY is power amplifier, either one in radio itself, or external linear.

Regarding the location  - those with splatter are rarely local. And I can find a lot of loud (S9+10) signals on the band that do not spill over 3 kHz away.




Title: RE: Ham Xcvrs' and Amps', Transmit Spectral Purity, IMD Products, vs. comm/maritime
Post by: K6AER on February 19, 2018, 08:14:52 PM

And you think 3 KHz spacing is more than adequate for SSB? Interesting.  Because it's really not.  There has to be reasonable standoff spacing to allow ever-imperfect filters to do their jobs.  Bandwidth is often specified as the 3db or 6 db down point.  But filter rolloff continues for quie some time after that.  The further away from the signal you are the better.  For SSB, 3 KHz is pretty bad spacing. 

Then there are the simply large signals...  Sideband suppression and other products may be attenuated by 30 or even 40 db (1,000x to 10,000x).  But when you are sitting right next to a neighbor running full legal limit (it IS a down solar cycle, after all) whose antenna is within 50-300 feet of yours, those products will be very significant, and so will the receiver desense on the same band.  Even if he or she is a really nice person.  I have exactly that situation in the dense urban neighborhood I'm in.  Much of Long Island is similar.


Gone are the days when SSB filtering was done by analog circuits. Today it is almost universally processed by DSP with digital filters with brickwall (-60 dB or better) properties either at IF (most radios) or right at carrier frequency (in direct sampling radios). It does not mater how much microphone is overdriven - input could be a white noise for that matter. Low signal analog circuits do not produce much of IMD to speak about. Thus the only source of IMD TODAY is power amplifier, either one in radio itself, or external linear.

Regarding the location  - those with splatter are rarely local. And I can find a lot of loud (S9+10) signals on the band that do not spill over 3 kHz away.




You can splatter a 1 watt DSP radio with wide open mic gain. Garbage In Garbage Out. Those who splatter are almost never local for their are more hams in the other states combined. On any day, on twenty or forty meters, half of the signals are splattering with many below S9.


Title: RE: Ham Xcvrs' and Amps', Transmit Spectral Purity, IMD Products, vs. comm/maritime
Post by: K6BRN on February 19, 2018, 08:37:02 PM
Tom:

There is nothing ideal about a digital filter, other than it is a filter type implemented to be as mathematically exact as possible.  Common types will be very familiar to analog designers: Butterworth, Chebychev, elliptical, etc.  None of these are "ideal".  And there are a few twists, like IIR vs. FIR structure implementations in the digital world.  All of these types introduce some distortion, none (that are practical) have a vertical, infinite ("brickwall") rolloff.  That's pretty much an amateur's mistaken impression.  Rather they have a well shaped roll-off, often helped by an up-front weighting function, to suppress unwanted responses - like ringing.  And competent designers recognize that digital filter performance is ultimately driven by front-end analog filtering.  If the front-end analog filter leaks an unwanted signal directly into the pass-band, the digital filter has little hope of directly removing it.  Ask Icom about that.  (yes, there are some advanced signal correlation methods - based on known signal of interest characteristics - that can help - but I'm pretty sure you are not talking about those).

And your statement:

Quote
t does not mater how much microphone is overdriven - input could be a white noise for that matter. Low signal analog circuits do not produce much of IMD to speak about. Thus the only source of IMD TODAY is power amplifier, either one in radio itself, or external linear.

... makes it pretty clear you have no idea what you are talking about or what IMD really IS.  In the case of overdriven audio, particulary for FT and JT modes, the audio passband is already many channels wide, so distortion is passed through the IF and RF amplifiers and creates "splatter", without ever needing the amplifier to contribute distortion.

In fact, you're likely one of the problem children on the airwaves who cranks his audio drive and compression hard over - can't make any difference to IMD (per your claim above), and IMD is THE serious problem and not ignorant operators, right?

And you never have problems with nearby operators on the same band - like on field day.  Wow.  I'm impressed.  You do operate, right?



Title: RE: Ham Xcvrs' and Amps', Transmit Spectral Purity, IMD Products, vs. comm/maritime
Post by: AC2RY on February 19, 2018, 09:16:53 PM

... makes it pretty clear you have no idea what you are talking about or what IMD really IS.  In the case of overdriven audio, particulary for FT and JT modes, the audio passband is already many channels wide, so distortion is passed through the IF and RF amplifiers and creates "splatter", without ever needing the amplifier to contribute distortion.

In fact, you're likely one of the problem children on the airwaves who cranks his audio drive and compression hard over - can't make any difference to IMD (per your claim above), and IMD is THE serious problem and not ignorant operators, right?

And you never have problems with nearby operators on the same band - like on field day.  Wow.  I'm impressed.  You do operate, right?



You are confusing two different things: in-band distortion (and IMD3 will be within SSB pass band) and out of band distortion (IMD5 for instance, will be out of band when done common 1kHz wide two tone measurements).

FT8 and other digital modes are transmitted using SSB or even wider pass filter.  This is the problem with overdriving audio chain - analog circuit clips before conversion to digital for processing in radio and DSP has no knowledge that signal has to be 50Hz wide - not 3kHz wide. If FT8 signal will be created inside your radio DSP (like voice SSB is), there will be no out of band (50 Hz wide) emission other than distortion added in high power signal path. For voice - compressor in DSP deals with avoiding clipping and thus there should be no out of band (3kHz) emission even if voice signal is compressed to the limit.





Title: RE: Ham Xcvrs' and Amps', Transmit Spectral Purity, IMD Products, vs. comm/maritime
Post by: KA4WJA on February 19, 2018, 10:48:48 PM
Brian, et al,
Welcome to the discussion! :)

As I wrote the other day:
I suppose that since most never hear themselves on-the-air, and darn few ever hear what their own transmitter does on freqs +/- a few khz (or worse +/- 10 to 20khz), the actual transmit IMD and spectral purity of our signals tend to get over-looked...and that is a shame!
So, I'm glad you've joined in...but why all the talk about filters, and analog vs. digital??

You know, everyone has different experiences in life, and in the amateur radio service (btw, many of us still think of the Amateur Radio Service as a "service" not a "hobby"...but that's a whole 'nother discussion which I won't drift into here. :) ), and as such we all have different opinions and points of view...and, nobody's is more or less valid that another's...
So, I'm sincere when I say welcome!
(and, I took no offense to the inference that anyone that wishes to discuss and learn about transmit IMD and spectral purity is somehow in need "medicine"...actually, it made me laugh!!  especially since you included yourself, by contributing here. :) )

BTW, if you knew me, I'm darn sure in 30 seconds you'd learn how non-obsessed I am about   IMD...:)   (ya' know it's pretty hard to get to know someone by their technical writings...)

And, if you read all of this discussion, you'll see that "too high mic gain" has already been accepted as a major contributor to splatter, and of course the "all knobs to the right"-types causing problems, but what about the remaining 95% of hams on HF SSB, PSK, etc., that adjust / operate their radios correctly, and some (many??) of them are unaware that they are also causing splatter / interference, just by virtue of them using an HF rig with poor transmit IMD specs (and/or the CW ops, with wide signals due to too short rise-time keying, but also poor transmit spectral purity)....what should we do for them?? Ignoring the problem hasn't helped, has it??

Everyone should remember that the issue I started this thread to discuss here, is IMD...and of course this is not controlled by filters, so this discussion is not about filter skirts or roll-offs, 'cuz IMD is not governed by this at all...I know many think it is, but it is not...(now, the "low-end enhanced" ESSB is another issue, but a part of amateur radio that is thankfully fading from our airwaves...and not the focus of this discussion)

Also, please remember that there is no FCC (nor ITU) rule / spec of IMD in the Amateur Radio Service...

Further, I wonder why is it so hard to read the test results of radios and see for yourself that making a clean solid-state HF transmitter (at 100 to 150 watts output) is not expensive...by many accounts it would cost about $25 to $50 more in parts, an extra hour of engineering time to copy already existing circuits that the same manufacturer uses in their other radios, and perhaps an extra 10 to 20 watts of DC power (on transmit)...how in the world is that considered "too expensive" to hams that will drop a quick $1000 (or more) on a rig??  Okay, maybe on a "entry-level" rig that would drive the retail price up from $600 to $700, yep that's a tough nut to advertise...but "too expensive"??  And, who was asking for perfection?? (not me!)

{yes, I know this isn't "global warming" or "election tampering", or even despicable leaders using chemical weapons, nor rogue states threatening nuclear attack, etc...but, I use lots of solar energy on my boat, don't use energy frivolously, I pay attention to political issues, elections, etc. do my homework and vote carefully, and I am horrified by SARIN gas being used openly (and glad my late father didn't live to see this, as he risked his life fighting so nobody would ever suffer this horror again), but poor transmit IMD, etc. is an issue that effects all users of our HF bands, and unfortunately many (most) are actually unaware of what their transmitters are doing...and I don't think that it is beyond the limits of "good engineering" and "good amateur practice" to try to learn more about this and to teach others as well, and truth be told, in MY OPINION, it IS "good engineering" and "good amateur practice" to learn these things and pass on this knowledge to our fellow hams, and not simply repeat false platitudes that sound good 'cuz that's what most are saying!!}

Maybe from the outside it looks weird, but it looked weird to many hams 20 - 25 years ago, when some hams were very frustrated with noisy receiver oscillators, and poor (to non-existent) 1st IF filtering in "modern" rigs, and many of these guys were thought of as "obsessed with receiver IMD", but if it were not for them, we'd all be using receivers like the KWM-380 (anyone ever listen on one, on a busy contest weekend? 'cuz I have, and it was crap!! And, even on a easy weekday, it was crap! BTW, I was considering buying one, way back when, 'til I used it...what a piece of s**t!) or an FT-757 (had a friend that had one connected to a tri-band yagi at 50' and what a crappy rec!), etc...
Maybe if we hams actually take the time to learn and teach each other about transmit IMD and spectral purity, we will see how much better our on-air lives could be, and then we can all vote with our wallets and only buy rigs with good transmitters!!..

BTW, that is what I'm doing....if Apache / ANAN made a rig with knobs (no not a RasberryPi) I'd buy one this spring....
BTW, here is a scan of a printed out (and hand-drawn highlighting of the pre-distortion ON, of the ANAN-8000D)...the test was from  Adam Farson, VA7OJ/AB4OJ..
(http://i65.tinypic.com/50h0f9.jpg)
Sorry about the poor quality image!
The ANAN-8000D's  3rd . 5th / 7th / 9th order IMD
33 / 40 / 54 / 60  (with NO pre-distortion) at 200 watts

67 / 70 / 70 / 70  (with pre-distortion) at 200 watts


And no, Flex is not debuting any pre-distortion rigs this year (and possibly never?)...I'm afraid the IC-7851 is out of my price budget, but the TS-990 is...but even it (or the TS-590SG) isn't clean enough for me....so, I'm stuck with my Icom M-802's (and my old TR-7's)...

What about you?

A quick dozen choices for all of you....Who do you want to operate on SSB, 3 - 6khz away from (or even 10khz to 20khz from) guys with  K3, FT-857D, FT-991, IC-7600, IC-706, TS-590S, etc.,(and what if they're driving an ALS-600??  or a 1.3kFA??)  or a guys with TS-590SG, M-802, 32S-3, TS-830S, IC-765, IC-7851, etc.??  (and maybe these guys are driving a pair of 3cx800's or an 8877??)  Who do you want to operate near??  And, what rig are you using??  

(http://i64.tinypic.com/2daa77m.jpg)

(http://i64.tinypic.com/clwyu.jpg)

Yep, none of us want to operate next to the guy with the mic gain cranked up...but again what about the other 90% to 95%?? (and, just this past week on-the-air, I helped a guy turn down his mic gain, improve his signal immensely, and he thanked me for it....and I told him about eham.net, and he said he'd check it out...)

{yes, assisting our fellow hams to properly adjust their mic gains and keep from over-driving their amps, are great things....but what about the other 90% to 95% of hams, do we just let them buy crappy rigs and just accept the worsening of our on-air situation?}

And, are you all willing to learn, teach, and vote with your wallet??  

Look at the specs of these "modern" radios....their receivers are great, their transmitters are crap!!...the reason their receivers significantly improved, was due to market pressure and competition...

Has it not dawned on some hams that the same guys asking for better receivers over the past few decades have been saying for the past 10 years that the transmitters are crap!! ??  And, these same guys have been saying now, for the past decade, that the limit of our better HF transceivers' receivers, are the transmitters of others on-the-air!! ??   Is this not clear?? (read what is being written and said, and I think you'll see)
Please read this:
https://www.eham.net/ehamforum/smf/index.php/topic,97093.msg1053647.html#msg1053647


Sorry about the rambling....but I've been asked to write more detail about the real-world and what others are doing/saying, rather than "just the facts"....'cuz many are overloaded with info, and just want some easy way to see where the wind is blowing!!

In addition to many on-air discussions about IMD over the years, I've gotten e-mails regarding these discussions here, thanking me for bringing this subject up!
Now, to be clear, I don't CQ looking for someone to rant to about IMD!!  :)  
Not tooting my own horn here, just stating a fact...and showing the difference experiences that I've had...

For explanation...Aside from the obvious that everyone from NC0B and SM5BSZ, to myself, to many HF contesters, etc., have all been saying for the past decade the actual limiting factors in our ham transceivers' receive performance are the other transmitters on-the-air!!  (read just some of the quotes I included this past week)
https://www.eham.net/ehamforum/smf/index.php/topic,97093.msg1053647.html#msg1053647

I myself have been a proponent of clean transmitters and low-IMD for decades now (I was shown and taught about 2-tones IMD tests as a teenager in the 1970's)....but, I'm hesitant to delve too deeply into the "why" I started this discussion here 4 years ago...even though this subject has been important to me for a long time, this particular impetus will drift the discussion a bit, but as long as we don't ramble on about this too much, it's probably okay??
Perhaps I haven't recently made it clear here, but I have actually personally been interfered with on HF (both ham and maritime freqs), by splattering SSB signals many times...

And no, it is not front-end overload!!  (really??) The old TR-7 can take a seriously strong signal before blocking, as can my Icom M-802's....but what I think you might be referring to is RMDR, or maybe 3rd order IM DR?? I know what Reciprocal Mixing is and how it manifests, and I understand the phase-noise limitations of my old TR-7's, but my M-802's do not suffer from these issues...and with some serious 3rd IMDR specs, it takes a band-full of strong signals to cause any  issues....and I do know the difference between what is actually splatter and what are issues caused by receiver's reaction to other signals on-the-air....the main issue that I read on-line and hear on-air, is that most hams do not know these differences, let alone what transmit IMD is!!

In my opinion, If we can all try to learn more, and educate others too, we will all find our on-air lives much happier!

On the ham bands, the splatter I usually hear is from operators that are not well-informed of what transmitter IMD is....and on the maritime freqs, this has been exclusively from others using HF ham rigs on the maritime freqs (and I'm not the only one that experiences this on maritime SSB Voice comms!!)  (in addition to maritime SSB Voice comms, many folks trying to use Sailmail stations, and/or Winlink stations when in various anchorages, find their reception disrupted by other HF users splattering using ham HF rigs)

Here is just one personal example:

Late afternoon, about 5 years ago (a few instances of this, actually spurred my research and was the impetus for me starting this discussion here), I was on 12.359mhz, with two 1Kw SSB stations on 12.362mhz and 12.365mhz (both approx S-5 to S-7), and never heard any artifacts / IMD from them when I was on 12.359mhz, they were only transmitting for about 7 minutes, on a regular schedule top and bottom of the hour, and I use 'em to check propagation....later, after they left the air, a station on 12.353mhz came on, and there was so much splatter on 12.359mhz, that I could no longer copy the weaker stations (mostly vessels sailing across the Atlantic) I was passing traffic for / assisting with weather info, etc., and the offshore weather net closed early that day (and the next day as well, due to the interference from these same folks)...this was a 100-watt station (from another boat, his signal on 12.353mhz was about S-5...found out later he was approx 1000miles from me, running an Yaesu FT-857), he was calling another boat and the other guy was weaker (he was running an IC-706, and was about 700 miles from me).   Understand that maritime channels are 3khz apart, and we were separated by two channels, 6khz....and the splatter from that 100-watt FT-857 was so bad that those running type-certified marine rigs (some of them "down-conversion" rec with excellent 1st IF filters) 6khz away couldn't continue....but, the commercial 1Kw maritime transmissions 3khz and 6khz above us, were not interfering at all!!

Another instance on this same weather net but during a morning sked, found a station on 12.350mhz (a non-standard freq) splattering badly...his signal on 12.350mhz was strong (S-7) but sounded processed and a bit too high mic gain...but his splatter made the morning check-ins 9khz away, difficult...found out later (he told me openly) that he was running an Ameritron ALS-600 amp (he said he was getting 700+ watts out, but I have my doubts as I thought it would soon melt at that power level??), and when I commented that he was flat-topping and severely over-driven, he just said "oh" and changed the subject...

I could go on and on, and highlight experiences on 75m and 40m...and some on 20m (but don't operate there much these days), but I think you see that we have different experiences and the fact that I do openly discuss IMD on-the-air separates us widely, I guess...

{btw, I was asked by some friends to attend the 4th annual TechCon, but don't think I can make it (family issues take priority)...but there is another place that many fellow hams are interested in transmit IMD.}

 
Yep, some splatter on our ham bands is of course mic gain and over-driving amps....and yep, all of this has been well discussed....but again, what about the other 90% to 95% of the hams that are not aware that they may be splattering simply by running their rig as prescribed in the manual??  'Cuz it's these guys that make up a large portion of the splatter that I experience...I would like to say they're the over-whelming majority (which has been my personal experience), but if I write that, all we'll do is argue...so, let's just say that a lot of HF ham SSB transmitters are causing unnecessary splatter / buck-shot / interference to others everyday on-the-air...some might not have this same experience, and I accept that, but please accept that some of us do have these experiences and we do wish to improve things... :)


BTW, discussing baseband bandwidth and filter bandwidths/shapes is a big red herring here, as none of those have any effect on IMD levels....of course the wider the baseband bandwidth, the wider the IMD products are spread (but their levels are not effected), and of course when expanding the baseband lower, this also causes opposite sideband leakage, etc. as well as extra stress / loading of power supplies, which can certainly contribute to IMD levels, but again, not really the focus of this discussion...(and thankfully, these ESSB guys are slowly disappearing from the air)...

But, just for clarification:  From the 1930's to the 1950's, telco "SSB" channels were 4kc's wide....the baseband was 300cyl's to 3400cyl's, with "guard bands" taking up the remainder of the channel...then after the 50's (as I explained in detail above) the baseband was narrowed to 300hz to 3000hz, and with good engineering and clean signals, the standard "SSB" channel was narrowed to 3khz...and this has been the commercial / maritime / aviation "standard" for many decades....the more modern (21st Century) "SSB" channel bandwidth is 2.8khz, with baseband from 300hz to 3100hz, and this is the most recent ITU standard...now, of course not all the emissions are contained inside that 2.8khz....but have you seen the emissions mask??  Here's the older one...(will look for the newer one)....

(http://i68.tinypic.com/2zqsj1h.png)

Those hams that haven't been in commercial / maritime / aviation SSB comms, are usually unaware of these requirements and repeat the "myths" that you can't squeeze in every 3khz....now, the ironic part is that this myth is becoming a self-fulfilling prophesy, as the worse our transmitters get, the wider we'll need to space ourselves out...but with more hams on HF, why not find ways to cause less interference, rather than more??

But, the red herring here is that IMD is NOT controlled by filters, IMD levels are not controlled by the baseband bandwidth....this discussion is not about filter skirts or roll-offs, 'cuz IMD is not governed by this...


Yes, of course, help others (as I do) to turn down their mic gains, and assist them in not over-driving their amps....but why not educate them on what rigs have poor transmit IMD and what rigs are better??

Yes, of course, higher voltage SS PA's have devices that can operate longer in the linear range, and hence less time in crossover/transition, and therefore can theoretically be easier to keep linear (produce a cleaner signal) than lower-voltage SS PA's....but, as can be seen by the actual, real-world, scientific tested results, there are 12vdc PA's that provide better IMD results than their higher-voltage cousins...


I mean, it ain't rocket science here...as I wrote to one of best friends this weekend:
Quote
"...in the maritime service, for the past 40-50 years, the cheap and dirty way is to choose devices (bipolar for 12 volt PA's or FET's for higher voltage PA's) for a 300watt PA, BUT...
But design and build a 150 watt PA using those transistors....meaning especially design the output matching section for 150 watts, NOT for the device's 250-300 watt typical design use, and tune/bias the PA properly in Class AB or Class B (run the pre-driver in Class A), making sure whatever load changes that occur at lower than nominal voltages (battery voltages are not "13.8vdc" on a boat) are compensated for....and you've got a clean 150 watt transmitter that will still be clean with 11.5vdc at the back of the rig...(ever heard an IC-706 on a battery??)
Like I said, not rocket science!  Not very expensive, either! (probably would add $50 to the cost of an HF rig!)

Although Kenwood, Yaesu/Vertex, and SGC left the maritime market in late 90's / early 2000's, Icom, JRC, Furuno, Cohban/Thrane&Thrane/Skanti, and SEA are still alive and well making marine HF rigs (but in 2017 Furuno has discontinued their 12vdc rig, designed for the small-boat market...and their newer rigs are all 24vdc, which is the nominal battery voltage on ships..)

With modern 12vdc Icom marine radios, like the M-802 at 150watts out having IMD products of - 47 / -50 / -58 / -60  (and even a little better at 100watts)
And, heck less than 20 years ago, the JRC JST-245 ham rig at 150watts out had IMD products of -39 / -56 / -58 / -60...
And, just 20 - 25 years ago, the Icom IC-765 ham rig had IMD products of -40 / -45 / -48 / -50...

Why do hams now accept 10db to 20db worse IMD for our current radios? (most of them costing many times the cost of the marine radios)"


Okay, enough of my rambling for tonight...

Do hope I helped clarify things??

73,

John,  KA4WJA



Title: RE: Ham Xcvrs' and Amps', Transmit Spectral Purity, IMD Products, vs. comm/maritime
Post by: KM3F on February 20, 2018, 12:17:37 PM
Hi John,
This is my  first reply since 2014 when I mentioned the predistortion being workled on and now has come to market 4 years later.
We talk about this but no one offers any detail about how to accomplish it.
What is different about your M-802 radio that offers lower IMD?
In my opinion, predistortion method while fine because it seems to work, is just covering up the problem in the radio it's used on.
Granted, in a radio, IMD is a different source than an external amplifer producing it.
Question is, is the radio producing it and being amplified.
Seem to me that if predistortion can greatly help by feeding back a sampling, is the radio is producing it to begin with and amplifier raising the amplitude and adding to it.
We need to know these things.
.
On a side point, back in the mid nineties a compandored system was developed to fit dozins of channels with in a 3  kHz bandwidth.
The receiver  audio sounded monotone from lack of band width and the RF amplifer in the transmiter was very linear.  I have one of those 'amplifier's' running on the 222 band in a home built all mode transmitter. The transfer curve as measured with Ham grade equipment is as straight as I have ever saw an amplifer up to the point of nosing over from near instant compression at the limit. The amplifer is 26 volt FET push pull and powered from a mate switching supply from the same company.
.

Good discussion here.

KM3F





Title: RE: Ham Xcvrs' and Amps', Transmit Spectral Purity, IMD Products, vs. comm/maritime
Post by: K6BRN on February 20, 2018, 12:31:16 PM
John:

You have definitely  made the longest post that I've ever seen on this forum!  Like your graphics.

To answer some of your questions...

I did not start the digital vs. analog filter debate - AC2RY did,  And he is frankly out to lunch and not coming back any time soon on this topic.  My point was that digital signal processing is not "perfect", rather the processing functions are "Ideally predictable".   AC seems to believe in "brick wall" filters with infinite rejection and shape factor.  And that analog front end filtering makes no differenence to a DSP design.  Not happening any time soon in any practical or usable design.

Second, I simply disagree that IMD is a serious problem caused by mainstream radio and high power RF design in the amateur radio segment.  That has not been my experience.  When I have seen problems, its been due to mistuned tube amps, poorly constructed "DIY" solid state amps with zero filtering and a variety of other operator errors that many interpret as IMD ("splatter").  IMD is there, but I've not experienced it as a significant problem outside of obvious amateur goofs.  Nonetheless I respect your opinion and different perspective.  You may have a different set of experiences we can discuss rationally.

I've also had to design DSP comms systems with severe IMD, PIMs and broadband linearity requirements, so this is not new to me.  And I understand the compromises that need to be made to optimize each.  Admittedly on very different systems than amateur radio equipment.

And with that, lunch is over and I'm off to a design review.

Best Regards,

Brian - K6BRN






Title: RE: Ham Xcvrs' and Amps', Transmit Spectral Purity, IMD Products, vs. comm/maritime
Post by: KB2TIS on February 20, 2018, 05:40:16 PM
With modern 12vdc Icom marine radios, like the M-802 at 150watts out having IMD products of - 47 / -50 / -58 / -60  (and even a little better at 100watts)

-47.. In what mode? The SSB plots in the (2002) test report have a worst case around -30. In AM the plots look nice, but the current product page at Icom USA says AM is RX only. I guess you don't have to refile when the product loses functionality?


Title: RE: Ham Xcvrs' and Amps', Transmit Spectral Purity, IMD Products, vs. comm/maritime
Post by: KA4WJA on February 20, 2018, 05:45:04 PM
Brian,
12mhz, USB..(closest to a 20 meter ham band spec that I have)
Did you not see the analyzer scan?

(http://i67.tinypic.com/30u6cfd.jpg)


73,
John,  KA4WJA


Title: RE: Ham Xcvrs' and Amps', Transmit Spectral Purity, IMD Products, vs. comm/maritime
Post by: KB2TIS on February 20, 2018, 07:40:06 PM
Brian,
12mhz, USB..(closest to a 20 meter ham band spec that I have)
Did you not see the analyzer scan?

Looks like 40 or so.

And at 2MHz, it is more like 30.

I won't ask why the mask seems to be drawn differently for all the occupied bandwidth plots, sometimes asymmetrically - and the signals are not centered in the mask. Of course, I don't have an HP8564E to find out for myself how much fun it is to set up a test like this..


Title: RE: Ham Xcvrs' and Amps', Transmit Spectral Purity, IMD Products, vs. comm/maritime
Post by: AC2RY on February 20, 2018, 07:45:10 PM


I did not start the digital vs. analog filter debate - AC2RY did,  And he is frankly out to lunch and not coming back any time soon on this topic.  My point was that digital signal processing is not "perfect", rather the processing functions are "Ideally predictable".   AC seems to believe in "brick wall" filters with infinite rejection and shape factor.  And that analog front end filtering makes no differenence to a DSP design.  Not happening any time soon in any practical or usable design.


People here should understand the difference between IMD caused by compression or clipping of audio signal and non-linearity of RF chain. Before signal goes into RF amplifier it can be processes digitally, and unlike your believe in "impossibility" of brick wall filters, they do exist. You use one every day when you play music from CDs. There filter goes from pass band (+- 0.1 dB ripple) to full rejection (-80 dB or more of attenuation) in a narrow band between 21 and 22 kHz. The same can be easily done (and is done) by DSP at IF frequency in radio. You do not need too much of processing power for that. Only after signal is up-converted to carrier frequency real problem with IMD begins, as there is no easy way to correct non-linearity, other than use pre-distortion.




Title: RE: Ham Xcvrs' and Amps', Transmit Spectral Purity, IMD Products, vs. comm/maritime
Post by: SM0AOM on February 21, 2018, 06:22:36 AM
As a designer of commercial (air/ground) and military HF networks, my
comment is that amateur radio has created this problem for itself.

There are no channel rasters and frequency planning, coupled to the absence of any IMD suppression requirement.
In amateur radio, there are common instances of extreme dynamic range requirements, with no control at all of frequency spacing.

Commercial users have made quite extensive spectrum planning to reduce the actual dynamic range requirements, as an example the frequency allotment plan for the Aeronautical (R) HF/SSB services prescribes that no adjacent channels used in the same geographical area are less than 6 kHz, most often 9 kHz apart.

Further, the antenna patterns and power levels for a given coverage area are chosen so that the adjacent channel dynamic range requirements only in exceptional cases exceed 50 dB.

Nevertheless, there are quite stringent requirements for IMD suppression in fixed transmitters, the newest generation provide about -50/55 dB down in the first +/- 3 kHz adjacent channels with speech signals.

Japan Radio (JRC), Rohde&Schwarz and Krupp-Atlas build DSP-based solid-state transmitters having this level of performance, the JRC JRS-900 series comes to my mind.

Put in perspective, the current state-of-the-art for "average" amateur transmitters is such that any receiver on the top 2/3 of the Sherwood list would be perfectly adequate with respect to the close-in performance.

Some receivers are better with respect to blocking at larger frequency spacings.

A very fundamental limit to the first adjacent channel dynamic range in realisable transmitters exist, which is derived from the noise and distorsion properties of any D/A and amplifier parts in the signal chain.

Currently, it is difficult to exceed about -90 dB even if perfect linear amplifiers would exist.

Finally, something that is sorely missed is a "Sherwood list" for transmitters.





Title: RE: Ham Xcvrs' and Amps', Transmit Spectral Purity, IMD Products, vs. comm/maritime
Post by: KA4WJA on February 21, 2018, 05:59:32 PM
Ken and Karl-Arne,
Welcome!

I'm going to be brief here (a welcome change, huh?)

FYI, to everyone!!
It was not / is not my intention that hams use marine transceivers and certainly not the top-drawer commercial units from Rohde & Schwarz, etc...
Rather I used the Icom M-802 as an example of a reasonably-priced 12vdc IF-DSP HF rig, that has 10db to 20db better transmit IMD than most of our ham rigs. (and this is a radio I use often)



1)  Brian, I'm not a professional RF design engineer (physics major), but have been working in RF most of my life, own my own electronics firm, an offshore sailor, HF user, etc. etc. etc...
So, I will give you my take, not an absolute.  :)

As I wrote yesterday:
Quote
...in the maritime service, for the past 40-50 years, the cheap and dirty way is to choose devices (bipolar for 12 volt PA's or FET's for higher voltage PA's) for a 300watt PA, BUT...
But design and build a 150 watt PA using those transistors....meaning especially design the output matching section for 150 watts, NOT for the device's 250-300 watt typical design use, and tune/bias the PA properly in Class AB or Class B (run the pre-driver in Class A), making sure whatever load changes that occur at lower than nominal voltages (battery voltages are not "13.8vdc" on a boat) are compensated for....and you've got a clean 150 watt transmitter that will still be clean with 11.5vdc at the back of the rig...(ever heard an IC-706 on a battery??)
Like I said, not rocket science!  Not very expensive, either! (probably would add $50 to the cost of an HF rig!)


Although Kenwood, Yaesu/Vertex, and SGC left the maritime market in late 90's / early 2000's, Icom, JRC, Furuno, Cohban/Thrane&Thrane/Skanti, and SEA are still alive and well making marine HF rigs (but in 2017 Furuno has discontinued their 12vdc rig, designed for the small-boat market...and their newer rigs are all 24vdc, which is the nominal battery voltage on ships..)

With modern 12vdc Icom marine radios, like the M-802 at 150watts out having IMD products of - 47 / -50 / -58 / -60  (and even a little better at 100watts)
And, heck less than 20 years ago, the JRC JST-245 ham rig at 150watts out had IMD products of -39 / -56 / -58 / -60...
And, just 20 - 25 years ago, the Icom IC-765 ham rig had IMD products of -40 / -45 / -48 / -50...

Why do hams now accept 10db to 20db worse IMD for our current radios? (most of them costing many times the cost of the marine radios)"

A cursory look at recent Icom HF marine rigs (like the M-802), shows that this is what they have done... the cheap and dirty way is to choose devices (bipolar for 12 volt PA's or FET's for higher voltage PA's) for a 300watt PA.
But they design and build a 150 watt PA using those transistors....meaning especially design the output matching section for 150 watts, NOT for the device's 250-300 watt typical design use, and tune/bias the PA properly in Class AB or Class B (run the pre-driver in Class A), making sure whatever load changes that occur at lower than nominal voltages (battery voltages are not "13.8vdc" on a boat) are compensated for....and you've got a clean 150 watt transmitter that will still be clean with 11.5vdc at the back of the rig...

BTW, although the worldwide market for maritime HF radio is small compared to ham radio, Icom holds a significant market share of the offshore pleasure boat HF communications (although not a legal requirement to carry, most do)...the M-802 alone is on-board as many as 2/3's of these boats, and if you include the older M-700Pro and the M-710 that are still working, Icom's market share is almost 95% (figures from the SSCA and OCC)....and these are all 12vdc battery powered radios...

The big players on the commercial shipping vessels (what we call SOLAS vessels) where they must comply with strict GMDSS rules are Furuno, JRC, Sailor/Thrane/Skanti/Cohban, etc. and some others making comms gear for the shore stations...(as well as Rohde&Schwarz ??)

Again, not my intention that we hams go out and buy marine radios!
Just that the same manufacture that makes the M-802, also makes the more expensive IC-7600...and maybe we hams should ask 'em why can't they actually provide us with radios with better transmit IMD levels / better PA's??

 

2)  Karl-Arne, I know from the shore station perspective the channel spacing is more than adequate (and as there are few HF SSB Voice shore stations anymore, but still many MF), and for the SOLAS vessel comms, HF is secondary to Satcom for most, except for DSC signaling, so there are few professional / commercial maritime users who find interference from each other...but.
But, in the world of pleasure boat maritime HF comms, it is an issue with some using modiified ham rigs... :)

Somewhere in a sailing magazine (about 10 years ago?) there is a picture of one of Rohde & Schwarz company principles (son of founder?? or President??) on his sailboat, in front of a nice rack of Rohde & Schwarz HF equipment!!  What a sweet set-up!

But, fyi, as far as I know almost all commercial shore station and SOLAS/GMDSS certified HF transceivers are 24vdc-28vdc / 110vac-230vac transceivers...including the R&S 2000 series...
But, most pleasure boats are 12vdc, with most using solar/wind for most of their charging....and while I do have it, most do not have 110vac - 230vac power, except for inverter power as needed for intermittent use...


FYI, most (non-SOLAS) HF maritime set-ups are very modest (like most ham shacks on shore)...here are some pics of mine...
(http://i65.tinypic.com/16bk075.jpg)

(http://i65.tinypic.com/3129xs9.jpg)


Oh, and an old pic of ham shack at home (I've added some things since then, including an M-802, but still use my TR-7's..)

(http://i66.tinypic.com/2chx9x4.jpg)



Hope you don't mind the brevity tonight?

73,
John,  KA4WJA
 


Title: RE: Ham Xcvrs' and Amps', Transmit Spectral Purity, IMD Products, vs. comm/maritime
Post by: KA4WJA on February 21, 2018, 06:16:57 PM
Brian, KB2TIS,
As I have written before, it is not and was not my intention that hams use marine transceivers!!  :)
And, of course, not the Icom M-802...
Rather I used the Icom M-802 as an example of a reasonably-priced 12vdc IF-DSP HF rig, that has 10db to 20db better transmit IMD than most of our ham rigs. (I own two of them, and this is a radio I use often)

I got these scans from a friend at an EMC/RF compliance testing lab, who got 'em from the FCC, from the part 80, part 87, and 90 applications...
(actually got only this one on this laptop)

I've made a quick drawing on it for clarification...forgive my finger painting! :)
12mhz, USB..(closest to a 20 meter ham band spec that I have)

(http://i65.tinypic.com/1zzgmxt.png)

By my eye, I see  3rd/5th/7th/9th order IMD products at:
-47db(PEP) / -50db(PEP) / -58db(PEP) / -60db(PEP)


Have a look at the test results of the ham rigs, 'cuz that's the point of this discussion.. :)

Hope this clarifies...

73,
John,  KA4WJA




Title: RE: Ham Xcvrs' and Amps', Transmit Spectral Purity, IMD Products, vs. comm/maritime
Post by: SM0AOM on February 22, 2018, 12:37:31 AM
I have some comments.

First, a blunt fact is that the engineering knowledge among the "average amateur" is sadly lacking, and it is nowhere in parity to our vast freedoms and privileges.

If we make a comparison to our "commercial brethren", we have lower knowledge standards, while they are not allowed to operate anything else than type-approved equipment having a minimum of operating controls.

Secondly, the marketers at the amateur radio manufacturers have sacrificed fundamental transmitter distorsion properties in exchange to "punchy audio" and "lively ALC indications".

The "instant hams" of today have absolutely no clue of what IM distorsion and adjacent channel suppression actually means, and the vast majority of them would not care even if they knew.

This is a fundamental problem, which only can be solved by
1) Increasing the difficulty of the tests;
2) Reducing the power limits;
3) Limit the use by unqualified operators to low-power type-accepted and channelised equipment




Title: RE: Ham Xcvrs' and Amps', Transmit Spectral Purity, IMD Products, vs. comm/maritime
Post by: AC2RY on February 22, 2018, 05:24:57 AM

This is a fundamental problem, which only can be solved by
1) Increasing the difficulty of the tests;
2) Reducing the power limits;
3) Limit the use by unqualified operators to low-power type-accepted and channelised equipment


Yesterday I had over the air chat with a fellow on 160M in AM mode. His signal (from 300 miles away) was S9+20 dB and 20 kHz wide. He said that it was DIY amplifier (tubes of cause). When in the end I commented that his signal is too wide, he didn't bother to respond.


Title: RE: Ham Xcvrs' and Amps', Transmit Spectral Purity, IMD Products, vs. comm/maritime
Post by: K6BRN on February 22, 2018, 01:19:27 PM
Gentlemen:

This is amateur radio, which means that no substantial knowledge of communications technology is required in operators and that very experimental, home (and often poorly) designed and built equipment may be assembled, built and used by just about anyone.  AC2RY's previous example is a case in point.  The amaterur radio exams are of nusiance value only and since they come as multiple choice, published answer tests, serve only to block the most ADD affected from being licensed.

In return, we (a broad swath of people and skill mixes) gain quite a bit of freedom to operate and experiment within our very meager uncrowded allocated bandwidths.  And regulation is not overly strict.  Nor are our bands very crowded, except on the currently very popular FT and JT mode segments... or during major contests.  This is actually a GOOD thing.

So in view of this ployglot, pretty sparcely populated and somewhat inherently chaotic environment, how is it again that IMD produced by properly operated radios and amps from major suppliers is a real crisis?  Especially compared to the junk produced by poorly built and/or operated equipment?  Please do not tell me that IMD is completely unregulated.  Requirements, in particular spurious emissions requirements, overlap with IMD performance requirements.  So IMD is not unregulated.  It may not be preceisely regulated to the very low level you desire and specified in the way you like.  But the more regulation received, the less freedom granted.  How much regulation do you really want (where are the condo owners right now - they can comment a bit on tight restrictions and the frustration they cause.)

Regarding the cost of improving IMD performance on TX... one post above remarks that it would only cost a few hundred dollers per amp or radio to do so, and just 20-30% in efficiency (do the math).  Really?  This is insignificant to a ham community that advocates building dummy loads out of beer cans because he cost of a real load, even used, is just too much to bear?  Wow.  Also, cost scales with HOW MUCH improvement is desired,  So... how much do we need, why, and where is the example design to show how this will be done and how much it will cost (labor and materials, please)?

Not that improvement is not possible - it is VERY possible.  But the amateur community has ALREADY voted on this topic with its cumulative wallet.  And the answer seems to be that what we've got is OK for the vast majority of users.  The FCC seems to agree.

So... maybe we should go back to obsessing about air and water pollution (real concerns) and about secret chocolate chip cookie recipies (fun concerns).  It's really more productive.



Title: RE: Ham Xcvrs' and Amps', Transmit Spectral Purity, IMD Products, vs. comm/maritime
Post by: SM0AOM on February 23, 2018, 04:39:24 AM
IMD is not itself specified as a special parameter or spectrum mask for amateur gear, but it can be said that
if you are operating near a band edge so splatter sidebands extend outside of the band edge, you are technically in violation, by allowing the occupied bandwidth to extend into the spectrum allocated for another user.

However, it would be nice if the 1960s/70s practice of regarding a clean transmitter spectrum as a matter of honour would return.

If we look at our privileges in comparision to the actual competence of the average amateur, it quickly turns out they are severely mis-matched, and maybe the Authorities may find this out and reduce the privileges.

Actually this is probably going to happen here, as our regulator, after looking at the competence levels, has proposed substantially reduced power levels.

A special permit which could be awarded after site, equipment and competence evaluation would be needed for operation using the previously permitted power limits.

Lower power operations are beneficial in many ways, from both EMI, EMF and QRM perspectives.
They also encourage the use of Morse which is character building (pun intended).



Title: RE: Ham Xcvrs' and Amps', Transmit Spectral Purity, IMD Products, vs. comm/maritime
Post by: KA4WJA on February 23, 2018, 05:04:50 AM
Brian, K6BRN,  et al,

--- In my opinion, it's not a crisis, but is a problem for many....and it is not "good engineering" nor "good amateur practice"... :(

--- Fact...It's not expensive to do....maybe $25 to $50 extra in parts....and some manufacturers have these better IMD performing HF PA's circuits at the ready (with Icom having them in production right now), but do not put them in their ham rigs...this might increase the end retail price of the basic-entry-level HF rig by up to $100 (probably less)....and probably have no effect at all on the price of the higher-end rigs....(In my opinion, an IC-718 would cost you $75 more, an IC-7300 maybe $25 more, but not much impact in the high-end units...)

--- Fact...obtaining better transmit IMD does not require low-efficiency PA's...nor exotic/expensive hi-voltage FET's, nor is "pre-distortion" necessary to accomplish this...(pre-distortion is great!!, but not necessary)

--- Fact...I started this thread almost 4 years ago, primarily to:

a)  to highlight the above issues...

b)  show my fellow hams the actual IMD products of some of our radios...and remind them to be mindful of the unintentional interference our signals can cause...(whether a mas-produced ham rig, a home-brewed radio, or some commercial/marine rig)

c)  encourage my fellow hams to "vote-with-their-wallets" and only buy radios whose transmit IMD at least compare to what we used to have, and/or whose transmitters meet a reasonably obtainable IMD and spectral purity spec (just like the make for marine transceivers)



1)  The other day you made your opinion quite clear that you do not see transmit IMD as an important issue...and I responded that in my opinion this is not a crisis, but is an often overlooked and rarely understood issue, that does effect many hams...remember I wrote:
Quote
{yes, I know this isn't "global warming" or "election tampering", or even despicable leaders using chemical weapons...
<snip>
....but poor transmit IMD, etc. is an issue that effects all users of our HF bands, and unfortunately many (most) are actually unaware of what their transmitters are doing...and I don't think that it is beyond the limits of "good engineering" and "good amateur practice" to try to learn more about this and to teach others as well, and truth be told, in MY OPINION, it IS "good engineering" and "good amateur practice" to learn these things and pass on this knowledge to our fellow hams, and not simply repeat false platitudes that sound good 'cuz that's what most are saying!!}
I do not wish to drift this discussion off onto tangents....but, where have I written, or implied, that I thought this was a crisis??



2)  Further, I think you may have missed the point of this thread entirely....and that's not entirely your fault, but mine as well for rambling on...

So, to be brief...the point is:
Much better transmit IMD is achievable in our HF radios, and it is NOT expensive!!  (The few homebrew designs that I've heard on-the-air in recent years, have actually not been an issue to me...but, homebrewer's can use these circuits and design ideas to their advantage)... Unless someone wishes to redesign the wheel, the added cost to the average HF ham rig would be about $25 - $50....and some manufacturers already have these designs in actual production!  (have a look at the PA circuits of the Icom M-802, or the M-700Pro, M-710, and/or the JRC radios, etc...and you will quickly see that 10db to 20db better IMD levels can be easily and inexpensively achieved, and has been discussed right here...I'm not posting propriety info / copywrited material here, but you can find their schematics on-line, and you can see for yourself...)


3)  As for efficiencies....I think you misread what I wrote....some of the better HF transmitters have a slightly higher quiescent current....are biased for better linearity....and some have their pre-driver operated in Class A....these MAY increase the DC input power required by about 10 watts to 20 watts...(so as an example, a 100-watt transceiver may draw 21 to 22 amps peak versus 20 to 21 amps peak, at 12-14vdc)...
Where did you read that efficiencies would be 20% to 30%??  'Cuz that is not so...{fyi, most marine transceivers are "150-watt output" 100% duty-cycle, so if looking at their current draw, be aware that you can easily estimate about 70% of that current being needed for "100-watt output" radio}



4)   Directly to some of your other points / queries....

a)  I do not want any further regulations, and have specifically stated that many times!!

You wrote that there are FCC regs for IMD in the amateur radio service??   FCC part 97, IMD regs??   I'm not aware of any of these...
[To be blunt about it....IMD specs / rules / regulations for the amateur radio service, do NOT exist in the US (FCC) nor are their international amateur radio service specs / rules / regulations (ITU)...]

The operator of course is responsible for meeting all bandwidth and emission regs, but there are no IMD specs that the radios need to meet, nor any IMD regs that the operator must adhere to....(if the "spurious emission" spec of -43db applied to IMD products, except for the pre-distortion enabled rigs from Apache Labs / ANAN, and the couple Yaesu rigs if operated in Class A, there are NO amateur rigs that could meet that spec, and 99.9999% of hams would be in violation of that rule every time they transmitted!  So, it's obvious that even though the exact words of the regs might lead you to believe that IMD products are "spurious emissions", according to the FCC they are not considered as such...)

(actually the ITU did propose and pass specific IMD regs in the past 5-10 years, but the manufacturers argued hard against it, and the amateur radio service was exempted...)

The FCC doesn't even have any specific "occupied bandwidth" reg, except that your transmission shouldn't be wider than necessary to communicate the information using that mode of transmission, and that HF voice comms (below 29mhz, I believe) should not be wider than a double-sideband, full-carrier transmission (assumed by most to be 6khz wide)...refer to Part 97.307....as weird as it sounds an amateur HF SSB signal can be 6khz wide (down -26 at 6khz), and still meet Part 97.307 regs!

Please do not tell me that IMD is completely unregulated.  Requirements, in particular spurious emissions requirements, overlap with IMD performance requirements.  So IMD is not unregulated.  It may not be preceisely regulated to the very low level you desire and specified in the way you like.  But the more regulation received, the less freedom granted.  How much regulation do you really want (where are the condo owners right now - they can comment a bit on tight restrictions and the frustration they cause.)

I do not want any gov't regulation here, and have not stated that I do!!  I want my fellow hams to learn what their transmitters are doing, and demand that the manufacturers improve their transmitters!!  ('cuz, as weird as it sounds, the transmitters on-the-air are the limiting factor in our receivers these days!!)

From Part 97.3
Quote
"(8) Bandwidth. The width of a frequency band outside of which the mean power of the transmitted signal is attenuated at least 26 dB below the mean power of the transmitted signal within the band."

"(43) Spurious emission. An emission, or frequencies outside the necessary bandwidth of a transmission, the level of which may be reduced without affecting the information being transmitted."


From Part 97.307

Quote
"§97.307   Emission standards.

(a) No amateur station transmission shall occupy more bandwidth than necessary for the information rate and emission type being transmitted, in accordance with good amateur practice.

(b) Emissions resulting from modulation must be confined to the band or segment available to the control operator. Emissions outside the necessary bandwidth must not cause splatter or keyclick interference to operations on adjacent frequencies.

(c) All spurious emissions from a station transmitter must be reduced to the greatest extent practicable. If any spurious emission, including chassis or power line radiation, causes harmful interference to the reception of another radio station, the licensee of the interfering amateur station is required to take steps to eliminate the interference, in accordance with good engineering practice.

(d) For transmitters installed after January 1, 2003, the mean power of any spurious emission from a station transmitter or external RF power amplifier transmitting on a frequency below 30 MHz must be at least 43 dB below the mean power of the fundamental emission. For transmitters installed on or before January 1, 2003, the mean power of any spurious emission from a station transmitter or external RF power amplifier transmitting on a frequency below 30 MHz must not exceed 50 mW and must be at least 40 dB below the mean power of the fundamental emission. For a transmitter of mean power less than 5 W installed on or before January 1, 2003, the attenuation must be at least 30 dB. A transmitter built before April 15, 1977, or first marketed before January 1, 1978, is exempt from this requirement.

(e) The mean power of any spurious emission from a station transmitter or external RF power amplifier transmitting on a frequency between 30-225 MHz must be at least 60 dB below the mean power of the fundamental. For a transmitter having a mean power of 25 W or less, the mean power of any spurious emission supplied to the antenna transmission line must not exceed 25 µW and must be at least 40 dB below the mean power of the fundamental emission, but need not be reduced below the power of 10 µW. A transmitter built before April 15, 1977, or first marketed before January 1, 1978, is exempt from this requirement.

(f) The following standards and limitations apply to transmissions on the frequencies specified in §97.305(c) of this part.

(1) No angle-modulated emission may have a modulation index greater than 1 at the highest modulation frequency.

(2) No non-phone emission shall exceed the bandwidth of a communications quality phone emission of the same modulation type. The total bandwidth of an independent sideband emission (having B as the first symbol), or a multiplexed image and phone emission, shall not exceed that of a communications quality A3E emission.

..........

14) In the 60 m band:

(i) A station may transmit only phone, RTTY, data, and CW emissions using the emission designators and any additional restrictions that are specified in the table below (except that the use of a narrower necessary bandwidth is permitted):

60 M Band Emission Requirements
Emission type    Emission designator    Restricted to:
Phone    2K80J3E    Upper sideband transmissions (USB).
Data    2K80J2D    USB (for example, PACTOR-III).
RTTY    60H0J2B    USB (for example, PSK31).
CW    150HA1A    Morse telegraphy by means of on-off keying.

(ii) The following requirements also apply:

(A) When transmitting the phone, RTTY, and data emissions, the suppressed carrier frequency may be set as specified in §97.303(h).

(B) The control operator of a station transmitting data or RTTY emissions must exercise care to limit the length of transmission so as to avoid causing harmful interference to United States Government stations.

[54 FR 25857, June 20, 1989; 54 FR 30823, July 24, 1989, as amended at 54 FR 39537, Sept. 27, 1989; 60 FR 15688, Mar. 27, 1995; 65 FR 6550, Feb. 10, 2000; 69 FR 24997, May 5, 2004; 77 FR 5412, Feb. 3, 2012; 79 FR 35291, June 20, 2014]"


b)  I cannot speak for everyone, but perhaps you missed the part where I desired IMD specs like we used to have, and/or we have in modest-priced marine transceivers...
Also, cost scales with HOW MUCH improvement is desired,  So... how much do we need, why, and where is the example design to show how this will be done and how much it will cost (labor and materials, please)?
 Please have a look at this post from this very thread (from 3.5 years ago):

https://www.eham.net/ehamforum/smf/index.php/topic,97093.msg786739.html#msg786739

To be brief, (plus or minus a few db) I'd like to see amateur radio manufacturers to produce radios that attain IMD figures of approx::

3rd = -40 to -45db(PEP)

5th = -50 to -55db(PEP)

7th = -55 to -60db(PEP)

9th  =< -60db(PEP)


Or, keep the 3rd order at better than -42db(PEP) [-36dbc], and meet the Part 80 emissions mask...


I mean how great would it be for a manufacturer to advertise their transmit linearity and state that they "meet the stringent Part 80 commercial maritime specs"  (although they are not that stringent, they would play it up in the adverts!)


 


c)  Brian, I wonder if 20 - 30 years ago, you were also saying this about receiver performance??

Not that improvement is not possible - it is VERY possible.  But the amateur community has ALREADY voted on this topic with its cumulative wallet.  And the answer seems to be that what we've got is OK for the vast majority of users.  The FCC seems to agree.


Yep, 20 - 30 years ago,  "the amateur community" was buying radios with crappy receivers, but there were some hams that were encouraging improvements....and today we not only have low-phase-noise rigs with RpMixDR (and IMD3 DR) that are 30db+ better, but also many manufacturers competing with each other / advertising these specs/features!!!

And, now these same hams (and some others) are now encouraging improvements in transmit IMD....especially since the transmitters got worse at about the same pace that the receivers got better....And, for the past 5 to 10 years, these parallel issues resulted in the limiting factor of the better amateur HF transceivers' receivers are not the receiver, but rather the transmitters on-the-air!!
(have a read of what Rob Sherwood and others have been saying now for years??)

Two issues here:

--- Many hams do not have a clear understanding of IMD, nor exactly how their transmitters work / what they do in regards to off-channel (outside the passband of their filters) interference...

--- Hams will "vote-with-their-wallets", they will buy cheap, etc....but what if they had options??  Many will actually "buy better", if given a choice...



Please understand that I'm not arguing a point, just clarifying things here.

73,

John,  KA4WJA

P.S.  Brian, I've noticed you trolling other discussions here on eham in the recent past (such as the IC-7610 discussion) where you seem to belittle others desire for improvements, by making comments about how we should all be more worried about important things such as global warming, etc.
Speaking just for myself, this does not offend me at all, but it does show that you might want to take your own advice....
73, my friend. :)


Title: RE: Ham Xcvrs' and Amps', Transmit Spectral Purity, IMD Products, vs. comm/maritime
Post by: DL8OV on February 23, 2018, 07:04:14 AM
My turn to dive in again, deep breath  :)

It's right that putting out a clean signal is a matter of honor and I would rather transmit a clean 50W than 100W with unwanted products only a few dB down. In my case I don't buy, I build, and I have spent hundreds of hours building the cleanest TX chain I can. Everything from the microphone amplifier to the finals is optimized for a clean signal rather than low power consumption or large amounts of power out and I'm now reasonably happy with what I have. Time and technology do not however stand still and once a month I still do a quick IMD check on the spectrum analyzer then post a screenshot of the results in the logbook.

Some other points:

The comparison with marine transceivers is an interesting one and after reading the comments here the owners of Elecraft went out and purchased an Icom marine rig. They found that there wasn't much difference in the quality of output between a marine and a ham unit. Last year at Friedrichshafen I discussed this result with Wayne N6KR and he cannot understand why marine transceivers are held in such high regard.

Whilst I admire the dedication of Zenki in his quest for clean transmitters he is a man of mystery. So far I have sent three PMs to him offering to work with him in producing the ultimate clean TX chain and I have never received a reply.

All Knobs To The Right along with trying to get the needle to 100W on a non-peak reading power meter are all a matter of training. If ham radio operators cannot or will not get this training then the manufacturers need to add more functionality to transceivers such as removing the microphone gain control and making all power meters peak reading. Yep, we need idiot proof transceivers, and that's sad.

Finally.........

Look carefully at the work done by the semiconductor manufacturers such as Texas Instruments and Analog Devices when it comes to devices for cable TV. These guys are SERIOUS about linearity and get at least 10dB better IMD from their amplifiers than we see on ham radio gear.

Peter DL8OV


Title: RE: Ham Xcvrs' and Amps', Transmit Spectral Purity, IMD Products, vs. comm/maritime
Post by: K6BRN on February 23, 2018, 12:28:20 PM
John (KA4WJA):

I'm fine with your goals and opinions, and respect them.  I just don't think you are going to get there for the reasons I've outlined.  For example, you state that you started this IMD thread 4 years ago to encourage hams to "vote with their wallets".  They apparently have, but it seems the vote did not go your way.  And many of the items you state as facts are in reality opinions and speculation.  Manufacturers and regulators tend to notice things like that - it weakens your argument... just some friendly advice.

Note that I never said the FCC directly regulated IMD.  I did say their other reqiurements imposed on radios and amps indirectly cover IMD and sets a limit for what they think is acceptable in signal quality.  I also stated my opinion that the relatively light regulation and testing we have already provides us more freedom to experiment and a wider diversity to the community of operators.  Which I LIKE.  Plenty of exclusive clubs for me to join... I prefer the inclusive ones, which amateur radio is.

You certainly do have a lot of time for incredibly lengthy posts and I do appreciate the thought that goes into them.  But more bite-sized comments are a bit easier to digest, especially when some of us only get quick moments to read and respond.

In any case, battle on, John, if you believe in the cause ...

"To fight for the right without question or pause
To march into Hell for a Heavenly cause"

From "The Impossible Dream", Musical: "Man of La Mancha.  One of my favorites.

Brian - K6BRN


Title: RE: Ham Xcvrs' and Amps', Transmit Spectral Purity, IMD Products, vs. comm/maritime
Post by: KA4WJA on February 23, 2018, 03:17:15 PM
Peter,
Welcome back! 
And, I'm impressed sir! 

73,
John,  KA4WJA


Title: RE: Ham Xcvrs' and Amps', Transmit Spectral Purity, IMD Products, vs. comm/maritime
Post by: KA4WJA on February 23, 2018, 03:32:42 PM
Brian,
No worries here...we all have our opinions and points of view...


Ironically, since I do not wish for gov't regulations, it's strange that I find myself reminding everyone of the rules that do not exist... Pretty weird, huh?  :)

I just wanted everyone to understand that there are no IMD specs / requirements that govern amateur radio service emissions...none...
except of course to the extent that these IMD products extend "out-of-band", outside of your license privilege areas, and/or cause interference to other radio users (whether other amateur radio stations or those in other services)...

Of course, Part 97.307 (b) does state:  "Emissions outside the necessary bandwidth must not cause splatter or keyclick interference to operations on adjacent frequencies."
So, IMD products (which are emissions from your transmitter) must not cause splatter or interference...

But, that's the only "rule" that can be inferred to be speaking of IMD products...

Just wanted everyone to remember that.  :)



As hams, we are responsible for our signals, NOT the radio manufacturers...
A major problem now-a-days is that many hams (not you, Brian) assume that if the radio is sold in the US it must be approved for our use...and while that is true, and if it's got a processor in it, it needs to meet Part 15 regs, but that's about it, as far as being "approved"....'cuz it is up to the operator to "approve" their own signal and keep from interfering with others...
(and again, here we find that many hams do not understand what IMD products are, nor how they are caused, nor especially how to improve them and not cause interference.. :(


We all need to be remember that it's up to us to do this...not a gov't!

And, hence the impetus for this thread....as many of our modern rigs, even when operated completely within their design specs / settings, will splatter and interfere with other stations on adjacent freqs...
And, that's why I started this whole discussion... :)


Anyway, gotta' go.

73,  
John,  KA4WJA
 


Title: RE: Ham Xcvrs' and Amps', Transmit Spectral Purity, IMD Products, vs. comm/maritime
Post by: SM0AOM on February 23, 2018, 11:52:22 PM

All Knobs To The Right along with trying to get the needle to 100W on a non-peak reading power meter are all a matter of training. If ham radio operators cannot or will not get this training then the manufacturers need to add more functionality to transceivers such as removing the microphone gain control and making all power meters peak reading. Yep, we need idiot proof transceivers, and that's sad.


I believe that this is the major underlying cause. Lowering of the exam standards has permitted idiots into amateur radio,and thus we have to face the consequences and need "idiot-proof" Equipment. This is a sad state of affairs, but is an effect of the "quantity Before quality" thinking. When the competence is comparable to CB, the privileges should correspond.


Unlike other opinions here, I strongly believe in regulation in these matters, privileges should be quite closely matched to competence. "Instant hams" should not be allowed to use other than channelised type-approved low-power transmitters.

Access to adequate spectrum analysis and power measurement gear and some form of proper radio engineering education should be required to operate higher-powered gear above, say 50 W. This would also be benefical in other aspects, the EMF exposure and RF interference issues would be much easier handled.

This said on the requlatory aspects. Here in Europe, we know that regulations work, for example Germans do as they are being told, and I believe that this also is the case for amateur radio.

What criteria should be applied when choosing spectrum mask requirements is somewhat "knotty".

From experience, the ARINC 719 spectrum masks used for aeronautical HF spectrum planning are "good enough" for the lower powered equipment.They result in first and second speech modulated adjacent channels of about -50 and -60 dB respectively. Higher powered equipment would need to be about 10 dB better.


It remains to be seen how these emission standards is implemented in modern radio gear.
A quite substantial improvement could result by just removing the mic-gain control and redesigning the ALC Circuits to just handle peak clipping, so the ALC modulation issues are avoided. Audio level setting should be handled by VOGAD, RF by TGC and speech processing by suitable means in the transmit IF chain.

Otherwise, proper engineering practices need to be applied in transmitter design, such as derating, gain distribution and RF negative feedback. Proper power supply design would also help.

If we enter the SDR domain, a "magic bullet" is adaptive predistorsion. By proper application, it would be possible to reduce the adjacent channel products with at least 25 dB, which is more than can be acheived by any other means.

It also permits the implementation of high-efficiency linear amplifier designs which may reduce heat stress on circuits and cooling requirements.
If designed in from the beginning in future SDR gear, adaptive predistorsion would not contribute much to the total cost, and may be somewhat offset by lower cooling demands.


Title: RE: Ham Xcvrs' and Amps', Transmit Spectral Purity, IMD Products, vs. comm/maritime
Post by: G3RZP on February 24, 2018, 05:19:56 AM
There is no doubt that the last generation of hybrid rigs with a tube PA (especially those with 6146Bs rather than sweep tubes) were much cleaner on high order IMD than practically any of the SS rigs that followed them, with few exceptions.

These days however, we are rapidly getting to the stage where only those amateurs living in an electrically quiet rural area will be able to garner any advantage of people having cleaner transmitters.


Title: RE: Ham Xcvrs' and Amps', Transmit Spectral Purity, IMD Products, vs. comm/maritime
Post by: W6RZ on February 24, 2018, 05:20:49 AM
When I lived on the East Coast during the peak of Cycle 21 (late 70's), I used to get up at the crack of dawn on weekends to listen for Eastern Europeans on 10 meters. Many of these guys in the Ukraine and other Soviet Union countries had weak and horribly distorted SSB signals. You could tell that they had home brewed their transmitters with whatever components they could find.

I was way more impressed with their passion to get on the air than dismayed by the quality of their signals.


Title: RE: Ham Xcvrs' and Amps', Transmit Spectral Purity, IMD Products, vs. comm/maritime
Post by: SM0AOM on February 24, 2018, 08:18:17 AM
These days however, we are rapidly getting to the stage where only those amateurs living in an electrically quiet rural area will be able to garner any advantage of people having cleaner transmitters.

They would not have any significant advantage of good receivers either, if the live in a bad RFI environment.
Really good receivers would only be significant when you had really close neighbours using really good transmitters.

If we make the thought experiment that amateur radio would become channelised and frequency planned I am of the opinion that receivers with 70 dB Close-in dynamic range would be perfectly adequate.

People tend to give out inflated signal repots, but I very much doubt that the real RF C/I exceeds 70 dB over a significant fraction of an operating year.

Perhaps applyng the old "rule-of-thumb" of 90 dB between isotropic antennas may give some higher figures, +57-5-90-5 =-43 dBm received signal, or S9+30.

The noise floor on 80 meters may be estimated as -174+30+35 = -109 dBm. In this case, the RF C/N would have been 66 dB in an SSB bandwidth.


Title: RE: Ham Xcvrs' and Amps', Transmit Spectral Purity, IMD Products, vs. comm/maritime
Post by: AC2RY on February 24, 2018, 08:59:51 AM

If we make the thought experiment that amateur radio would become channelised and frequency planned I am of the opinion that receivers with 70 dB Close-in dynamic range would be perfectly adequate.

People tend to give out inflated signal repots, but I very much doubt that the real RF C/I exceeds 70 dB over a significant fraction of an operating year.

Perhaps applyng the old "rule-of-thumb" of 90 dB between isotropic antennas may give some higher figures, +57-5-90-5 =-43 dBm received signal, or S9+30.

The noise floor on 80 meters may be estimated as -174+30+35 = -109 dBm. In this case, the RF C/N would have been 66 dB in an SSB bandwidth.

I disagree that we need more restrictions on HAMs working in the air. That is bad practice and won't have much understanding in US and other places. Though what is really needed - stronger certification checks for hardware sold on the market (It would definitely makes sense to ADD adjacent channel emission limit) and also enforcement of signal quality in the air. If enough people complain about someone's poor signal quality - his/her station should be evaluated by officials and license suspended if violation of emission rules is confirmed. Just like with conducting HAM license exams, evaluations can be done by volunteers certified to do that work.




Title: RE: Ham Xcvrs' and Amps', Transmit Spectral Purity, IMD Products, vs. comm/maritime
Post by: KM3F on February 24, 2018, 03:22:23 PM
This threads is really getting far fetched now!


Title: RE: Ham Xcvrs' and Amps', Transmit Spectral Purity, IMD Products, vs. comm/maritime
Post by: KM1H on February 24, 2018, 04:17:16 PM
Ive been too busy to shovel thru long winded posts so I hope you dont mind if I tackle single subjects for now.

Quote
As for the "tones"....use of non-harmonically-related audio tones (between 300hz and 3000hz), spaced at least 1000hz apart, for IMD testing of communications equipment was established by Bell Labs many years before I was born...(and I think even decades before Carl was born..Smiley
I don't think the ARRL is doing anything other than what has been accepted engineering practice for many years (decades!!)

The original Bell specs are ancient.

The current requirements for  analog lines measure out to the 5th order and start with fundamentals in the 315-1000 Hz range.This is a full range and not just two tones cherry picked for the best results to satisfy ham manufacturers and make their consumers "feel good".
The ARRL and their advertisers have used the "relaxed" cherry picked version for many decades and has not  been "accepted engineering practice" outside consumer grade products which includes CB. Certainly not marine, military, and telcom products

Read an Eimac manual for the methods they use to specify IMD

The ARRL uses 14.0212 and 14.0200 as test frequencies for amplifiers and 700-1900 Hz for transmitters which is a difference of 1200 Hz and puts the IMD3 well down the slope of the SSB filter pass band. Those are cherry picked to give far better results than reality.

White noise is the only accurate test and the ARRL already owns an Elecraft noise generator.

Carl


Title: RE: Ham Xcvrs' and Amps', Transmit Spectral Purity, IMD Products, vs. comm/maritime
Post by: KB2TIS on February 24, 2018, 04:42:43 PM
emissions mask??  Here's the older one...(will look for the newer one)....

Page 62 of ITU-R SM.1541-3?

https://www.itu.int/dms_pubrec/itu-r/rec/sm/R-REC-SM.1541-3-201101-S!!PDF-E.pdf

50-150% 25 dBc
150-250% 35 dBc

% is % of necessary bandwidth 


Title: RE: Ham Xcvrs' and Amps', Transmit Spectral Purity, IMD Products, vs. comm/maritime
Post by: AA2UK on February 24, 2018, 04:57:59 PM
Talking about cherry picking figures, when CushCraft forever changed antenna gain figures from dbd to dbi for ARRL advertising, ask Dave K1WHS
Bill, AA2UK


Title: RE: Ham Xcvrs' and Amps', Transmit Spectral Purity, IMD Products, vs. comm/maritime
Post by: KM1H on February 24, 2018, 05:48:53 PM
CC wasnt the only one. Most all did it to some degree including adding ground gain to dBd. A few of the lesser players may have done it to dBi ;D ::)

Carl


Title: RE: Ham Xcvrs' and Amps', Transmit Spectral Purity, IMD Products, vs. comm/maritime
Post by: AA2UK on February 24, 2018, 06:03:38 PM
Ground gain came after dbi over dbd. At least that's my memory Carl.
Dave tells a pretty humorous story, but he quit CC over the fight between marketing and engineering when the change was made. The late Tom Kirby W1EJ back this up.
Bill, AA2UK


Title: RE: Ham Xcvrs' and Amps', Transmit Spectral Purity, IMD Products, vs. comm/maritime
Post by: KM1H on February 24, 2018, 06:18:15 PM
Tom lived about 5 miles from me in the same town. When I moved to the hilltop he got pissed when I started beating him in 6M DX pileups. Then came the 16 el bedspring and the CC 617B mod to 8 el which added almost 2 dB. That was a pre computer 70's design with fairly sloppy performance but still better than most others.

I think he used QLF on CW ::)

Carl


Title: RE: Ham Xcvrs' and Amps', Transmit Spectral Purity, IMD Products, vs. comm/maritime
Post by: W6RZ on February 25, 2018, 04:46:03 AM
White noise is the only accurate test and the ARRL already owns an Elecraft noise generator.

White noise IMD measurements are cool, but the PEP of noise like signals is probabilistic. How do you set the drive level of a white noise IMD measurement?

Is it set so that no waveform peak exceeds the PEP rating of the amplifier? That would be very forgiving. For the typical 100 watt PA, the average power would only be around 10 watts.

Or is the drive level set so that some percentage of the waveform peaks exceed the PEP rating of the amplifier? What percentage makes sense? 10 percent, 20 percent, or what?

Seems like a big bag of worms to me (compared to the precisely defined levels of a two-tone test).


Title: RE: Ham Xcvrs' and Amps', Transmit Spectral Purity, IMD Products, vs. comm/maritime
Post by: KM1H on February 25, 2018, 07:47:50 AM
Start with setting the power to the advertised spec. Then using a good peak reading wattmeter adjust the noise generator so the peaks do not exceed that level.

Many if not all transceivers have their best IMD at some point below the max, 75-85W is a sweet spot for many 100W rigs. It would be nice to make comparative tests as I have done with mine and several others over the years and achieve in the low to mid -40's using the proper professional method.....not the ARRL's

Another good test that I have used on AM and SSB is to use the human voice in a repetitive loop with extremely low distortion; there are several ways to accomplish that.

Carl


Title: RE: Ham Xcvrs' and Amps', Transmit Spectral Purity, IMD Products, vs. comm/maritime
Post by: SM0AOM on February 25, 2018, 12:18:09 PM
Establishing the proper drive level for noise-loading IMD tests is indeed "a can of worms".

However, there is some guidance in looking at the statistics of band-limited gaussian noise,and compare it to known statistics of other waveforms.

Speech has a long-time average to peak ratio of about 8 dB, which corresponds to slightly less than 1% of the noise peaks exceeding
a given PEP.
For noise loading IMD tests, it would then be a reasonable approximation to adjust the noise input so the average power is around
1/8 of the nominal PEP.

For more details; http://www.empowerrf.com/rf-amplifiers/index.php?topic=MeasuringP1dB

There is a procedure indicated in MIL-STD 188-141B section 22 where the minimum suppression of intermodulation noise
in an ISB transmitter is specified to be at least 35 dB when one adjacent noise-loaded channel is replaced with an 1 kHz tone while keeping the total PEP constant.

In my opinion, most modern ISB transmitters do considerably better than that,
my own SRT SSA1000 has been measured to provide better than -50 dB with noise and recorded voice excitation.

Better than 70 dB should be attainable using adaptive predistorsion.


Title: RE: Ham Xcvrs' and Amps', Transmit Spectral Purity, IMD Products, vs. comm/maritime
Post by: K6AER on February 25, 2018, 08:44:27 PM
Given the utopia of a -60 dB IMD radio to improve the bands I was wondering who will be in charge for rounding up all the old transceivers and how are you  going to get the other 189 countries to do the same?


Title: RE: Ham Xcvrs' and Amps', Transmit Spectral Purity, IMD Products, vs. comm/maritime
Post by: SM0AOM on February 26, 2018, 01:33:17 AM
Maybe the "all knobs to the right" and general ignorance cultures in amateur radio have already gone too far.

There is a general decline in behaviour and engineering standards,
a clean emission is no longer the matter of honour that is was one or two generations ago.

A lot of newly introduced equipment has simply anti-social adjacent channel characteristics, and some newer rigs and LDMOS amplifiers bear witness to this:

Even 'Linear amplifiers' are not necessarily so. G3SJX reviewed the Expert 1.3K-FA amplifier in July RadCom.
He found the 3rd order IMD at outputs of 1.3 to 1.5kW to be  -20 to -26dB relative to PEP - that's -13 to -20dB relative to one tone of a 2 tone signal. At 1kW, it was -30dB  rel PEP  i.e. -24dB relative to tone.

Not exactly brilliant

As the transfer functions of run-of-the mill LDMOS amplifiers also favour the generation of high-order IMD products when driven close to saturation, the situation is even worse than G3SJX measurements indicate.


Title: RE: Ham Xcvrs' and Amps', Transmit Spectral Purity, IMD Products, vs. comm/maritime
Post by: G3RZP on February 26, 2018, 02:20:13 AM
The Hilberling amplifier reviewed in RadCom did not meet European standards (and not even the more relaxed US ones) for harmonics on several bands, either. Admittedly, the tests were not done in a certified lab, so must be treated with some degree of suspicion.


Title: RE: Ham Xcvrs' and Amps', Transmit Spectral Purity, IMD Products, vs. comm/maritime
Post by: KA4WJA on March 08, 2018, 06:03:54 PM
Wow, I've been away from here for a couple weeks, and you guys have done a fantastic job of discussing these matters!!  And, I am happy that this topic has spurred such a learned discussion!!  Please continue!!  I will try to stop back when I can... :)

Though, like Carl, I don't have the time / inclination to comment further on all of these points...'cuz if I tried to breeze thru all of them, I'd feel like I'd be where LBJ once described: "Caught out on a dark highway in a Texas hail storm, can't run, can't hide, can't make it stop!"  So, this will probably be my last post here for a while... :)

BUT...

But, the good news is that I actually agree with some of what Carl wrote!!

Yep, that's not a typo, I agree with Carl!!  (Not all, of course, but at least some of it) :)  

I agree with both:

a)  the ARRL editorial polices suck!  They won't call a spade, a spade....and refuse to do any more than an occasional few words about poor IMD!!

I can't look for 'em all, but when discussing IMD, this post came to mind....From the thread: "Better IMD please":

The latest QST has a review of a TE 2M brick and they give it a -17dB 3rd and barely comment its not as good as they would like to see. The other ones arent much better.
Jeez, how can they even accept advertising for that crap?? No conscience required when money crosses hands in ad revenue.

Carl

For clarification here, this is referring to a TE Systems 1410G amp, and the ARRL tests results were -17 / -29 / -37 / -44

And, the only ARRL comment about these horrible specs was:  "At full output, transmit intermodulation distortion (IMD) products are higher than we’d like to see and could interfere with nearby stations."  (and that's one of the most critical IMD comment I've ever seen from the ARRL, in my 45 years of membership!)

So, we agree that the ARRL won't stand up for squat, save for their advertisers or political pundants...and it seems that we also agree that we should actually use their lab test results to better understand some of what these manufacturers are trying to pawn-off on us!!  :)   And, since the ARRL has been using these same test procedures for decades....well, you can all see that the "cherry picked" argument is just argument, and not really anything to discuss further... :)

Oh, and I have read the Eimac manual, which primarily deals with PA's specifically, and only minor comment on transceivers.....but they use examples of 2000hz separation of signals into the amplifiers / tube test jigs (just as the ARRL does)....and show example using 2100hz separation of signals / audio tones, presumably as example of testing SSB transceivers/transmitters...which of course does space out the IMD products, BUT...
But, of course 99% (all???) of the IMD products we are discussing / dealing with here, are coming from the transceiver's PA, so the comment about the ARRL's 1200hz separation of tones for testing SSB transceivers, "puts the IMD3 well down the slope of the SSB filter pass band.", is a red herring and has no bearing on this discussion at all...and I'm quite surprised that the same folks that correctly comment about our transmitters' splatter (transmit IMD) not being "filterable", seem to think that the 2-tone-test results are "filterable"??  Huh??  Fact is, this is such a red herring, I can only assume that the author simply got confused when typing... :)

So, I'm wondering how if the ARRL test results were useful in 2011, and Eimac (and ARRL) actually uses wider tone spacing for testing tubes (amplifiers), and telcos testing for analog baseband linearity of course use lower/narrower spacing (to allow IMD products inside the baseband passband be seen/tested...etc), etc. etc...I'm wondering how these can be considered "cherry picked", as they are testing different things / different applications??

http://www.cpii.com/docs/related/22/C&F4Web.pdf

Yes Eimac uses dbc vs. db(PEP): (which we all have already known), "The standard method of specifying the magnitude of the distortion products is to specify the reduction in decibels of
one product from one tone of a two-equal-tone signal."
 And they specifically warn against comparing the numbers as there is of course a 6db difference...and as I wrote many times, any ham that cannot grasp the difference between dbc and db(PEP), and cannot add/subtract 6, probably isn't going to understand what IMD is...

Eimac, also warns against drawing conclusions about amplifier IMD based solely of tests at max drive power, as "maximum intermodulation distortion does not necessarily occur at maximum drive.....plots of IMD level (Y axis) referred to the driving signal expressed as a ratio of drive to operating bias. As the drive is increased, the various IMD products pass through maxima and minima. Misleading conclusions of amplifier performance may be drawn if the equipment happens to be tested near cusp on the IMD curve, where a particular product drops to an extremely low level. The whole operating range of the equipment must be examined to draw a true picture of IMD performance." But, this is about variations in curves based on drive power and operating bias, not about the freq or spacing of the "tones"!  Meaning that at various drive levels, different bias levels can be used to show different IMD levels, just as I mentioned weeks ago, where I wrote about PA design / biasing (and tuning) can be done to reduce some IMD products at the expense of increases in other IMD products, and how that can change with various drive levels...(whether we're talking about tube PA's and using Eimac words...or referring to SS PA's and using Motorola words, etc. etc. etc...the physics doesn't change...:) )

Here are some further quotes from Eimac:  "...this simple test [single-tone test] lacks information on the linearity of the stage. To study linearity thoroughly by observing the amplifier output, some means must be provided to vary the output level from zero to maximum signal with a regular pattern that is easily interpreted. A simple means is to use two audio tones of equal amplitude to modulate the single-sideband transmitter. This is termed a two-tone test. This procedure causes the transmitter to emit two steady signals separated by the frequency difference of the two audio tones.

Figure 45. Spectrum of SSB transmitter modulated by two-tone test signal containing 400- and 2500-Hz tones and transmitting upper sideband.

When measuring the distortion of a linear RF amplifier or a chain of linear RF amplifiers by the two-tone technique, it is sometimes more expedient to use two RF signal sources separated in frequency by the desired number of hertz, and then to combine them in a manner which will minimize the interaction of the two signals."
[what the ARRL does]

"The Intermodulation Distortion Test Console at EIMAC uses two separate RF signal sources 2000 Hz apart. The two test signals are at 2.001 and 2.003 MHz. The signals are combined in a
toroidal hybrid combiner and amplified by a 4CX5000A operating as a Class A amplifier. The 4CX5000A stage is loaded with a 50- ohm non-inductive load in addition to the impedance of the input circuit of the tube under test. The test amplifier can evaluate many different tube types and is capable of all classes of operation. It may be grid-driven or cathode-driven."
[the same 2000hz spacing as the ARRL, when testing amps]


b)  The other thing we agree on, is the "age" of the old telco specs are...well, they're old!!  :)

Yes, those old telco specs are old / ancient....and, of course, that's because telcos haven't used SSB-FDM in a LONG time (almost gone by the early 80's...and it was being phased-out down here in the SE US, in the mid-80's and except for some international satellite telco links it was all but gone by early 90's).  Then, since there was added concern about linearity in the analog baseband, and concerns about this causing problems in the early A/D codecs, telcos began testing beasband linearity, so they used much lower tones...

Of course this does not diminish the fact that if you do wish to test an SSB transceiver, and see how it might interfere with communications on adjacent frequencies, the accepted way (by Motorola, Vertex, Harris, etc., the FCC, etc., and even Eimac) is by using non-harmonically-related audio tones, spaced by 1000hz or greater...

(yes, "dynamic testing" where a third "dither" tone is used, is certainly superior, as this shows both the effects of power-supply issues and some of the complexities of speech in a scientifically repeatable way....but since static two-tone test data is what we have available to use in comparing various radios, I stand behind my earlier comment/question, why not use what data we have to better understand and evaluate our transceivers??)

As for using white noise, assuming you're setting the white noise level for max rated PEP, there is little difference in the results of the tests, but it's easier to show laypersons how these IMD products effect adjacent frequencies...

(http://i67.tinypic.com/2hdsnde.jpg)



So, you see Carl and I are actually in some agreement here!  :)   Miracles do happen :)

Again, I thank everyone here for contributing to this discussion!  I hope it continues...and I will try to stop back and check-in from time-to-time, but I've had my say and made my points clear...so, thanks to you all!  :)

And, sorry for the ramble....but this oft repeated myth about ARRL using "cherry picked" tones, just peeves me.....Yep, the ARRL BS about IMD and their lack of back-bone is pretty disgusting, but their test procedures are not flawed anymore than those of Eimac, etc..  :)


73,

John, KA4WJA




Title: RE: Ham Xcvrs' and Amps', Transmit Spectral Purity, IMD Products, vs. comm/maritime
Post by: W6RZ on March 09, 2018, 03:13:33 AM
Measuring the power of a noise like signal with a spectrum analyzer requires compensation. What is the power level of this signal?

(http://www.w6rz.net/ofdmpower1.png)


Title: RE: Ham Xcvrs' and Amps', Transmit Spectral Purity, IMD Products, vs. comm/maritime
Post by: AC2RY on March 09, 2018, 05:47:37 AM
Measuring the power of a noise like signal with a spectrum analyzer requires compensation. What is the power level of this signal?

(http://www.w6rz.net/ofdmpower1.png)

Modern analyzers readily calculate PEP, RMS and any other view at power. In testing simple numbers are not the point. What we need to see is two pictures: spectrum at input and output of device under test. And linear amplifier should be tested with RF signal synthesized for that purpose. Today you do not need fancy combiners at least at HF frequencies, as signal can be created digitally and then converted to analog by 14-16 bit DAC working at sampling rate 10x higher than test signal frequency. In that case we even do not need to see input spectrum - any remaining distortion products will be below -80dB level.

As to IMD in audio signal - these measurements are useless when everyone uses speech compressors. The only thing we need to know is how much attenuation is happening outside of passband. Noise type test signal is the best for that. Again we should see spectrum, and not get a single number.




Title: RE: Ham Xcvrs' and Amps', Transmit Spectral Purity, IMD Products, vs. comm/maritime
Post by: W6RZ on March 09, 2018, 06:13:13 AM
Modern analyzers readily calculate PEP, RMS and any other view at power. In testing simple numbers are not the point. What we need to see is two pictures: spectrum at input and output of device under test. And linear amplifier should be tested with RF signal synthesized for that purpose. Today you do not need fancy combiners at least at HF frequencies, as signal can be created digitally and then converted to analog by 14-16 bit DAC working at sampling rate 10x higher than test signal frequency. In that case we even do not need to see input spectrum - any remaining distortion products will be below -80dB level.

As to IMD in audio signal - these measurements are useless when everyone uses speech compressors. The only thing we need to know is how much attenuation is happening outside of passband. Noise type test signal is the best for that. Again we should see spectrum, and not get a single number.

I agree with all of that. I used an SDR to create that waveform. I was just wondering what the power levels were in the pic posted by KA4WJA. I don't see how the PEP levels could be matched.

(http://i67.tinypic.com/2hdsnde.jpg)


Title: RE: Ham Xcvrs' and Amps', Transmit Spectral Purity, IMD Products, vs. comm/maritime
Post by: KA4WJA on March 09, 2018, 07:50:07 AM
Ron,
That is a scan of a two-tone test and superimposed white noise test, of an IC-781, done by Rob Sherwood, NC0B...(I believe it is his personal IC-781, as that is his favorite rig to use)

(http://i66.tinypic.com/15gz0cj.png)

I was just wondering what the power levels were in the pic posted by KA4WJA. I don't see how the PEP levels could be matched.
(http://i67.tinypic.com/2hdsnde.jpg)

And, I believe it is operating at its rated output, 150 watts....

I was just using this scan as an example to show how a "2-tone IMD test" compares to a "white noise IMD test"....you can use a white noise IMD scan to more easily show novices what the result of poor IMD is....and, while the myth seems to persist that somehow white tests are better, fact is they show the same "static" results....
This is why "dynamic testing" (using a dithered third tone) is considered a better test....but I don't have the generating equip to do these, nor do most hams....and, of course "2-tone test data" is what we have a plethora of, so that's what we use to compare things.. :)


But, more on-point, setting of white noise level for IMD testing, is usually done by use of a reasonably repeatable peak-reading watt meter, and setting the white noise level until the transceiver's rated PEP output is shown.
(at least that's how I've done it....of course, in a lab, you'd have many ways to measure the transceiver's PEP output, but use of an accurate power meter, with the transceiver terminated into a known good dummy load, is the way I was taught...and back then we didn't have LP-100's or "pwer-masters, etc., just Bird's and HP's.)
Just as you would do with a single-tone test, two-tone test, etc...


Hope that helps??

73,
John,  KA4WJA


P.S.  As for the scan that you posted, since it's from a Rigol analyzer, remember that you can measure the Channel Power right from the instrument....and get results of both the Channel Power and Spectral Power Density (down to the 1/100 of a dbm, if you desire), right on the display....
(but, just looking at it, it looks darn close to -60dbm signal...plus whatever attenuation you have upstream....but if you measured the Channel Power, you'd of course need to specify the Channel Integration Bandwidth, etc., to get the exact Channel Power...is this a 6mhz channel??, etc.??)



Title: RE: Ham Xcvrs' and Amps', Transmit Spectral Purity, IMD Products, vs. comm/maritime
Post by: W6RZ on March 09, 2018, 08:39:46 AM
Thanx for the response. The actual average power of the scan I posted is -38.23 dBm. I was just trying to show that the analyzer RBW (resolution bandwidth) makes a big difference when measuring noise like signals. You can estimate the real power level by just taking the log of the ratio of signal bandwidth to RBW. In this case:

RBW = 30000 Hz
Signal bandwidth = 5700000 Hz

10 * log10 30000/5700000 = -22.8 dB

So -60 dBm + 22.8 dB = -37.2 dBm (pretty good estimate)

But in the NC0B scan the power level of the noise signal would be 10 dB higher (3 kHz / 300Hz RBW) than the tones, and the PEP would be even higher. Although he may have actually matched the PEP levels, I'm getting the feeling he "doctored" the image to make the IMD profile match.

I'm just curious if I can replicate these results with my SDR setup where I can set power levels fairly accurately and not rely on a PEP watt meter with unknown characteristics. Stay tuned for more measurements.

Here's the channel power measurement.

(http://www.w6rz.net/ofdmpower2.png)



Title: RE: Ham Xcvrs' and Amps', Transmit Spectral Purity, IMD Products, vs. comm/maritime
Post by: W6RZ on March 12, 2018, 03:41:43 PM
Here's the first set of measurements.

1) Two-tone test where the 3rd order IMD is 30 dB down from a single tone.

2) Channel power of two-tone signal.

3) Noise signal with PEP set exactly to PEP of two-tone test.

4) Channel power of noise signal.

5) Noise signal with maximum peak function on spectrum analyzer.

6) Composite of 4 and 5.

7) CCDF of the noise signal.

As I expected, setting the PEP level of the noise signal to the PEP level of the two-tone signal is way too lenient. The IMD of the noise signal is about 43 dB below the average power while the IMD of the two-tone signal is 33 dB down from the average power. A 10 dB discrepancy.

The calculated peak to average power ratio of the noise signal is 9.16 dB.

The channel power of the two-tone signal is -16.47 dBm. The channel power of the noise signal is -23.26 dBm for a measured difference of -6.79 dB. The calculated difference was 10 log 0.112004/0.461087 = -6.15 dB. Here's the statistics of the IQ stream for each signal. Note that the peak power levels are matched.

Code:
two-tone signal
Peak magnitude = 0.960302
average power = 0.461087, peak power = 0.922180 @ 0

Maximum PAPR = 3.010327
percentage above 0 dB = 50.01776814
percentage above 1 dB = 41.68390632
percentage above 2 dB = 30.09487092
percentage above 3 dB = 3.10766175

peak real positive = 0.960302, peak imaginary positive = 0.960302
peak real negative = -0.960302, peak imaginary negative = -0.960302

peak real positive @ 0, peak imaginary positive @ 601
peak real negative @ 400, peak imaginary negative @ 201

noise signal
Peak magnitude = 0.960300
average power = 0.112004, peak power = 0.922176 @ 487056344

Maximum PAPR = 9.155787
percentage above 0 dB = 36.81914806
percentage above 1 dB = 28.42292786
percentage above 2 dB = 20.51521093
percentage above 3 dB = 13.60431314
percentage above 4 dB = 8.11254755
percentage above 5 dB = 4.22813781
percentage above 6 dB = 1.85978524
percentage above 7 dB = 0.66086547
percentage above 8 dB = 0.17963439
percentage above 9 dB = 0.03466571

peak real positive = 0.960277, peak imaginary positive = 0.960295
peak real negative = -0.960295, peak imaginary negative = -0.960292

peak real positive @ 6754218120, peak imaginary positive @ 21616586385
peak real negative @ 3357484312, peak imaginary negative @ 2768866993

(http://www.w6rz.net/twotone.png)

(http://www.w6rz.net/twopower.png)

(http://www.w6rz.net/noise.png)

(http://www.w6rz.net/noisepow.png)

(http://www.w6rz.net/peak.png)

(http://www.w6rz.net/noisepeak.png)

(http://www.w6rz.net/t2paprweb.png)


Title: RE: Ham Xcvrs' and Amps', Transmit Spectral Purity, IMD Products, vs. comm/maritime
Post by: W6RZ on March 12, 2018, 03:44:32 PM
BTW, the schmutz on the sides of the signal in maximum peak mode is not IMD. It's just the way that an OFDM signal works. There's occasional out of band transients.


Title: RE: Ham Xcvrs' and Amps', Transmit Spectral Purity, IMD Products, vs. comm/maritime
Post by: VK3BL on March 13, 2018, 07:02:17 PM
If anyone wants to see what IMD testing looks like visually rather than just static pictures, check out my following videos:

Real World Performance (recorded voice loop):
https://youtu.be/Wgkv1Gyq4wg

Two tone & white noise:
https://youtu.be/Sc_6ST5NK3k

In the videos I vary the power levels, and it is especially interesting in the two tone video to see how the 3rd and 5th order products vary as power levels change.  I run from 100w to 1w and back again in the video.

Might not interest everyone, but for me personally it was very enlightening to see how the PA stage really worked as such.

PS, details of my test equipment and sample files etc are in the description of the videos :)


Title: RE: Ham Xcvrs' and Amps', Transmit Spectral Purity, IMD Products, vs. comm/maritime
Post by: KA4WJA on March 15, 2018, 06:01:42 PM
Ron,
I've not spoken to Rob about this particular scan/test...but assume he did as I would do (and everyone else I know) and adjust the white noise level (just as you would the tone levels) to drive the rig to its max rated PEP output...
Whether he used a modern peak-reading watt meter, or measured the voltage across the 50-ohm dummy load (~ 245Vp-p = ~ 150 watts), or used an RF power meter thru attenuators, etc???  [I've done all three of these myself...as well as using power atten and/or directional couplers, and spec analyzer, but but find the meters to better]
I'm not sure what his exact measuring / adjusting procedure was, but assume it was one of the accepted standards.  :)

But, I'm fairly certain there was no "doctoring" involved... :)
But in the NC0B scan the power level of the noise signal would be 10 dB higher (3 kHz / 300Hz RBW) than the tones, and the PEP would be even higher. Although he may have actually matched the PEP levels, I'm getting the feeling he "doctored" the image to make the IMD profile match.

I'm just curious if I can replicate these results with my SDR setup where I can set power levels fairly accurately and not rely on a PEP watt meter with unknown characteristics. Stay tuned for more measurements.

As for SDR's being used as test equipment??
I haven't any experience with that....and I suggest you start a new thread on this particular subject.  (or perhaps there already is one, in the SDR section??)

In any case, I'd be interested if they are accurate enough to be useful?
So, please go for it.

73,
John,  KA4WJA


Title: RE: Ham Xcvrs' and Amps', Transmit Spectral Purity, IMD Products, vs. comm/maritime
Post by: KA4WJA on March 15, 2018, 06:20:12 PM
Ron, Jarrad, et al,

I'm glad this discussion has spurred some enthusiasm, and I'm sure if you start your own thread about modern spec analyzers' test abilities and various tests you've done, and how SDR's can be used as test gear, etc., there would be much more interest and many who would wish to join in.

But, since here we are discussing our modern HF transceivers' IMD specs, and how there has been a change for the worse over the past 40 - 50 years....as well as comparisons of various PA's and how in theory a higher-voltage PA would allow for better IMD (more time in the linear range, and less time in the transition), but how this "12vdc vs. higher-voltage PA" comparison isn't as easy as it seems, as the actual devices used, the actual design, and the biasing / tuning of any particular PA has significant effect, etc....I think your tests, and images might be getting lost in the woods (there are few reading this far into this thread, who aren't already well involved in RF), so perhaps you guys could start a new thread??  :)

Again, thanks for contributing here, and why not start a new thread? 
I know I'd be interested....especially in the peak power measurements of OFDM signals (where the actual peak value is highly dependent on measurement time), 'cuz I don't have personal experience with that.


Fair winds.

73,

John,  KA4WJA


P.S.  Ron (W6RZ), idea for your new thread....testing of OFDM signals...
I've no experience measuring PEP for a 6mhz - 7.5mhz wide OFDM signal...
{in this above discussion, of HF SSB signals, I know the way I learned years ago (now well out-dated) was to use a scope to measure the voltage across a 50-ohn load, and more recently use an accurate peak-reading watt meter...does this wok for OFDM signals??  Or do you need a modern analyzer to do channel power measurements??}

I read these papers the other day. but haven't experience with power testing of OFDM signals...

http://www.nts-cs.com/elliott/collateral/white_papers/OFDM.pdf
Here is a quote from this paper:
Quote
The dynamic nature of signals that use Orthogonal Frequency
Division Multiplexing (OFDM) is such that these various
methods can give widely different results depending on the type
of measuring instrument used and the power measurement
required. The requirements for output power in the regulatory
standards can be confusing, leading to incorrect or inaccurate
measurements.

And, another paper on OFDM power.
https://karriere.rohde-schwarz.de/career-cdn-pull/rs-common/fileadmin/customer/downloads/PDF/Huellkurve_eng.pdf



P.S.  Jarrad (VK3BL), I like your videos....and I think there may be a slight confusion (based on "being separated by a common language", hi, hi).  You say that using white noise better shows the actual IMD....and while it does allow many to better see the effects of the IMD, it should actually show the same thing, just that we can more logically see its effect. :)

In my personal experience, if using white noise, a good peak-reading power meter, or a accurate scope for the freq of operation, will be necessary to adjust the noise input level...just like if doing a 2-tone test, to adjust the tone levels...
Except for any changes in the analyzer settings, etc., the results at any freq outside of the baseband passband should be the same, just that you'd have to imagine tones filling in the spaces... :)



Title: RE: Ham Xcvrs' and Amps', Transmit Spectral Purity, IMD Products, vs. comm/maritime
Post by: W6RZ on March 15, 2018, 07:12:37 PM
Quote
The dynamic nature of signals that use Orthogonal Frequency Division Multiplexing (OFDM) is such that these various methods can give widely different results depending on the type of measuring instrument used and the power measurement required. The requirements for output power in the regulatory standards can be confusing, leading to incorrect or inaccurate measurements.

I'm glad you posted that, because the very same thing can be said about a white noise signal.

All I'm saying is that white noise testing seems entirely useless until there's a specific testing protocol to follow (just like the two-tone test). However, there are so many variables (for example, as you mentioned, measurement time), I'm not sure that a testing protocol that can provide repeatable and comparable results from different testers is even attainable.



Title: RE: Ham Xcvrs' and Amps', Transmit Spectral Purity, IMD Products, vs. comm/maritime
Post by: KM1H on March 16, 2018, 07:02:55 AM
Several AMers have written about their tests using a human voice and music to measure the distortion output from their Class C or linear RF stages.

Why cant that be used on SSB? It would be easier to do and a standard voice or music recording would eliminate a lot of discussions over white noise standards.

Carl


Title: RE: Ham Xcvrs' and Amps', Transmit Spectral Purity, IMD Products, vs. comm/maritime
Post by: AC2RY on March 16, 2018, 03:41:50 PM
Several AMers have written about their tests using a human voice and music to measure the distortion output from their Class C or linear RF stages.

Why cant that be used on SSB? It would be easier to do and a standard voice or music recording would eliminate a lot of discussions over white noise standards.

Carl

There is no standard voice or music. Two tone or pink/white noise are well defined and allow repeatable measurements.


Title: RE: Ham Xcvrs' and Amps', Transmit Spectral Purity, IMD Products, vs. comm/maritime
Post by: KM1H on March 16, 2018, 05:54:20 PM
They are using a standard voice and music (I forget the details) and it seems to work well, you ought to check it out.

Ive used white noise in the early 80's when characterizing the performance of 5-500 mHz CATV style line amps for the Wangnet system. Voice, video, TV, high speed data, long before it became mainstream.

Ive used and been a proponent of it for IMD testing just as long but there is no established standard for ham use.


Title: RE: Ham Xcvrs' and Amps', Transmit Spectral Purity, IMD Products, vs. comm/maritime
Post by: KA4WJA on March 30, 2018, 11:03:57 AM
Well, some may wish that this thread would go away, or at least that I'd not keep adding to it.  :)
But, this is just a brief update, with some disappointing news.

I just finished reading the ARRL Product Review of the Apache Labs ANAN-8000D transceiver (a rig that I was considering buying)....and what a disappointment.  The ARRL reported transmit IMD was only average and the implementation of the Pre-Distortion ("Pure Signal" / "PS") showed only a 5db improvement versus not using it!   (heck, it had significantly better higher-order IMD results when run at 100 watts with NO pre-distortion, versus at its max spec'd 200 watts WITH pre-distortion) {understand this is a 50-vdc LDMOS PA, using an internal DC-DC converter, allowing you to power rig from 13.8vdc @35 amps}

How the ARRL results are so widely different from Adam, VA7OJ/AB4OJ's results, is unknown....and quite disturbing to me...as is the fact that the older ANAN-100D's transmit IMD (w/ pre-distortion) is significantly better...
In the ARRL review, W1TR wrote 2 paragraphs about the pre-distortion and its set-up, commenting on how much easier it is to set-up and calibrate than the ANAN-100D (that he's been using for years)...and since the first ANAN-8000D that they received didn't meet FCC harmonic specs on 6m, they sent it back and received another to test, and since when they find anomalous behavior (as in the transmit IMD tests of the K3S) they contact the manufacturer for input/corrections, so I assume the reviewer/tester both set-up and calibrated the ANAN-8000D's "pure signal" properly and that what they tested was what you get??  :(
I wish I was wrong here....and hope that there was a problem with this ANAN-8000D....but, it appears not??

In fairness to my fellow hams, and to all the other ham rigs identified here, if we're going to use the only source of dozens (actually many 100's, but I only used about 40 or so, here) of transceiver reviews with transmit IMD tested the same way, in the same lab, for decades...then we must use their results...
So...

ARRL Product Tests Results of the Apache Labs ANAN-8000D  (from April 2018 QST)

"typical" results at HF @ 200 watts PEP
-32 / -43 / -52 / -59db(PEP)  WITH Pre-distortion
-30 / -38 / -47 / -54db(PEP)  WITHOUT Pre-distortion


"worst case" result (on 12m) @ 200 watts PEP
-28 / -33 / -42 / - 45db(PEP)   WITH Pre-distortion


On 20m / "typical" @ 100 watts PEP
-32 / -48 / -62 / -76db(PEP)  WITHOUT Pre-distortion


{In their sidebar, the ARRL noted that the ANAN-8000D's transmit IMD was better on the low bands (160m - 40m) than on the higher bands, and commented on the better IMD @ 100 watts out, with the pre-distortion OFF...and suggested that this is fine for use with external power amps, giving you a clean signal...(similar to most maritime HF rigs' PA's, for decades now...not exactly rocket science, designing/building a 200-watt PA and using it at 100 watts... :( }

I know some here eschew the ARRL tests results as too generous, etc., but in this case they are far worse than the test results from the other source....so, while we won't argue the numbers, I assume we can all simply accept that the ANAN-8000D (and its pre-distortion) isn't really measuring-up to its advertised specs....and no matter what the proponents of pre-distortion (I'm one of them, BTW) desire, it just isn't preforming as we'd like, for our hi-power broadband HF transceivers!  
As of early 2018, it appears that it just isn't preforming as a "repeatable" / "mass-production-capable" system....some find it works for them, and some don't....unfortunately that's not a mature / mass-marketable system... :(   (and, while I know some have harped on Flex, for not incorporating pre-distortion into their new rigs, you may now be starting to see that while they'd like to, they have reasons that this isn't a high-priority....not the least of which are "cost-benefit" reasons?)


So, now I think I'm going wait on buying a new rig... :(


73,

John,  KA4WJA


P.S.  Part of me wishes I could go back and edit the (anomalous?) ANAN-8000D's test results, that I posted last month....but maybe it's a good thing to show these varied results??  We can all learn about comparing apples-to-apples..(using the same test lab and procedures, to compare dozens/hundreds of radios....rather than looking elsewhere) :)
Sorry about my impatience!  I should've just waited 'til the ARRL got around to testing / publishing!  :(


Title: RE: Ham Xcvrs' and Amps', Transmit Spectral Purity, IMD Products, vs. comm/maritime
Post by: KM1H on March 30, 2018, 01:55:15 PM
Wattaya  expect for $4K?


Title: RE: Ham Xcvrs' and Amps', Transmit Spectral Purity, IMD Products, vs. comm/maritime
Post by: W3RSW on March 30, 2018, 02:57:33 PM
Given the good results published by others since Pure Signal’s beginning some years ago John, your post may be seen as somewhat alarmist.  Also ARRL’s whole lab report should be read to get a better feel for their perplexity.

You need to go here to understand what’s going on. ARRL will probably correct the test procedure and / or retest the rig.  Apparently there was a publishing deadline among other things including that the rig was manufactured in Australia. 
No one else has gotten such dismal results with pure signal correctly engaged in any Anan SDR.

https://groups.yahoo.com/neo/groups/apache-labs/conversations/topics/34078?reverse=1


Title: RE: Ham Xcvrs' and Amps', Transmit Spectral Purity, IMD Products, vs. comm/maritime
Post by: W3RSW on March 30, 2018, 03:41:53 PM
If you want to see a very comprehensive 8000DLE test report see this one.
Pure Signal enhancement is towards the very end of the report.
IM results without P.S. reasonably match ARRL’s results.

http://www.ab4oj.com/sdr/apache/anan8000dle_notes.pdf

To set minds at ease, several have probably bought the Anan based on this unbiased report.


Title: RE: Ham Xcvrs' and Amps', Transmit Spectral Purity, IMD Products, vs. comm/maritime
Post by: KB2TIS on March 30, 2018, 04:14:42 PM
Well, some may wish that this thread would go away, or at least that I'd not keep adding to it.  :)
But, this is just a brief update, with some disappointing news.

I just finished reading the ARRL Product Review of the Apache Labs ANAN-8000D transceiver (a rig that I was considering buying)....and what a disappointment.  The ARRL reported transmit IMD was only average and the implementation of the Pre-Distortion ("Pure Signal" / "PS") showed only a 5db improvement versus not using it!   (heck, it had significantly better higher-order IMD results when run at 100 watts with NO pre-distortion, versus at its max spec'd 200 watts WITH pre-distortion) {understand this is a 50-vdc LDMOS PA, using an internal DC-DC converter, allowing you to power rig from 13.8vdc @35 amps}

What I find interesting is that when faced with clearly wrong results, they ran the article anyway.

Or you can assume that the community of hams using puresignal are all in a group hallucination.

I'm thinking there are better odds something was wrong with that unit.


Title: RE: Ham Xcvrs' and Amps', Transmit Spectral Purity, IMD Products, vs. comm/maritime
Post by: AC2RY on March 30, 2018, 07:56:00 PM
Well, some may wish that this thread would go away, or at least that I'd not keep adding to it.  :)
But, this is just a brief update, with some disappointing news.

I just finished reading the ARRL Product Review of the Apache Labs ANAN-8000D transceiver (a rig that I was considering buying)....and what a disappointment.  The ARRL reported transmit IMD was only average and the implementation of the Pre-Distortion ("Pure Signal" / "PS") showed only a 5db improvement versus not using it!   (heck, it had significantly better higher-order IMD results when run at 100 watts with NO pre-distortion, versus at its max spec'd 200 watts WITH pre-distortion) {understand this is a 50-vdc LDMOS PA, using an internal DC-DC converter, allowing you to power rig from 13.8vdc @35 amps}



Most people who buy 8000D will never use it as standalone transceiver. Thus IMD at full power is irrelevant - you only need 15-20W to push external solid state amplifier to full power. It that power level IMD of transceiver itself will be negligent.



Title: RE: Ham Xcvrs' and Amps', Transmit Spectral Purity, IMD Products, vs. comm/maritime
Post by: KA4WJA on March 30, 2018, 08:23:22 PM
Rick, W3RSW,
Alarmist??
Because I found test data different than what I myself touted as wonderful, just last month??
And, I've heard other anecdotal reports of wide variations in ANAN rigs' performance....and wanted my fellow hams to know all the facts...
Color me confused...but, no worries my friend... :)

As for the other points...

Thank you, but I'm not only intimately familiar with the ARRL's testing procedures (and have been familiar with them for some 40+ years....and have been keeping myself up-to-date with their changes, and have posted the entire detailed procedure here on eham, etc. etc.), and am also very familiar with the report you cite....(in case you missed the posts from the past couple months, Adam's report was the basis for my consideration of the ANAN-8000D)
And, FYI, in addition to posting Adam's results, I sought and received permission from him to post his spec analyzer image of his test of the 8000D, right here on eham....and did so over a month ago...
(and I was taught about IMD and test procedures back in the mid-1970's....and Carl  and I have already gone 'round 'n round, on these test procedures....and I'm not going thru that again... :) )

BTW, I think Adam is a great guy and don't dispute his results....just commenting on the lack of repeatability in these rigs, making me unwilling to spend my $$$$ (FOUR THOUSAND of them) for a rig whose transmit IMD is beat by the Kenwood TS-590SG!!  :(

Further, I not only read the entire ARRL test report of the 8000D, I read it twice....and when posting here, triple-checked everything and read it all again... :)

Fact is:
It makes no sense!
But, those are the numbers they published!
And, you know what they say.....you dance with the one that brung 'ya to the party!  :)

To be clear, I'm not panning the ANAN....just pointing out this lack of repeatability of results...
This is fine for homebrewed rigs....but not acceptable in multi-thousand dollar production radios...
(If you get a Flex engineer alone, they'll tell 'ya "off-the-record" of their difficulty in making all of this work out of the box....and they want to sell radios that work!!  :) )


~~~~~~~~~~


Brian, KB2TIS, I originally assumed as you....that there was something wrong with that 8000D, and/or the tester didn't know how/what to adjust....and you may be correct...
BUT...
But, since it was ME (and my reputation) that was on the line here on these pages, AND the gist of this thread that we can use the ARRL test results to compare various radios....even if the exact numbers might not conform to what others see as "the proper way to report", they are not only an accurate way to compare different radios, but also the only real, independent test data that we have for 100's of ham transceivers going back 50+ years...
SO..
So, with my words on the line, I wanted to make the actual ARRL test data available as soon as I read it...


73,
John,  KA4WJA


Title: RE: Ham Xcvrs' and Amps', Transmit Spectral Purity, IMD Products, vs. comm/maritime
Post by: KA4WJA on March 30, 2018, 08:38:42 PM
Alex,
Ham radio is a big space....and there's plenty of room for everyone's opinion....
But, perhaps you can see your way to look thru someone else's eyes for a moment??

Most people who buy 8000D will never use it as standalone transceiver. Thus IMD at full power is irrelevant - you only need 15-20W to push external solid state amplifier to full power. It that power level IMD of transceiver itself will be negligent.

If we ignore, for a moment, that I only run a barefoot 150-watt HF rig on my boat....and while I do use my Alpha on summertime 75m, I regularly run my TR-7's barefoot at home...and the tens of thousands of other hams that have the $$$$, but do not own/use an external power amp....well, let's just ignore all of that for a moment...

What you seem to be implying is that if you want to spend $4000 on a "QRP" rig, the ANAN-8000D is a great choice??   'Cuz anyone that really wants more than QRP power will being using an amp??
And, everyone will of course be using a high-gain/low-drive-power amp??? (and a SS amp, of course??)
Seriously, I do understand you correctly...yes??

Well, as I said...there is room for everyone here....and I respect your opinion....
Mine is just different... :)



But, to put a direct point on this...as I just wrote to Brian a few minutes ago:
....since it was ME (and my reputation) that was on the line here on these pages, AND the gist of this thread that we can use the ARRL test results to compare various radios....even if the exact numbers might not conform to what others see as "the proper way to report", they are not only an accurate way to compare different radios, but also the only real, independent test data that we have for 100's of ham transceivers going back 50+ years...
SO..
So, with my words on the line, I wanted to make the actual ARRL test data available as soon as I read it...
What everyone does with that data, is up to them... :)


I assume we can just agree to disagree here....:)


73,  
John,  KA4WJA


Title: RE: Ham Xcvrs' and Amps', Transmit Spectral Purity, IMD Products, vs. comm/maritime
Post by: G3RZP on March 30, 2018, 10:34:57 PM
One difficulty lies in determining the measurement uncertainty. Take conducted output power as an example. To a 95% certainty, it is European and IEC practice below 1 GHz to allow a tolerance of +/-0.75dB. That means that wherever the equipment is tested, one is certain to a 95% probability that the measured output is within +/-0.75dB. But it is all a statistical probability.

Now 0.75dB may seem a lot, but consider such matters as the 95% probability of knowing the loss in the coax connecting cables, the actual impedance of the cables and the VSWR of the load and the accuracy of the power measurement and you can see how it adds up.

Unfortunately, there do not appear to be any amateur radio reviews of equipment that state these parameters, and without a certified test lab, drawing conclusions can be somewhat dangerous. The Anan transceiver was not tested in the UK in a certified lab, but it appeared on several bands to have harmonics in excess of European and international Radio Regulation requirements - which on 6 metres, are 10dB more stringent than the FCC, and on other bands, where at powers above 5 watts,  they are 7dB more stringent than FCC.


Title: RE: Ham Xcvrs' and Amps', Transmit Spectral Purity, IMD Products, vs. comm/maritime
Post by: W3RSW on March 31, 2018, 05:36:25 AM
Several of we amateurs have already mentioned the possibility of a defective 8000 being tested by the ARRL , including similar reference to the missing feedback loop in the output of a 200 D causing distortion.

All these concerns and many more were hashed out in the Anan Yahoo threads “widely read by  SDR users everywhere.”   ;D. Those reading it and similar as extensively as purported would already know the possibility of a defective unit from Anan and simply sent the unit back for a replacement. So yes, pretty inconvenient and not the hallmark of a multimillion dollar outfit.  — of which Apache Labs, a very small Indian company isn’t, but is a very helpful company which originally just built in volume TAPR’s Hermes boards and expanded to more advanced products from there, a tremendous additional service to the amateur community.  Apache’s product helped force other manufactures to acknowledge the rise of DDC SDR’s.

It’s to bad the ARRL’s findings of a non full page advertiser’s product were hurried out the door by a frustrated lab tech that clearly, petulantly perhaps, knew that a few Pure Signal dB differences were not the major dB differences that were reported by all others, products beyond the 9th withstanding but the publication of such would express his ire.  ;D. - - speculation only, but one wonders.


Title: RE: Ham Xcvrs' and Amps', Transmit Spectral Purity, IMD Products, vs. comm/maritime
Post by: AC2RY on March 31, 2018, 08:59:55 AM

It’s to bad the ARRL’s findings of a non full page advertiser’s product were hurried out the door by a frustrated lab tech that clearly, petulantly perhaps, knew that a few Pure Signal dB differences were not the major dB differences that were reported by all others, products beyond the 9th withstanding but the publication of such would express his ire.  ;D. - - speculation only, but one wonders.

If Apache Labs worries about PR, they should ask ARRL to send them tested unit back for evaluation. If it will be found to be defective, then ARRL should get a new unit tested again and follow up review published again, and Apache Lab apologize for QC missing the faulted unit. That is a common practice for other (non-HAM related) product reviews.


Title: RE: Ham Xcvrs' and Amps', Transmit Spectral Purity, IMD Products, vs. comm/maritime
Post by: KM1H on March 31, 2018, 09:23:48 AM
Quote
If Apache Labs worries about PR, they should ask ARRL to send them tested unit back for evaluation. If it will be found to be defective, then ARRL should get a new unit tested again and follow up review published again, and Apache Lab apologize for QC missing the faulted unit. That is a common practice for other (non-HAM related) product reviews.

The ARRL has done that for decades


Title: RE: Ham Xcvrs' and Amps', Transmit Spectral Purity, IMD Products, vs. comm/maritime
Post by: KA4WJA on March 31, 2018, 09:33:37 AM
Rick, W3RSW,
I was working at a client's office this morning (yes, on a holiday weekend), and was hoping you didn't read my posting from late last night until I had a chance to apologize / modify it!! :)
I'm sorry if my words came off as abrupt or in any way less than friendly!!  Definitely not my intention! (a bad night!)

So, with that said...
I thank you for the info about defective ANAN-8000's...
I was not aware of that!
And, I do thank you for this info...

Many of us who are not into SDR, might not be aware of these issues, as I was not.
Do you know if Terry, W1TR (who did the ARRL product test / review of the ANAN-8000D, and who has owned / used an ANAN-100D for a few years), was aware of these problems??
If he was, it seems odd that they would've proceeded with a test / review of a rig that is not ready for the mass market??, so I assume he was not aware of these issues??


And, as for the 200D issue??
I assume that is another reference to someone on the yahoo group?  As the ARRL never published a review of the 200D, just the 100D and now the 8000D (and their PiHPSDR Controller)...

And, please note that I too appreciate Apache Labs, and their work....it's just that I'm past the "tinkering phase" (built my first 3-watt tube CW transmitter in mid-70's, a single 811a amp, a dual 811a amp, many heathkits including my SB-221 that is still running strong at my best friends house ` 38 years and going! and countless other projects)....and, I'm NOT a software guy, NOT an IT guy...I'm a radio guy! 
Yes, I'm aware it is 2018, and darn near everything has a processor in it, and some software is needed to make it all work....but, I'm NOT a software guy, and I'm not going to be one....so, if I'm going to buy a Software Defined Radio, it better work, work right-out-of-the-box, and it better not need me to return the darn thing to the factory!!   Seriously??
I've got both old-fashioned HF rigs, modern 21st Century IF-DSP HF rigs, amps, keyers, etc. etc. etc. etc...and in over 40 some years, none have ever been back to the factory for repair!! 
(okay, I bought my Alpha 77 from a guy who had it checked-out and certified at the Alpha factory before he put it up for sale....and Molly and Glenn were nice enough to give me a run down on it....and there was a guy at RL Drake Service that sold me a couple minor parts about 20 years ago, that I could've gotten elsewhere....but that's all the "factory service" I've ever needed...)

If I going to spend my money on a new rig, my criteria is:  excellent transmit IMD, and reliability...(and certainly that it works, right out-of-the-box!)

That's not to say that there isn't a role for SDR in ham radio, there is!  (look at Flex)
But, in my opinion, ANAN just isn't quite ready for the mass market...yet!
Yes, if you wish to spend the time and effort joining / reading thru a Yahoo group, in order to understand and troubleshoot a homebrew issue or get help with a 50 - 70 year old Hallicrafters, etc...that's great....
But, to spend $4000 on a new radio and then have to do that??  Not really what I would consider a "market ready" product.....and assume we'd all agree with that??


If Terry, W1TR, hadn't mentioned in his review of the 8000D that he had owned/used an ANAN-100D for a few years, and further commented on the ease of setting-up and calibrating the "Pure Signal" on the 8000D, I would agree with you that it was likely lab tester error....
But, it's certainly a strange occurrence!!  
(and one that has cost Apache Labs at least one sale of an 8000D...me!


73,

John,  KA4WJA




Title: RE: Ham Xcvrs' and Amps', Transmit Spectral Purity, IMD Products, vs. comm/maritime
Post by: AC2RY on March 31, 2018, 10:30:29 AM
Rick, W3RSW,
I was working at a client's office this morning (yes, on a holiday weekend), and was hoping you didn't read my posting from late last night until I had a chance to apologize / modify it!! :)
I'm sorry if my words came off as abrupt or in any way less than friendly!!  Definitely not my intention! (a bad night!)

So, with that said...
I thank you for the info about defective ANAN-8000's...
I was not aware of that!
And, I do thank you for this info...

Many of us who are not into SDR, might not be aware of these issues, as I was not.
Do you know if Terry, W1TR (who did the ARRL product test / review of the ANAN-8000D, and who has owned / used an ANAN-100D for a few years), was aware of these problems??
If he was, it seems odd that they would've proceeded with a test / review of a rig that is not ready for the mass market??, so I assume he was not aware of these issues??


And, as for the 200D issue??
I assume that is another reference to someone on the yahoo group?  As the ARRL never published a review of the 200D, just the 100D and now the 8000D (and their PiHPSDR Controller)...

And, please note that I too appreciate Apache Labs, and their work....it's just that I'm past the "tinkering phase" (built my first 3-watt tube CW transmitter in mid-70's, a single 811a amp, a dual 811a amp, many heathkits including my SB-221 that is still running strong at my best friends house ` 38 years and going! and countless other projects)....and, I'm NOT a software guy, NOT an IT guy...I'm a radio guy! 
Yes, I'm aware it is 2018, and darn near everything has a processor in it, and some software is needed to make it all work....but, I'm NOT a software guy, and I'm not going to be one....so, if I'm going to buy a Software Defined Radio, it better work, work right-out-of-the-box, and it better not need me to return the darn thing to the factory!!   Seriously??
I've got both old-fashioned HF rigs, modern 21st Century IF-DSP HF rigs, amps, keyers, etc. etc. etc. etc...and in over 40 some years, none have ever been back to the factory for repair!! 
(okay, I bought my Alpha 77 from a guy who had it checked-out and certified at the Alpha factory before he put it up for sale....and Molly and Glenn were nice enough to give me a run down on it....and there was a guy at RL Drake Service that sold me a couple minor parts about 20 years ago, that I could've gotten elsewhere....but that's all the "factory service" I've ever needed...)

If I going to spend my money on a new rig, my criteria is:  excellent transmit IMD, and reliability...(and certainly that it works, right out-of-the-box!)

That's not to say that there isn't a role for SDR in ham radio, there is!  (look at Flex)
But, in my opinion, ANAN just isn't quite ready for the mass market...yet!
Yes, if you wish to spend the time and effort joining / reading thru a Yahoo group, in order to understand and troubleshoot a homebrew issue or get help with a 50 - 70 year old Hallicrafters, etc...that's great....
But, to spend $4000 on a new radio and then have to do that??  Not really what I would consider a "market ready" product.....and assume we'd all agree with that??


If Terry, W1TR, hadn't mentioned in his review of the 8000D that he had owned/used an ANAN-100D for a few years, and further commented on the ease of setting-up and calibrating the "Pure Signal" on the 8000D, I would agree with you that it was likely lab tester error....
But, it's certainly a strange occurrence!!  
(and one that has cost Apache Labs at least one sale of an 8000D...me!


73,

John,  KA4WJA




Software defined radio like any computer today needs "software upgrades" to fix newly found problems. IC-7300 so far has 5 new versions of code, and IC-7610 already has 4. What Apache labs is missing - officially published Wiki with information extracted from users' groups with comments from their own support engineers.

I recall my first sport car with advanced type of motor, which I bought in 2004: for the first two years of service engine computer software was updated almost every 3 month. I didn't complain back then - just enjoyed driving that beast.



Title: RE: Ham Xcvrs' and Amps', Transmit Spectral Purity, IMD Products, vs. comm/maritime
Post by: K6AER on March 31, 2018, 10:31:24 AM
I would love to see the test lash up the ARRL used for the testing. It cannot be that difficult to generate a low distortion two tone audio signal for the test results. The only other thing is the spectrum analyzer being kept in the linear region.


Title: RE: Ham Xcvrs' and Amps', Transmit Spectral Purity, IMD Products, vs. comm/maritime
Post by: KA4WJA on March 31, 2018, 10:56:33 AM
Mike,
Yep, the ARRL lab can generate a couple clean tones and easily keep the analyzer reading in its linear range.

So, the answer to your question, in brief, is here in reply #109...from just last month..
https://www.eham.net/ehamforum/smf/index.php/topic,97093.msg1053842.html#msg1053842

And, all the details can be found in this paper here:
http://www.arrl.org/test-procedures-manual

(and I think there was a QST article a few years back about the ARRL lab and its equipment, and tests, etc.???)
I would love to see the test lash up the ARRL used for the testing. It cannot be that difficult to generate a low distortion two tone audio signal for the test results. The only other thing is the spectrum analyzer being kept in the linear region.


A screw-up in the ARRL lab seems like an obvious answer to the conundrum of why the pre-distortion doesn't work well on that ANAN-8000D, and this just might be it...BUT...
But, with Rick's mention that there are known issues with the 8000D, and other ANAN's, and some (many??) defective units shipped, I'm still thinking this is a rig not quite ready for market...


73,
John,  KA4WJA


Title: RE: Ham Xcvrs' and Amps', Transmit Spectral Purity, IMD Products, vs. comm/maritime
Post by: AC2RY on March 31, 2018, 10:57:59 AM
I would love to see the test lash up the ARRL used for the testing. It cannot be that difficult to generate a low distortion two tone audio signal for the test results. The only other thing is the spectrum analyzer being kept in the linear region.

ARRL should afford to have NIST traceable certification for measuring gear they use. And I hope their staff knows how to use it.


Title: RE: Ham Xcvrs' and Amps', Transmit Spectral Purity, IMD Products, vs. comm/maritime
Post by: G3RZP on April 01, 2018, 05:45:23 AM
Does the NIST certification list the measurement uncertainty?


Title: RE: Ham Xcvrs' and Amps', Transmit Spectral Purity, IMD Products, vs. comm/maritime
Post by: W3RSW on April 01, 2018, 10:57:35 AM
Quote
Do you know if Terry, W1TR (who did the ARRL product test / review of the ANAN-8000D, and who has owned / used an ANAN-100D for a few years), was aware of these problems??

John, don’t know his thoughts or previous experience, but feel he’s probably visited the Anan Yahoo site I’ve previously referenced along with on line manuals for the 100D.
You’ll have to ask him.

There are 64 posts on the ARRL 8000DLE test alone on that Yahoo site; several previous questions on this board already answered for all to read. —Some quite hot, some quite rational. (Don’t have to join Yahoo site to read, just to post or answers, etc. ). One answer has the 8000 in question being sent back to “Doug” for examination, so looks like retesting, re-radioing, re-editing or various combinations will be forthcoming.

I wrote the 200d missing feedback loop note in that series of 64, referencing an even earlier thread complete with pictures of a missing single feedback wire running through the output ferrite, ‘one turn’ winding.  I’m oldalcoa on that board, sometimes remembering to add my name and call letters, but TMI.  ;D


Title: RE: Ham Xcvrs' and Amps', Transmit Spectral Purity, IMD Products, vs. comm/maritime
Post by: VK3BL on April 04, 2018, 03:26:27 PM
I would love to see the test lash up the ARRL used for the testing. It cannot be that difficult to generate a low distortion two tone audio signal for the test results. The only other thing is the spectrum analyzer being kept in the linear region.

It isn't.

The free program 'Audacity' for Windows, Mac & Linux has a built in tone generator.

All you need to do is:
1) [Tracks] Add a track
2) [Generate] Generate a tone

Just remember PEP applies, so you will need to adjust amplitude based on your quantity of tones.  1 tone = 0.9, 2 tones = 0.45 each, you get the idea :)

This is how I generate tone sets for radios I test, and with a lot of radios now having built in sound cards, there is often no need to even worry about the "mechanics" of injecting two single tones :)

The ANAN software actually comes with built in 2 tone generation as well.

With cheap devices such as the SDRPlay, there has never been a better time to add one to your shack (along with a computer, RF Sampler and Dummy Load) and perform your own IMD Testing.

You learn a lot.  For example, the Yaesu FT-81X series can be incredibly linear in HF at less than rated output, something I wasn't expecting.  That said, it makes sense given the amount of negative feedback designed so that a single set of power FETs can cover a >10:1 octave range!

The two 'learnings' that really stuck with me are just how quickly IMD rolls off after the first 3dB or so of output reduction, and how the distortion product percentages change.  E.g., at flat out, IMD5 will usually be most dominant, whilst at 50% IMD 3 & 5 will often be about even, and below 50% IMD 3 dominates till they all disappear.

I really encourage anyone who hasn't seen it for themselves to check out my video here; I really do hope seeing IMD measured opens your eyes the way it did mine the first time I saw it for myself:
https://youtu.be/Sc_6ST5NK3k (https://youtu.be/Sc_6ST5NK3k)

73, Jarrad


Title: RE: Ham Xcvrs' and Amps', Transmit Spectral Purity, IMD Products, vs. comm/maritime
Post by: KA4WJA on April 04, 2018, 05:25:43 PM
Jarrad,
1)  I will let Mike speak the details for himself... :)
But, since he's a professional RF engineer (who I believe did the certification testing of some recent Alpha amps), I interpreted his comment as frustration at possible ARRL's editorial (or even technical) ineptness, not as a question of how to generate two clean tones and keep the analyzer in the linear range.  :)  And, pretty sure he knows how to read PEP during a two-tone test.  :)
{probably just us yanks and you Aussies separated by a common language?? :) }


2)  But, more importantly (and directly on-point of this whole discussion) is congrats to you for finding on your SDR what we've been discussing here...
Fact is, when you see rapid / large reduction in IMD products with just small decreases in output, you are seeing exactly what I originally started this thread about!  The non-linearity of our ham radio transceivers' PA's....especially when operated at their "advertised" output...

Our "100 watt" ham rigs, if sold/marketed to the "CB Radio" universe, would be advertised as "200 watt" or "250 watt" radios!!  And, in the commercial / maritime market would probably be "50 watt" exciters!!

Fact is, if you're seeing rapid / large increases in IMD with small increases in output, the PA is not really operating linearly.  And, depending on the exact power output and the particular PA you're looking at, you're probably in gain compression, too!
But...

But, remember the solution is not quite as simple as just running the rig at "half power" or "70% power", etc....'cuz the design and biasing of the PA needs to be taken into account...
And, this is THE premise of this whole discussion here...
Some of the same manufacturers that make our ham rigs, also make commercial and maritime rigs, and they design these PA's differently!!  They are designed using devices that would normally be thought of being used in "200 to 250 watt ham rigs", but are designed to be 150 watt PA's...
And, they are biased as linearly as possible, but still in AB (not Class A)....



3)  The second thing that you notice is the variances of 3rd, 5th, and higher order products...at various drive / output powers...(assuming the analyzer is being used well into the linear region...'cuz, I've seen some weird results when I forgot to adjust an attenuator, etc....Oppss!)
This was also brought up (briefly) in this discussion....both in the way that a specific PA can be designed and biased to bring higher order products down, whilst sacrificing the 3rd order products, etc., and vice versa...and...
And, also in that as you vary the drive to a PA, this changes the PA's linear response and hence you can change the biasing....this needs to be taken into account....(this is one of the things that the Eimac paper mentions prominently...and something that it took me a few years to grasp, back 40 years ago.)
Sorry if I didn't highlight this more....I think I only brought this up briefly, and probably while Carl and I were off on our rants...so, probably lost in the dust!  :)

But, in a nutshell, when you see the various IMD products move up / down independently (asymmetrically) from each other, as you are changing the drive power / output power of the PA, you are seeing one of the situations that I was referring to when referencing the warning from the Eimac paper...(they were warning that some can find "sweet spots" in various PA designs, at various power levels / various biasing, where some products are lower than others, and others at other drive and biasing levels...and that we should look closely at advertised specs / test results)....and this is one reason why I'd like to actually see the analyzer scans (not just the reported 3rd, 5th, 7th, and 9th products), and especially be able to see the products out well past the 11th and 13th product...as well as have the ARRL do / publish "expanded test results" for all transmitters and amps, where they show results at various drive levels and output levels...(not sure they have the time to do these anymore, but I really liked 'em when the did them!)

Here is just a snippet of what I wrote last month...
 

http://www.cpii.com/docs/related/22/C&F4Web.pdf

Eimac, also warns against drawing conclusions about amplifier IMD based solely of tests at max drive power, as "maximum intermodulation distortion does not necessarily occur at maximum drive.....plots of IMD level (Y axis) referred to the driving signal expressed as a ratio of drive to operating bias. As the drive is increased, the various IMD products pass through maxima and minima. Misleading conclusions of amplifier performance may be drawn if the equipment happens to be tested near cusp on the IMD curve, where a particular product drops to an extremely low level. The whole operating range of the equipment must be examined to draw a true picture of IMD performance." But, this is about variations in curves based on drive power and operating bias. (not about the freq or spacing of the "tones")  Meaning that at various drive levels, different bias levels can be used to show different IMD levels, just as I mentioned weeks ago, where I wrote about PA design / biasing (and tuning) can be done to reduce some IMD products at the expense of increases in other IMD products, and how that can change with various drive levels...(whether we're talking about tube PA's and using Eimac words...or referring to SS PA's and using Motorola words, etc. etc. etc...the physics doesn't change...:) )




4)  As for using soundcards to generate "clean" tones....and SDR's used as spec analyzers???
I have no experience with these...and guess I'm just old fashioned, as I just don't see this as a proscribed scientific testing procedure....but, I could be wrong!  :)
I just don't know how anyone can be sure of that their SDR is "in cal"....lad test gear gets re-cal'd every 6 to 12 months, and how can a piece of consumer software and a couple A/D codecs be "cal'd"??
But, like I say....I could be wrong here??



Again Jarrad, congrats to seeing what we've been talking about!!  :)

73,
John,  KA4WJA


Title: RE: Ham Xcvrs' and Amps', Transmit Spectral Purity, IMD Products, vs. comm/maritime
Post by: AA4HA on April 04, 2018, 07:16:48 PM
Some of the same manufacturers that make our ham rigs, also make commercial and maritime rigs, and they design these PA's differently!!  They are designed using devices that would normally be thought of being used in "200 to 250 watt ham rigs", but are designed to be 150 watt PA's...
--------------
4)  As for using soundcards to generate "clean" tones....and SDR's used as spec analyzers???
I have no experience with these...and guess I'm just old fashioned, as I just don't see this as a proscribed scientific testing procedure....but, I could be wrong!  :)
I just don't know how anyone can be sure of that their SDR is "in cal"....lad test gear gets re-cal'd every 6 to 12 months, and how can a piece of consumer software and a couple A/D codecs be "cal'd"??
I am glad to see that this thread is going full circle back to the original premise:
At least two of the "big three" in ham radio manufacturing also make commercial products that are designed much more conservatively than their amateur radio products. One company has an aviation line and the other is involved with marine and commercial (IDK about Kenwood ATM). They are capable of coming up with cleaner implementations to meet other parts of Title 47 (FCC) and EU standards but for some reason that is not carrying forward in to their amateur radio lines.

It has been argued that a better design to meet spec would make amateur radio equipment unaffordable but the money spent on design is not as significant. If two or three engineers spent an additional two or three days in design that is a small number when spread across a few thousand radios in a design that may carry forward for ten years. Additionally, much of what they have already done on their commercial products can be copied right over; Maritime HF and amateur radio HF are still in the 2-30 MHz band.

---------------
The second quote I pulled for reference is in regards to the lab equipment to test bench radios: From what I have seen in articles put out by ARRL over the years they have a pretty comprehensive lab with good gear. Performing testing of RF specifications is very methodical and you repeat the same tests repeatedly to validate the results. Maybe they had something set incorrectly in the test setup, maybe something was misaligned, every other RF engineer I have worked with was usually willing to share their entire configuration and methodology to people of similar capability. We want our results to be repeatable. In fact, if you are testing for product compliance it has to be repeatable or as a certification lab or manufacturer you can face some hefty fines by the regulatory agencies.

I would not be relying upon a computer generated set of tones or an SDR for testing; That is fine if you want to verify that the testing done by others approximately matches yours but it is not definitive. There are too many things that happen in gear that it is not designed around a test environment. Even with audio tones you have strange things that happen that do not show up at first glance with a frequency counter, voltmeter or oscilloscope.


Title: RE: Ham Xcvrs' and Amps', Transmit Spectral Purity, IMD Products, vs. comm/maritime
Post by: KM1H on April 05, 2018, 11:40:30 AM
The ARRL full testing procedure is on their website.

Carl


Title: RE: Ham Xcvrs' and Amps', Transmit Spectral Purity, IMD Products, vs. comm/maritime
Post by: G0HZU on April 05, 2018, 02:42:03 PM
Quote
I just don't know how anyone can be sure of that their SDR is "in cal"....lad test gear gets re-cal'd every 6 to 12 months, and how can a piece of consumer software and a couple A/D codecs be "cal'd"??
But, like I say....I could be wrong here??

I can't comment on SDRs but many of the close in distortion measurements are relative so something like a decent soundcard (with a downconverting mixer ahead of it) is going to be much better in terms of log accuracy compared to the very best $$$ flagship spectrum analysers from 30-40 years ago from HP etc. This applies even if the $$$ analyser just came back from calibration. It should be possible to double check the log accuracy of a soundcard using a decent step attenuator and the step attenuator can be tested with a decent multimeter at a few kHz. Or a decent DAC could be used to check the soundcard log range. All of this could be done at home by a keen ham.

The log accuracy should check out to be way better than you would need for testing a ham radio for close in IMD on a two tone test. If it doesn't then you can always try another soundcard.



Title: RE: Ham Xcvrs' and Amps', Transmit Spectral Purity, IMD Products, vs. comm/maritime
Post by: W3RSW on April 06, 2018, 08:40:30 AM
For DDC SDR's using for example the LTC 2208-16 ADC as found in Anan's, QS1R, etc., the least significant bit error is specified in the data sheet over a wide range. 

This is decent technology now superceeding precise lab equipment of just a decade or so ago, as others have previously mentioned in this thread. Relative IM products are certainly displayed much better using the more modern GUI's, following massaged, more convient bandwidths (by decimation, filters, etc.).


Title: RE: Ham Xcvrs' and Amps', Transmit Spectral Purity, IMD Products, vs. comm/maritime
Post by: AC7CW on April 06, 2018, 09:07:32 AM
Soundcards are the [very] weak link in measurements. At the low audio spectrum they can have unflat passbands measuring in the tens of db. They don't couple DC at all and the rollup starting at DC to the mid-audio frequencies is ridiculously not flat. They can have huge gain spikes at specific frequencies anywhere in the audio spectrum. At best they are ok for teeny-boppers to listen to crappy music... the rolloff above 20khz is a given of course. I wouldn't use a soundcard for any type of measurements, in fact it bothers me that my SDR rig works into a soundcard. I've searched for an appropriate substitute and afaik it doesn't exist. I'd like to build something on a card that plugs into a computer mobo directly with a DC to 500kHz flat passband, integrated with GPU processing but a project like that is way over my head...



Title: RE: Ham Xcvrs' and Amps', Transmit Spectral Purity, IMD Products, vs. comm/maritime
Post by: G0HZU on April 06, 2018, 09:46:42 AM
It's easy to avoid the crappy 'no brand' soundcards and still get something fairly decent for a low price.
Even the basic soundcards in my laptop and netbook have a flatness of less than +/-0.2dB across 200Hz to 19kHz. The cheapo netbook is probably +/- 0.1dB over this range.

When it comes to log accuracy over about a 70dB range you can expect the soundcard to be better than +/- 0.1dB the whole way down. You can't get that log accuracy with an $85k spectrum analyser from HP from 30 years ago (I've got several $$$ RF spectrum analysers here from that era).

Another option is the Analog Discovery 2 module as it will give more bandwidth (but it's only 14 bit) I've got one here but I don't use it much. I keep meaning to upgrade the SW for it but it should be fairly good up to about 5MHz. However, I've not done any tests on it for flatness or log accuracy. I'd expect it to be quite good.




Title: RE: Ham Xcvrs' and Amps', Transmit Spectral Purity, IMD Products, vs. comm/maritime
Post by: KA4WJA on April 06, 2018, 04:07:45 PM
Tisha, et al,
Yeah, I'm trying to get things back on track... :)

And, while there may be some hams that wish to discuss sound card quality / accuracy, etc. (as well as the fun things they do with their analyzers, etc.), perhaps those that do will start their own thread about all of that...
But, please guys let's try to stay on topic, here. :)

73,
John,  KA4WJA


Title: RE: Ham Xcvrs' and Amps', Transmit Spectral Purity, IMD Products, vs. comm/maritime
Post by: G0HZU on April 06, 2018, 05:25:38 PM
The other reason I suggested the use of soundcards was because they are going to be a much faster tool compared to the old/basic analysers used on the first page on this thread. Take a look at the old HP analyser with the 40kHz span. It takes 12 seconds to sweep the span. It  wouldn't be able to cope with the fast changes associated with real human speech. Ideally, one would want to assess how the radio behaves when driven by a typical operator with a microphone. That old thing would be hopeless for this. Maybe it's time for the various testers to ditch these older analysers for something modern and fast. It doesn't have to be a sound card, some modern VSA type analysers are very fast and can capture a test transmission in real time for playback/analysis on a computer.

You might find that when real world tests like this are done with real speech you will see a bigger difference between a good radio and a bad one. A static two tone test is a classic test but the person who benefits most from it is the person doing the test because they can see how the IMD terms change with drive level and choice of test tone frequency. Nearly all of that info is lost once you produce a single screenshot for a test report. A modern test method could provide IQ test results data in a file format for various arbitrary test waveforms at various drive levels.


Title: RE: Ham Xcvrs' and Amps', Transmit Spectral Purity, IMD Products, vs. comm/maritime
Post by: AC2RY on April 06, 2018, 10:12:58 PM
Soundcards are the [very] weak link in measurements. At the low audio spectrum they can have unflat passbands measuring in the tens of db. They don't couple DC at all and the rollup starting at DC to the mid-audio frequencies is ridiculously not flat. They can have huge gain spikes at specific frequencies anywhere in the audio spectrum. At best they are ok for teeny-boppers to listen to crappy music... the rolloff above 20khz is a given of course. I wouldn't use a soundcard for any type of measurements, in fact it bothers me that my SDR rig works into a soundcard. I've searched for an appropriate substitute and afaik it doesn't exist. I'd like to build something on a card that plugs into a computer mobo directly with a DC to 500kHz flat passband, integrated with GPU processing but a project like that is way over my head... R



Are you serious? Mainstream sound cards are ruler flat up to from 10Hz to 90 kHz. Distortion levels are below -100dB for full range signal. And dynamic range is 110 dB or more.

This is well above anything avalable 20 years ago regardless of cost.


Title: RE: Ham Xcvrs' and Amps', Transmit Spectral Purity, IMD Products, vs. comm/maritime
Post by: G0HZU on April 07, 2018, 02:35:21 PM

I'm not sure if the whole thread should be taken that seriously TBH. One or two claims in the first post seems to be off the planet. I've not been near let alone used an Icom M-700pro marine radio but looking at pictures of it, it just seems to be a basic HF radio aimed at marine use. It looks like it runs from 13.8V so it's probably going to have similar IMD performance to ICOM ham (13.8V) radios of a similar era. It might be tweaked to be slightly better but it's going to be a push pull BJT PA running in class AB. So I'd expect average IMD performance from a radio like that. The ham versions only run 100W PEP so it doesn't make sense that the marine version at 150W PEP will achieve IMD much different to the ham version.

KA4WJA is suggesting that it can suppress all two tone IMD terms to better than -75dB when operated at 150W PEP which is not realistic for a radio like this. Where did the data come from that supports this -75dB IMD claim?


Title: RE: Ham Xcvrs' and Amps', Transmit Spectral Purity, IMD Products, vs. comm/maritime
Post by: AC7CW on April 07, 2018, 06:05:43 PM
Soundcards are the [very] weak link in measurements. At the low audio spectrum they can have unflat passbands measuring in the tens of db. They don't couple DC at all and the rollup starting at DC to the mid-audio frequencies is ridiculously not flat. They can have huge gain spikes at specific frequencies anywhere in the audio spectrum. At best they are ok for teeny-boppers to listen to crappy music... the rolloff above 20khz is a given of course. I wouldn't use a soundcard for any type of measurements, in fact it bothers me that my SDR rig works into a soundcard. I've searched for an appropriate substitute and afaik it doesn't exist. I'd like to build something on a card that plugs into a computer mobo directly with a DC to 500kHz flat passband, integrated with GPU processing but a project like that is way over my head... R



Are you serious? Mainstream sound cards are ruler flat up to from 10Hz to 90 kHz. Distortion levels are below -100dB for full range signal. And dynamic range is 110 dB or more.

This is well above anything avalable 20 years ago regardless of cost.

Please, suggest some products here, I am looking for the path forward to replace my current soundcard.


Title: RE: Ham Xcvrs' and Amps', Transmit Spectral Purity, IMD Products, vs. comm/maritime
Post by: G4ZOW on April 07, 2018, 11:03:10 PM
Choose the features required then click the left hand menu for full spec: http://www.marian.de/en/products/comparison

Matches or improves on anything AudioScience or Digigram have to offer.

The AD2 is my chosen weapon.

All cards are PCIe and DC coupled and with distortion down to -140db & dynamic range 144dB (A).

US distributors in CA & IN.

David G4ZOW/5B4


Title: RE: Ham Xcvrs' and Amps', Transmit Spectral Purity, IMD Products, vs. comm/maritime
Post by: G3RZP on April 08, 2018, 12:30:51 AM
G0HZU,

The standards for marine transceivers are in the ETSI Standards, FCC regs and the international Radio Regulations: they are probably in Japanese and Korean regulations, too. Certainly in Europe - I don't know about the US -  a manufacturer can self certify, but does need to have an adequate quality assurance method, usually assumed to be demanding ISO 9000 compliance.

400 watt and above transceivers historically needed to be able to work full duplex, receiving in the same band: the duplex split varied between bands.



Title: RE: Ham Xcvrs' and Amps', Transmit Spectral Purity, IMD Products, vs. comm/maritime
Post by: SM0AOM on April 10, 2018, 10:22:02 AM

 It looks like it runs from 13.8V so it's probably going to have similar IMD performance to ICOM ham (13.8V) radios of a similar era. It might be tweaked to be slightly better but it's going to be a push pull BJT PA running in class AB. So I'd expect average IMD performance from a radio like that. The ham versions only run 100W PEP so it doesn't make sense that the marine version at 150W PEP will achieve IMD much different to the ham version.

KA4WJA is suggesting that it can suppress all two tone IMD terms to better than -75dB when operated at 150W PEP which is not realistic for a radio like this. Where did the data come from that supports this -75dB IMD claim?


A previous employer used scores of the Icom M-700TY as drivers for higher powered HF amplifiers. Their output power levels were set about 60 to 70 W. The IM3 requirement was better than -32 dB and an averaged voice loading adjacent channel suppression of about -50 dB for the whole system. Stand-alone,they provided about -36 dB IM3.

The ISB rated 1kW transmitters we used provided -42 dB IM3 and -60 dB adjacent channel. This was using exciters that were better than -55 dB IM3 at the 100 mW level.All IM3 figures are referred to one tone, not the inflated ARRL figures.

A post-power amplifier IMD3 of -75 dB is completely unrealistic with conventional means,and hardly realisable even with SDR and digital linearisation techniques.

There is some current research going on here by SM5HP, former developement manager for HF products at ITT-Standard Radio, using "notched noise" and SDR receivers to evaluate the distorsion properties of current both amateur and professional gear.

It turns out that the transfer functions of LDMOS amplifier chains tend to favour higher-order IM products,compared to bipolar amplifier  chains. If driven near their power limits, the newer LDMOS amplifiers show quite pronounced "shoulders" quite far from the desired channel.

This research will continue, including more HF/SSB transmitter chains of different makes and vintages,and is intended to result in a paper about the real-life transmitter adjacent channel and co-location performance that will be presented at the 2019 Nordic HF Conference next summer.


Title: RE: Ham Xcvrs' and Amps', Transmit Spectral Purity, IMD Products, vs. comm/maritime
Post by: KA4WJA on April 10, 2018, 10:56:09 AM
Okay, guys....thanks for pointing out a typo of mine that I made almost 4 years ago.. :)
Until this afternoon, almost 4 years hence, I did not realize I had made this typo / error!!

What I thought I wrote in regards the old M-700Pro, was that "all higher-order IMD products down better then 75db" (meaning products higher than the 9th order...such as 11th, 13th, 15th, etc...)
Sorry, about the "typo" / "omission" of that critical point!!  :(
{BTW, how come nobody else caught this???  'cuz, even Zenki would cry BS on a IMD3 of -75db!!  :) And, certainly anyone that reads this whole thread could see that this must have been a typo / error!!}

But, even more impressive is the fact (sorry I don't have the scans to "prove" it) that a couple older "12 volt" HF marine transceivers, have even BETTER transmit spectral purity and even lower transmit IMD products....
Such as the Icom M-700Pro (which is a 1990's design, that just ceased production about 7 - 8  years ago, and retailed for ~ $1250...and can be purchased used nowadays for about $500 - $700) had even lower phase noise, and all IMD products down better than 75db...and here again, this is at 150 watts PEP output continuous-duty (FSK/SSB/CW)..

To be honest, I read / proof-read the posting....but when you just got done writing something, sometimes what is in your head is what you think you just read!  
Opps...
Sorry about this!


While as I stated, I don't have the scans of the IMD tests of the M-700Pro, my understanding is that the M-700Pro was built to the old Part 80 standards:

(http://i61.tinypic.com/231pi1.png)


And, the only high-order (above 9th order) IMD spec that I found was a reference to the "higher-order products better than 75db down", from an NTIA page years ago...
If I can find it, I'll post it...
But, for certain a well-designed HF rig can have its higher order products down better than 75db at 100 - 150 watts PEP....it's not rocket science.  :)


Again, sorry about the typo!!
But, FYI to all, a simple typo / omission does NOT did-allow all the other factual info I posted, nor the last 4 years of discussing the dismal state of our modern HF ham rigs' transmit IMD!!

And, while I realize that in ISB service, esp SSB/FSK ISB service the IMD3 spec is crucial....in our ham band SSB service, I find the 5th, 7th and higher order products from many of my fellow hams' transmitters to be the most offending, causing the majority of splatter....not to mention the horrible ALC systems causing lots of spurts and sputters (along with the poor IMD splatter)...
Hmm??
I just wrote some "down-home" tech terms that might not translate well internationally....spurts and sputters are of course not engineering terms, but do aptly describe the results on-the-air... :)
So, for those of you that are not USA-based, please be kind to my casual-yankee speech!  :)



73,
John,  KA4WJA


P.S.  Those that wish to further discuss SDR's and soundcards, I will gladly read and learn from you!!!
But, please start your own thread on those topics!  :)
Thanks!!  :)
  


Title: RE: Ham Xcvrs' and Amps', Transmit Spectral Purity, IMD Products, vs. comm/maritime
Post by: ZENKI on April 17, 2018, 03:27:00 AM
When the FCC was in the business of engineering and developing real engineering standards the IMD requirements were most demanding in the world. In particular the OLD Part 80 FCC Marine and Commercial HF SSB IMD standard.

The FCC place more importance on higher order  IMD products that had to be suppressed to the highest levels, IMD products from the 11th order and above.  I cant exactly remember but the formula was very simple. 10log the transmitter power plus 40db for 11th order products or greater.   The requirements for the 3rd to eleventh  order was  very modest  36db below PEP  for the 3rd and 5th order products. The 7th and 9th order products had to be suppressed by -35 below average power or 41db below PEP.

We typically find ham band transceivers whose IMD products  regularly sit on a plateau from the 3rd order to the 9th order  largely being the same with  the 11th order and above being  not much below these figures. Is it a wonder that ham transmitters cause so much harmful splatter.

This old FCC Part 80 Standard would be a good standard to  aspire towards if ever IMD regulations become mandated. There  must be a copy hiding somewhere on the internet. I have a copy somewhere on my old PC.  

We should set the IMD figure on the ERP power rather than the amplifier power, assuming a 10db gain antenna system and a 2500 PEP output it would  be reasonable to have a mandated IMD suppression level  suitable for a 25KW PEP commercial SSB transmitter.

You can see reasonable levels of IMD performance like this on transmitters from Selex and JRC that exceed -36db PEP for 3rd order with the critical high order products suppressed  very well for good engineering practice. These are 10kw transmitters not miserable 100 watt output radios! The JRC Ham radios also had excellent IMD performance that is unmatched to this very day. The JRC245 comes to mind.

We rarely use good engineering practice in Ham commercial  equipment design, its more about cheap and nasty engineering. JRC produce a JR900 10kw HF transmitter thats solid state that use pre-distortion that has  3rd IMD performance  of around -45 db or better.  Pre-distortion is our only hope in the ham service of achieving these kinds of excellent IMD numbers, we certainly cant achieve it with good engineering because the manufacturers are only interested in producing transceivers with rubbish performance  transmitters. How can it be good engineering when we see products reviewed in QST with -15db  below average for 3rd order IMD products? Thats as Class C CB dirty as it gets, totally disgusting garbage being sold to hams.



Title: RE: Ham Xcvrs' and Amps', Transmit Spectral Purity, IMD Products, vs. comm/maritime
Post by: W3RSW on April 17, 2018, 09:41:19 AM
Of course 10kW (10^5) is  10^3 times greater than 100 Watts (10^2) along with the concomitant 10^3 ratio of IM products.


Title: RE: Ham Xcvrs' and Amps', Transmit Spectral Purity, IMD Products, vs. comm/maritime
Post by: KA4WJA on April 17, 2018, 10:25:53 AM
Zenki, my man...
Welcome back!   And, thanks for helping return this discussion to the main point (that we, and the manufacturers can do better!)

This old FCC Part 80 Standard would be a good standard to  aspire towards if ever IMD regulations become mandated. There  must be a copy hiding somewhere on the internet. I have a copy somewhere on my old PC.

I'm pretty sure this is the old Part 80 mask....and as you can see it's pretty darn good....all transmit products beyond about 11.2khz away (2.8khz bandwidth x 4) from your transmit signal down -80db! and everything beyond +/- 5% of your freq, down -100db!  (I doubt anything can meet that spec today...but it's a nice goal!)

  (http://i61.tinypic.com/231pi1.png)



As for the JST-245....I think I mentioned it a while back??  But, if not, yep it's quite good for a 150-watt ham rig!
3rd/5th/7th/9th =  -39 / -56 / -57 / -60db(PEP)

Have a look...
(http://i66.tinypic.com/2r2lpph.png)



Along with a current production Icom (M-802), we can easily see that good IMD for HF rigs is not only possible but is actually being done every day by the same manufacturers that make some of our ham gear....and at 12vdc, no less!  :)
And, as I pointed out years ago, this doesn't add much to the cost of the radio....about $50 to $100, MAX!


Icom M-802's IMD (at 150 watts) =  -47 / -50 / -58 / -60db(PEP)  [and, note the roll-off of the higher-order products...]
(http://i67.tinypic.com/30u6cfd.jpg)



Zenki, thanks again!  (but, I still wish you'd ID yourself!)


73,

John,  KA4WJA


Title: RE: Ham Xcvrs' and Amps', Transmit Spectral Purity, IMD Products, vs. comm/maritime
Post by: KA4WJA on April 17, 2018, 10:48:24 AM
Rick,
If you're writing exponents, you're off by one order...

Of course 10kW (10^5) is  10^3 times greater than 100 Watts (10^2) along with the concomitant 10^3 ratio of IM products.

10kw is 100 times 100-watts....not 1000 times...
{btw, even though your math is off by a factor of 10, I haven't seen "concomitant" used in decades!  Good on 'ya!}

73,
John,  KA4WJA


Title: RE: Ham Xcvrs' and Amps', Transmit Spectral Purity, IMD Products, vs. comm/maritime
Post by: G0HZU on April 17, 2018, 04:49:43 PM
Quote
But, the point I'm trying to make is, there ARE currently full-featured, HF transceivers, that provide excellent service on the ham radio bands, that have excellent transmit spectral purity and extremely low IMD products, with the IMD products that actually cause most of the splatter (5th and higher order products), completely non-existent....
And, these radios are now currently on the market (and have been for years), at a reasonably "affordable" price...(< $2000)

Here's another possible 'typo' you made 4 years ago? Your old keyboard managed to suggest that there are sub $2000 radios out there that have 'completely non-existent' 5th order distortion terms :)

One solution would be to turn the transmit power down because then it would become more realistic to run a PA in class A. 10W PEP is only 10dB down on 100W PEP but a wideband class A PA at 10W PEP could have >=11th order IMD terms nearly 30dB better than the JST245 plot when measured wrt PEP. They will be even better in absolute terms because of the obvious difference between 150W and 10W PEP. So the interference level to other users could be about 40dB lower. But the class A PA will be expensive and will probably run at a steady 60W DC input power just to get 10W PEP. So it would need a decent heatsink and a fan.

Which radio PA is the ham going to buy if they both cost the same? The one that takes a steady 60W DC input power that only gives out 10W PEP or the one that runs at a similar average DC input power (with human speech) that can deliver 100W PEP?


Title: RE: Ham Xcvrs' and Amps', Transmit Spectral Purity, IMD Products, vs. comm/maritime
Post by: KM4AH on April 17, 2018, 07:08:11 PM
You can run Class A with a Yaesu FT1000MP Mark V which you can buy for $1100, or at least I did.


Title: RE: Ham Xcvrs' and Amps', Transmit Spectral Purity, IMD Products, vs. comm/maritime
Post by: KA4WJA on April 17, 2018, 07:27:16 PM
G0HZU (I would politely address you by your name, but you don't wish to provide that to us here, nor to qrz.com...and ofcom says you requested to not disclose...so...I cannot be as friendly as usual.)

So, sir, I'm taking you seriously....one last time... :)

Though, I wonder if you have read this whole thread??
Because it appears that you haven't??
If you have, I'd think you could easily have read enough of my ramblings (and facts) as well as much input from many others, that would certainly have clarified any "errors" or "outrageous" statements as typos...

I mean, seriously??
Can you not infer that what I meant (and thought I had written) was that most of the splatter was nonexistent....not that all IMD products were nonexistent.
I realize that we are separated by a common language, and I know that sometimes my mind is running at a different speed than both my fingers and my eyes (dyslexia)....but, I think if you take the time to read through things, the few odd typos will become apparent and easily understood...


Oh, and as for running a 100-watt rig at reduced power?  And/or Class A??
Yes, this has been discussed at length....

--- as you are aware, most find Class A operation of medium or high power PA's, to be a waste of power / produces heat-generation issues, etc. (yes, I know to you purists, there are ways to adapt to these issues, but at what cost?)...and if you care to read all the info here regarding the horrible ALC systems employed by the few production rigs with Class A PA's, you'd see that unless you operate without any ALC at all, there is little if any advantage in operating them in Class A...(the old MarkV did allow you to adjust the drive level and operate Class A without driving any ALC....and it's a nice rig...but long-since discontinued)

--- also, as can be easily seen, there is much more to this than just "turning the power down"....yes, many modern HF ham rigs will produce somewhat lower IMD products when operated at 60% to 75% of their rated power, some do not (and recent tests on youtube, of some newer rigs show fairly poor IMD when operated at QRP power, can't find the links at the moment, and they're not ARRL tests, but do show a frustrating result)....further my mentioning of the various PA designs / biasing / tuning that can provide lower higher-order IMD at the sacrifice of the lower-order products and vice-versa....but, even more on point here was the part of this discussion between Carl and I regarding the fine work done by Eimac, where their paper shows that drive levels (and varying biasing levels) / output levels can all be manipulated to produce PA's that "spec out" well, but fail to produce actual cleaner transmit spectra (another reason Carl, and others, hate two-tone testing)


HZU,  I hope you are seeing my point here...
You mention some obvious points, that all been fully discussed here, but have failed to grasp the gist of this thread:  That there are current production 150-watt / 12vdc PA, IF-DSP, HF transceivers, selling for less than $2000 USD, with fairly good transmit IMD....made by the same manufacturer that sells other HF rigs (our ham rigs), with inferior transmit IMD...


I scratch my head at times, wondering why some wish to find solutions (like running a PA in Class A, running QRP, only using SDR rigs with pre-distortion, etc.) that cost money, cost power output, cost heat, cost inefficiency, etc....when these same manufacturers already make reasonably priced radios that require none of these "solutions"??  :)
Just saying....your ideas are not bad ideas, but they've all been discussed at length, and fact is they aren't necessary to solve the problem....all that's needed is for hams to stop buying rigs with crappy transmitters and demand the manufacturers produce rigs with better transmit IMD!!
Problem solved!  :)



You ask the question of which rig the ham will buy??
Of course with just the two choices you give, if the ham doesn't understand the issues of transmit IMD, etc., he'll buy the 100-watt rig.
Which radio PA is the ham going to buy if they both cost the same? The one that takes a steady 60W DC input power that only gives out 10W PEP or the one that runs at a similar average DC input power (with human speech) that can deliver 100W PEP?
But, what if the ham had a choice to buy (for the same $$$) a 100-watt (or 150-watt) rig, with 10db to 20db better transmit IMD products??  (like an Icom rig, using the PA from a current-production Icom M-802)
I'd say, he'd buy this one...
But, if you're not informed that these radios, and these PA's, really exist....well then you're gonna' be stuck following expensive (in either money or transmit power, or both) trends like "Class A PA's", "running QRP", "SRD's with pre-distortion", etc...



Okay, enough for now....
HZU, I wish you well....but since I'm not really interested in going over all of this again, take care and 73.


John,  KA4WJA
 


Title: RE: Ham Xcvrs' and Amps', Transmit Spectral Purity, IMD Products, vs. comm/maritime
Post by: W3RSW on April 18, 2018, 08:01:14 AM
John,
4-2=2:  yer right , I got excited with the 5!

At any rate, a 10kW amp puts out serious signals along with somewhat serious IM products, even when properly down.  ;D



Title: RE: Ham Xcvrs' and Amps', Transmit Spectral Purity, IMD Products, vs. comm/maritime
Post by: G0HZU on April 18, 2018, 02:17:24 PM
Quote
HZU,  I hope you are seeing my point here...
You mention some obvious points, that all been fully discussed here, but have failed to grasp the gist of this thread:  That there are current production 150-watt / 12vdc PA, IF-DSP, HF transceivers, selling for less than $2000 USD, with fairly good transmit IMD....made by the same manufacturer that sells other HF rigs (our ham rigs), with inferior transmit IMD...
I'm not seeing your point at all... :)

All I see at the start of this thread are a few dodgy two tone plots and then a load of puffed up claims about marine radios.

I took the time to download the FCC test doc for your Icom 802 radio and I'm not impressed. The plots all look dodgy. The doc claims the plots are from an HP8564E analyser but they look to have been heavily processed.

However, the SSB plot taken at 2.182MHz at least shows the usual 100dB log display range of this analyser. Why didn't you post up this plot? It looks awful, it looks as bad as a dodgy export SSB CB radio from the 1980s. All the other plots have been cropped at an 80dB range and it looks like each plot was cropped and taken with max hold to hide all the crap.

A healthy 8564E analyser should have decent phase noise on a span like this but it looks like someone tried very hard to hide how bad this radio really is. The plots don't even look like HP8564E plots and look to be heavily edited. I can only assume it isn't really this bad and it was tested by a bunch of clowns. Maybe they didn't use an adequate PSU or maybe some RFI got into the system to generate all the extra crap in the spectrum.

Go on... post up the 2.182MHz SSB spectrum from this radio and let everyone see this radio in all its glory on a 100dB scale ;)


Title: RE: Ham Xcvrs' and Amps', Transmit Spectral Purity, IMD Products, vs. comm/maritime
Post by: KB2TIS on April 18, 2018, 03:26:16 PM
I took the time to download the FCC test doc for your Icom 802 radio and I'm not impressed. The plots all look dodgy. The doc claims the plots are from an HP8564E analyser but they look to have been heavily processed.

What, you think the asymmetrically drawn mask and data that isn't centered in the mask might be suspect?


Title: RE: Ham Xcvrs' and Amps', Transmit Spectral Purity, IMD Products, vs. comm/maritime
Post by: G0HZU on April 18, 2018, 04:00:59 PM
I'm just making the observation that the plots look to have been heavily processed by someone and this is quite odd. Some are cropped to 80dB and they don't look like raw plots from this series of analyser anymore. Even the text around the scaling looks unconventional. I can understand the need to add a mask line to the plot but why not do this to a raw 100dB plot from the analyser?

https://fccid.io/AFJIC-M802/Test-Report/test-report-233420

Also, if you look at plot 5-2 in the link above and then compare this 100dB plot to the K3 100dB plot in the first post on this thread, then they both look to be really poor. It looks like some 2nd order distortion is present in the Icom 802 plots and sometimes this can happen with RF getting back into the radio. Or it could be that the radio is being driven very hard at the mic input with the AF test tones. I'm not sure if a PSU problem could cause this but the radio will be munching current from the PSU at the difference frequency of the test tones.

Either way, the Marine radio looks to be nothing special in this plot. I'm assuming that the extra tone inside the AF bandwidth is a distortion term rather than some sort of pilot tone. It looks like 2nd order distortion to me (that then appears as extra IMD across the whole plot) but maybe someone else can comment.

The 80dB plots all look to be using something like MAX HOLD across multiple sweeps. Maybe this is a requirement in the test but it does serve to make the IMD terms look more like innocent noise in the analyser. Cropping the 100dB capability of the analyser to 80dB seems an odd thing to do but it also gives the illusion of good performance at a casual glance, especially if the form factor of the plot is stretched to that of the 100dB plot.


Title: RE: Ham Xcvrs' and Amps', Transmit Spectral Purity, IMD Products, vs. comm/maritime
Post by: G0HZU on April 18, 2018, 06:24:44 PM
Quite a few of the SSB plots across 1.6-28MHz look fairly average and they all seem to have the extra distortion terms and plenty of mush between the major distortion terms. I'm not sure if this mush comes from a poor setup or if the radio has issues with ALC stability at certain drive levels. Or maybe it's being driven really hard at the mic input so the ALC is struggling? Otherwise I can't explain why the plots look so mushy on an analyser as good (as in having low close to carrier phase noise) as an HP8564E at these test frequencies. Assuming the analyser is OK then all of the noisy mush must come from the radio or the rest of the test setup and it looks to be spread out to quite a few kHz. Sometimes you can see mushy pickup effects on a two tone test if an AF test cable isn't screened very well. Otherwise it might eventually look like noise if you left it on MAX HOLD when set to the positive peak detector for a certain number of spans I guess?

It doesn't look right to me. When I first saw the plots at the start of the thread showing an 80dB log range I assumed some old noisy dog from the HP859x spectrum analyser series was being used. So the 'noise' didn't look suspicious.




Title: RE: Ham Xcvrs' and Amps', Transmit Spectral Purity, IMD Products, vs. comm/maritime
Post by: KA4WJA on April 25, 2018, 10:51:46 AM
Okay, I hadn't planned on being back here, at least not so soon, but I see that G0HZU has posted something very helpful!  So, thank you for the link to the report...I didn't have that.  :)  
(as everyone that has read all of this thread knows, as I wrote right here, years ago, I got the scans from some friends at an EMC/RF compliance lab, who got 'em from the FCC test report....and they only gave me two scans, and only one of which I actually had in this laptop.)

Because of this helpful info, I'm trying to believe that you, G0HZU is just trying to be helpful, but the tone of your writing is rather accusatory??  You accept my word and apology on my typos and have sent the link to the test report, (and hopefully accept my thanks for that), but why the harsh tone??  
Aren't we all hams, just trying to learn and help others, and each other??  Please sir, (my name is John, but you haven't given your name) as your tone is rather harsh and accusatory, would you accept a tiny bit of advice?...I think if you just smiled a little and were less abrupt in your words, you would be better welcomed among your friends and fellow hams...if not, no worries here, as I take no offense, but I'm not likely to take you on your word. :(

Also, please remember, I did not do these tests, I am not selling radios of any kind (maritime or otherwise), and am not in the RF design/engineering business....(yes, I have made my living in communications, but these days mostly consulting)...I have not recommended buying/using marine HF radios for hams, etc....I'm just a long-time ham who has found a world of difference (on-air) between the transmit IMD of "adjacent channel" operations on HF (3khz to 10khz away), between ham transceivers and maritime transceivers, over many years....and things have gotten worse (and lately, with the "all knobs to max" crowd on HF, things have gotten a  lot worse!)....and a few years back, when mentioning this to some of my fellow ham buddies, a couple of them sent me these scans of the M-802...and this is why I started this thread!   I have given as much factual info that I had, and included my actual on-air experiences as well.. So, if you have something helpful to add, please do so....but, if would please leave the accusatory attitude on your side of the Atlantic, most of us would appreciate it. :) Thanks!

{If you actually read this thread, you would already understand all the above. :) }


Secondly, until you mentioned the difference I never placed much emphasis in the older scans from Rob Sherwood, NC0B, showing 100db on the screen, versus the ARRL tests (and the FCC test reports) showing 80db on the screen....so I'm reposting a couple images cropped to show 80db, just for ease of comparison.  (the only "100db" scan of the M-802 that I see was that one on 2182)

Here's the K3 (on 20m, I think), showing just to -80db(PEP):

(http://i63.tinypic.com/vyv6lj.png)


Here is the M-802 (on 16mhz), showing to -80db(PEP):

(http://i64.tinypic.com/2lue904.png)


Here is the Collins 32S-3, showing to -80db(PEP):

(http://i66.tinypic.com/64qa6d.png)


Here is the Icom IC-781, showing to -80db(PEP):

(http://i67.tinypic.com/2wm456r.png)


Here is the Yaesu FT-1000 MkV (in Class A, with no ALC), down to -80db(PEP):

(http://i66.tinypic.com/anbztv.png)


Here is the JRC JST-245:

(http://i64.tinypic.com/5ez52c.png)

Hope this helps some.  :)



Third, as I've stated many times in this thread, while I do own two M-802's and use one often (and I do like it, but nearly as much as I like my ~ 40 year old TR-7's!!), I was not specifically praising the M-802, nor again, was I advocating all hams use HF Maritime transceivers, but rather I was just using it as an example of HF rigs that have better transmit IMD than our crop of HF ham rigs of the last 20 - 30 years!  And, I firmly stand by my words, and my desires, (excepting typos, or when new/different  info is given) for better transmit IMD from our "modern" ham rigs!  :)  
[And, in my opinion, I feel running off on a tangent about an anomaly of one radio, on 2182, etc. is rather disingenuous if your intention is to help, but that's just my opinion of course.]



Fourth.... now that I have the whole report (again, thanks to G0HZU) I also see an odd 2182khz scan....since there was a 2182 requirement for an "AM Equivalent" (H3E) signal / DSB-reduced-carrier / DSB with carrier, perhaps this was a mis-tuning of the PA, or an anomaly of the radio, or as you wrote, an overdrive of the mic audio in?? (but, since it still met the FCC spec, no worries??)  The J2B test on 2182 is better, but also rather poor.  So, on 2mhz...the M-802 isn't all that great...(but since all the scans from ARRL tests and from Rob, NC0B, were for 20m, I was using 16mhz tests of the M-802....thought it was 12mhz, but turns out it was 16mhz...and there is no denying that the M-802 is better than most/all of our modern HF ham rigs...)

FYI, as for the "mush", etc....I personally know that the early M-802's suffered from an erratic clipping issue in the APC circuit, which manifest itself on different bands/freqs (not everywhere)....the fix came in 2006 or so (after 3 yrs of production) and Icom still offers this fix (a hardware change on the APC board) for free, for all M-802 owners as a "no-charge, out-of-warranty service", and at the same time, they test/align radio to factory specs, all for free....(I had one of my M-802 so "updated" by Icom...the other is newer and was manufactured after the factory fix)

And, I suspect that this "mush" and some of the other anomalous products in some of the scans to be examples of this original issue...of course, I cannot be certain (and it just might be a poor test set-up/over-drive), but knowing about this issue and now seeing the spectral scans, it does make sense...{BTW, it did take Icom almost two years of field complaints until they stepped-up and found the problem....but once they admitted it (about 2006), they stepped-up very well and even today, continue to honor a "no-charge, out-of-warranty" repair to all M-802 owners, worldwide}



Whew, I'm tired!  :)
Finally, to be clear here, to me, the images in the report do not appear to be cropped at all....yes, all but the one you mention, are done only down to -80db, but they don't look cropped, and while the "mask" might not line-up the way you like, this is getting weird, being so overly critical of someone stranger's work, and not giving them the opportunity to reply here (call him and ask him what was up with the things you don't like, why post quasi-anonymously in a public forum??)
So, with that, G0HZU, you win...
I'm not going to argue with you about images on a test report from ~ 16 years ago, done by someone that neither of us knows....that is just rude, and I will not continue to feed this part of the discussion....
So, you win....and when I write "73", I do mean it.  :)


73,

John,  KA4WJA


Title: RE: Ham Xcvrs' and Amps', Transmit Spectral Purity, IMD Products, vs. comm/maritime
Post by: KM1H on April 25, 2018, 11:54:55 AM
Quote
So, with that, G0HZU, you win...
I'm not going to argue with you about images on a test report from ~ 16 years ago, done by someone that neither of us knows....that is just rude, and I will not continue to feed this part of the discussion....
So, you win....and when I write "73", I do mean it.

Are you finally thru?


Title: RE: Ham Xcvrs' and Amps', Transmit Spectral Purity, IMD Products, vs. comm/maritime
Post by: G0HZU on April 25, 2018, 03:16:41 PM
I hope it's over...  :)

Quote
But, even more impressive is the fact (sorry I don't have the scans to "prove" it) that a couple older "12 volt" HF marine transceivers, have even BETTER transmit spectral purity and even lower transmit IMD products....
Such as the Icom M-700Pro (which is a 1990's design, that just ceased production about 7 - 8  years ago, and retailed for ~ $1250...and can be purchased used nowadays for about $500 - $700) had even lower phase noise, and all IMD products down better than 75db...and here again, this is at 150 watts PEP output continuous-duty (FSK/SSB/CW)..
Yes it did have a full vfo as well as 150 channels, etc....but not too many "ham-radio-type features".....but its "12 volt PA" and its entire transmitter was VERY clean...(actually better than a Yaesu FT-1000 in Class A)

My guess this crazy claim was based in a misinterpretation of the -75dB spurious spec on the Icom datasheet for the M700pro. I looked up the schematic for the 700pro and the three stage PA looks to be very similar to the 12.5V class AB PA in the Icom 735 mobile 100W ham radio from the mid/late 1980s. Same predriver, same drivers and same PA devices. The transformer ratios will probably be different to permit the 700pro to run to 150W PEP but otherwise they look quite similar to me.

In the real world, a 3 stage PA like this will generate distortion in each stage and there could be IMD phase cancellation effects at certain drive levels and certain transmitter frequencies and tone spacings. Also, even with a perfect 50R dummy load the PA transistors will not see a consistent resistive load because of the suite of LPFs and the n:1 transformer between the PA transistors and the 50R load. So this is another factor that can cause IMD sweetspot effects at certain frequencies and drive levels. So a transmitter can look OK on one band but not so good on another.  I think it's possible to optimise the driver and PA bias levels for best IMD close in or far out and the other degree of freedom is what load the output n:1 transformer presents to the PA when you want it to produce (say) 100W PEP. It should be possible to optimise this such that close in IM terms go down in a sweetspot... so many ways to fiddle the 2 tone plots! But overall it's hard to escape the real world limitations of a class B/AB PA running at 12.5V. That's why I said earlier that the only person that gets the full information from two tone testing is the person who does the testing and a lot of information is lost once a single plot is produced at the favoured (or unfavoured) drive level or tone spacing.


Title: RE: Ham Xcvrs' and Amps', Transmit Spectral Purity, IMD Products, vs. comm/maritime
Post by: VR2AX on April 26, 2018, 03:55:40 AM
Possible proof reading error.


Title: RE: Ham Xcvrs' and Amps', Transmit Spectral Purity, IMD Products, vs. comm/maritime
Post by: KA4WJA on April 26, 2018, 01:15:24 PM
Carl, you're cool!  I really mean that!  :)  
It took me a while to realize it, but you're a good guy!

Me, done??  Nah, not likely... :)
Although, I don't have that much time these days....I'm not done.  :)
I'll check back if needed from time to time..
(just done arguing across the pond)

73,
John,  KA4WJA

~~~

HZU, not sure if you're having trouble reading or it is a memory issue, but I'm sorry.
If you look a couple weeks ago, we already dispensed with the fact that I made a typo / proof-reading error.  Sorry, I don't have the time to go over everything again, sir....but..

But, here is what I wrote....and gee, even Carl realized this error from 4 years ago was a typing error / proof-reading error, I mean not even Zenki would post hogwash about all IMD being down better than 75db.   (and, know I did not reference a "spurious emissions spec"...  Really??

Okay, guys....thanks for pointing out a typo of mine that I made almost 4 years ago.. :)
Until this afternoon, almost 4 years hence, I did not realize I had made this typo / error!!

What I thought I wrote in regards the old M-700Pro, was that "all higher-order IMD products down better then 75db" (meaning products higher than the 9th order...such as 11th, 13th, 15th, etc...)
Sorry, about the "typo" / "omission" of that critical point!!  :(
{BTW, how come nobody else caught this???  'cuz, even Zenki would cry BS on a IMD3 of -75db!!  :) And, certainly anyone that reads this whole thread could see that this must have been a typo / error!!}

But, even more impressive is the fact (sorry I don't have the scans to "prove" it) that a couple older "12 volt" HF marine transceivers, have even BETTER transmit spectral purity and even lower transmit IMD products....
Such as the Icom M-700Pro (which is a 1990's design, that just ceased production about 7 - 8  years ago, and retailed for ~ $1250...and can be purchased used nowadays for about $500 - $700) had even lower phase noise, and all IMD products down better than 75db...and here again, this is at 150 watts PEP output continuous-duty (FSK/SSB/CW)..

To be honest, I read / proof-read the posting....but when you just got done writing something, sometimes what is in your head is what you think you just read!  
Opps...
Sorry about this!

Now, HZU, I am glad you posted a link to the test report and I hope the clarifications I made to you help.


73,

John,  KA4WJA


Title: RE: Ham Xcvrs' and Amps', Transmit Spectral Purity, IMD Products, vs. comm/maritime
Post by: G0HZU on April 26, 2018, 04:13:22 PM
KA4WJA, I'm just trying to do a technical analysis of your unrealstic claims in your first post. The first post sets the topic of discussion for the whole thread. Each time I reply I try and keep my posts relevant to the technical issues. But each time you reply to me you patronisingly question my integrity and this time you've questioned my memory and my literacy. You've also used words like 'rude' and 'disingenuous' to describe my technical input.


Quote
What I thought I wrote in regards the old M-700Pro, was that "all higher-order IMD products down better then 75db" (meaning products higher than the 9th order...such as 11th, 13th, 15th,
etc...)
Yes, you previously clarified that you made a typo. However, that clarification makes your subsequent claim (made in the same paragraph) against the Yaesu FT1000 look even more unrealistic and that's why I quoted it again and here's the last bit of the quote if it helps...

Quote
KA4WJA: but its "12 volt PA" and its entire transmitter was VERY clean...(actually better than a Yaesu FT-1000 in Class A)


That's why I quoted this in my previous post! I offered in my previous post that this 'better than a Yaesu FT-1000 in Class A' claim was possibly based on the overall -75dB spurious spec in the Icom M700pro datasheet. But you now seem to have ruled this out in your latest post. So, armed with this and your typo clarification, you must think that the Yaesu FT1000 in class A will produce worse 9th to 15th order IMD than a 12.5V class AB PA in an ICOM M700pro radio? Otherwise, what else am I left to conclude? Was this just another elaborate typo of yours? The M700pro PA looks to be very similar to the class AB PA in the Icom IC735 mobile 12.5V ham radio and I suspect that its IMD performance will be fairly typical of this type of radio and nowhere near the quality of a proper class A PA.

You also claimed in your first post (quoted below) that the IC802 IMD plots were similar to a Yaesu FT1000 in class A

(http://i43.tinypic.com/2iqeiro.jpg)

(http://i43.tinypic.com/15mxyyp.jpg)

Quote
KA4WJA: (these are about what the old Yaesu FT-1000 did in Class A....)

Was this another typo or are you claiming that the M802 is about the same as a Yaesu FT1000 in class A? If so, the Yaesu FT1000 vs M802 plots on this thread all seem to be proving you wrong by a
huge margin... The M802 IMD plots look to be mushy with plenty of spurious terms but the Yaesu FT1000 in class A looks to be much cleaner and this should be no surprise!


Title: RE: Ham Xcvrs' and Amps', Transmit Spectral Purity, IMD Products, vs. comm/maritime
Post by: K6AER on April 28, 2018, 01:05:48 PM
This post is like reading War and Peace. On a typical day, on 40 meters, would any one notice a IMD of 30-35 dB (third order) as compared to one with an IMD of 40 dB. All this on a band of over modulated signals, typical thunder storms and hams calling CQ 2 KHz from a QSO and every wall charger on the planet making the noise floor climb.

This never-ending post seems to be a poor excuse for not getting on the air and communicating the old fashion way.

I went out to the QRZ site for KA4WJA and his station is mostly 70’s equipment that would be lucky to have an IMD better than -30 dB.  This whole IMD quest is a tempest in a tea pot.

I was wondering if their is a E-Ham award for works all E-Ham states in a post?


Title: RE: Ham Xcvrs' and Amps', Transmit Spectral Purity, IMD Products, vs. comm/maritime
Post by: K3LI on April 28, 2018, 01:20:49 PM
Agree.  I challenge anyone to prove they can actually hear the difference.  Not measure, hear.  Nope you wont.  Much posting about something that doesn't matter squat.

I have had QSOs with folks during which we discussed antennas.  After a discription of the antenna I was using, he proceeded to tell me that it was wrong and I should do this, that, and
the other.   I ask the guy:

1. How is my signal again?
    5-9 plus a lot

2. How is my voice?
    Outstanding.

3.  So my voice is great and my signal is booming?
    yes.

Tell me again what I'm doing wrong?

The point is, if something works, it works.   All the mumbo-jumbo in the world does not matter.   If you hear me fine, and I hear you fine, all is good.   
Never had a dipole higher than 30 feet.  Talked all over the world with my dipole.   Hex beam at 28 feet works like a champ.


Title: RE: Ham Xcvrs' and Amps', Transmit Spectral Purity, IMD Products, vs. comm/maritime
Post by: KM1H on April 28, 2018, 04:22:14 PM
Quote
Agree.  I challenge anyone to prove they can actually hear the difference.  Not measure, hear.  Nope you wont.  Much posting about something that doesn't matter squat.

That is very easy to prove and I challenge you to understand how & why


Title: RE: Ham Xcvrs' and Amps', Transmit Spectral Purity, IMD Products, vs. comm/maritime
Post by: K9RJ on April 28, 2018, 10:57:06 PM
http://audiosystemsgroup.com/TXNoise.pdf


Title: RE: Ham Xcvrs' and Amps', Transmit Spectral Purity, IMD Products, vs. comm/maritime
Post by: KM1H on April 29, 2018, 08:37:03 AM
That article should be required reading by all and several times for the less technical in helping them make choices about some current as well as used products.

Is Jim planning on regular updates?

Carl


Title: RE: Ham Xcvrs' and Amps', Transmit Spectral Purity, IMD Products, vs. comm/maritime
Post by: VK3BL on April 29, 2018, 08:48:48 AM
Find me a single example of a 12V Ham transceiver where 5th order products (2 tone) DONT dominate at full rated output....

The reality of white noise or SSB voice is different, however.


Title: RE: Ham Xcvrs' and Amps', Transmit Spectral Purity, IMD Products, vs. comm/maritime
Post by: KA4WJA on June 07, 2018, 06:36:28 AM
Just some thank you's and very brief clarifications.  :)  (no, I'm not rehashing anything!)

I do appreciate the fine comments and helpful info that some have provided here.  And, once again, allow me to say how much I respect the expertise and experience of guys like Carl and Mike...(even if we do sometimes disagree).  
I sent Carl and Mike some friendly thanks, directly via e-mail...but unable to do so to HZU, so thanks to him as well, for holding our feet to the fire, and accept my apologies if I ever seemed rude (not my intent)...

While some of us have gone 'round-n-'round on some minor issues (and yes, unfortunately I contributed to some of that fairly useless merry-go-round, too)...
I realized that the main point and original impetus of this discussion may have gotten lost.  :(

So, just for clarification and to sum up:

1)  I personally experience rather poor transmit IMD from (barefoot) ham radio HF transceivers used illegally on the maritime bands (and have seen this for many years now)....30 to 40 years ago, when it was mainly HF maritime rigs and a few Atlas 210x's, Icom 761's, and Drake TR-7's, this wasn't a major issue....but over the past dozen years, it has gotten a lot worse.  (and, for clarity sake, yes I can hear the difference / the splatter is worse....some of the new ham rigs have 10-20db worse IMD products infringing on both adjacent channels and users well down the band / 10khz+ away...)

2)  And, you combine that with my personal experience of seeing/hearing more of the HF ham phone bands with some fairly crappy signals, with poor transmit IMD (gotten worse over the past 10 - 15 years)....compared to what I remember from decades ago! {I have some found memories of the old days, with many "Kalifornia Kilowatts" on-the-air....memories from mid-70's, of studying for my license, listening to clean signals on 75m (when I should've been copying CW in the Novice sub-band)....back then, except for a raucous DX pile-up, even 20m wasn't too bad....But, I digress!}  
In my own personal experience, things have taken a turn for the worse lately (last 10 - 15 years) in regards to my fellow hams HF signals and their poor transmit IMD...(and, again for clarity sake, yes I can hear the difference....except for a quiet weekday, I hear quite a bit of splatter on-the-air these days...)

3)  And, then look at what some of our popular / high-scoring contesters and DX-er's have been saying for the past 10+ years...
Paraphrasing them: "the receivers are better than most hams can effectively use, as the transmit IMD and noisy transmitters are the limiting factor in our HF realm, these days!"  
(and please remember that those are the same guys who were complaining about our poor receivers a decade or two earlier....and their demands of better receive performance is why we have the excellent receivers that we have today!!)


Now, you combine those three things together with the transmit IMD test results of modern HF rigs (both ham and maritime), some of which I had access to a lot of data, some not so much...
And, viola....you have the reasons I started this thread in the first place!

Now, yes....there were some of the oft read frustrations like:
"the tests weren't done right",
"I don't see why some scans are different",
"why are some displayed 'wrong' ",
"where did this come from",
"who are you to tell me this", etc....
....along with the usual ARRL bashing, etc.
And, yep, I get it....these can be valid points....
And yes, I tried to defend 'em, but I just don't have the time / inclination to do much more... :)  (you're welcome)


So, the main point here, today, is:

These are the honest, real-world, experiences I've had over the past decades...
And test results that I had available (from ARRL, from Rob, NC0B, from a few friends at EMC test lab, etc.)....
And while, yes over-driving an amp could account for some of the crappy signals on the HF ham bands, none of my experiences on the HF maritime bands had any amps at all...
And further, that while I agree with Mike that those with their mic gain, etc., cranked-up are the cause of some (a good deal?) of the horrible splatter we hear, the undeniable fact is that most of our "modern, 21st Century" HF ham rigs have fairly poor transmit IMD, even when operated in their prescribed manner / with good engineering practice, with the mic gain properly set!  
(and btw, my comments regarding the FT-1000 in Class A, as well as the FT-5000 in Class A, were regarding the fact that if you had any ALC at all, the actual result was only marginally better then if you ran the rig in Class B, and certainly not that a maritime rig was "better" than a Class A PA, just that the way Yaesu uses ALC makes the use of Class A fairly moot, if you have any ALC....sorry, if I didn't spell that out clear enough...)

And, that my friends and fellow hams, is/was my primary gist/goal of this discussion....that's it....
Look at the specs (and spectral scans)....we've been through all the ancillary arguments, and I don't think much more can be done further discussing them....so, if you disagree with me, no worries, I take no offense, but please just try to understand that the only agenda I had/have is to bring some info to light, spurred-on by own, real-world, on-air, experience and my research....  :)  
{and, just to reiterate, I never wrote that hams need to use maritime rigs, nor that everyone needs to scrap modern technology and go back to a Collins 32S-3....just that we can do better than what we're "being sold" these days....and it's up to us to demand better, by spending our dollars/euros only on rigs with better transmit IMD, as well as educating ourselves and fellow hams of the issues (including keeping the mic gain at the proper level!)...}


Finally, Mike...I will repeat again, I respect your expertise in RF engineering (and have learned from you), and I agree that the mic gain is a problem....but...

(I'm hesitant to write this)...But, perhaps I wasn't clear in that I operate HF these days mainly from my boat (or other location) with my Icom M-802's, barefoot....I got a feeling that you were implying that somehow I'm not "legit", because I have some old equipment at home (Drake TR-7's and Alpha 77SX, for HF....homebrew 144mhz transverter and Henry 2002, for EME, etc...but some tower / antenna damage and lost trees/wire antennas from storms/hurricanes, means that even when I am home I don't operate from there), and haven't added/updated my qrz.com profile in a long while (~ 12 - 15 years?)...
I do hope that I an wrong in this perception??  
As, I really hope that ham radio can be both a service (Amateur Radio Service) and a nice hobby....AND, a great place to learn from each other, etc., without falling into the traps of our modern society, like Facebook/Instagram, etc...
{Oh, and fyi, while it's not as good as some commercial maritime rigs, in my notes joted down in my owner's manual, many years ago I measured my original TR-7 (at 100 watts PEP out?) 3rd order at -38db(PEP) and 5th order at -44db(PEP).....and while I don't have it written down, I believe 7th and 9th were in the mid-50's....these are a fair bit better than some of the more "modern" rigs...but, this was > 30 years ago, and while I have cleaned / aligned the rig over the years, I admit I haven't 2-tone tested in decades, but also haven't used it in years, either. :( }


Okay, that's all I got for now....hope some here have gotten something out of this.  :)


Fair winds.

73,

John,  KA4WJA


Title: RE: Ham Xcvrs' and Amps', Transmit Spectral Purity, IMD Products, vs. comm/maritime
Post by: W9IQ on June 07, 2018, 08:34:28 AM
It seems that throughout this thread, the implied smoking gun of IMD is the tranceiver's output amplification stage. Has anyone quantified the IMD effects of the multiple up stream AF/RF amplification/mixer/filter stages? While these may be more nearly linear by design, I would assume they have a measurable, if not dominant, effect.

- Glenn W9IQ


Title: RE: Ham Xcvrs' and Amps', Transmit Spectral Purity, IMD Products, vs. comm/maritime
Post by: KA4WJA on June 07, 2018, 09:12:52 AM
Glenn,
You're correct here....this is mostly about the transceiver's PA...
It seems that throughout this thread, the implied smoking gun of IMD is the tranceiver's output amplification stage.

Except for mis-adjusted mic gain, and/or overdriving of amps, etc...For SSB operation, etc., it's mostly (all?) about the PA stages....
Although anything (including filters) can be non-linear, and contribute to transmit spectral issues (IMD, etc.), to the best of my knowledge, the IF's, filters, and last mixer (1st mixer) contribute little, if anything, to the transmit IMD issues of our modern HF ham rigs...and the rigs' oscillators' noise contributions are a very small factor to the rigs' transmit spectral purity in SSB operations...(but, I could be wrong??)
{although, in CW operation the transmit noise (oscillator phase noise) does play a significant part in th rig's transmit spectra....although in most cases the hard-keying (short rise and fall times, of less than 4 to 5ms) plays the major role...see reference to K9YC's article, regarding this..}
But...


But, I actually don't have an absolute answer for you... :(
Has anyone quantified the IMD effects of the multiple up stream RF amplification/mixer/filter stages? While these may be more nearly linear by design, I would assume they have a measurable effect.

- Glenn W9IQ
To be honest, I've never looked at my low-level (0dbm) output of my rigs, directly....

But, I did look at my spectral purity of my 144mhz transverter (which uses a 0dbm output of my TR-7, on 28mhz), and found no issues....(but, honestly that was 30 some years ago, and I don't remember what I found...except for a frustration with a "spur" that developed from my transverter's 144mhz PA....turned out that the VMP-4 that was supposed to be good for 7+w, was producing a spur of about -30dbc a few mhz away, when output was > 4 watts....but, disappeared altogether at outputs <3 watts...luckily all I needed was 2 watts, so I was golden! :) )


So, I cannot say that I have any real-world quantitative data for you.  :(
But, Carl and/or Jarrad might???
Perhaps they will chime in...

Since there is no reason to assume that the output of the mixer (at ~ 0dbm) that goes to the pre-driver, driver, and final PA of our rigs, is non-linear....I (like everyone else) assumes there is little contribution from them to transmit IMD...


But of course, for CW operations, the transmit noise (oscillator phase noise) is a significant contributor to the rig's transmit spectra....although, in many cases the hard CW keying (rise times < 4ms to 5ms) is the major component of the rig's transmit bandwidth and close-in spectra...


Glenn, I hope to learn from your question....

73,
John,  KA4WJA
 

 
 





Title: RE: Ham Xcvrs' and Amps', Transmit Spectral Purity, IMD Products, vs. comm/maritime
Post by: KM1H on June 07, 2018, 09:35:28 AM
It seems that throughout this thread, the implied smoking gun of IMD is the tranceiver's output amplification stage. Has anyone quantified the IMD effects of the multiple up stream AF/RF amplification/mixer/filter stages? While these may be more nearly linear by design, I would assume they have a measurable, if not dominant, effect.

- Glenn W9IQ

With the low level audio and RF amp stages being Class A, modern filters and mixers being far better than even 20 years ago, their IMD contribution does not fall into the GIGO category of yesteryear.

Even so the mid 80's TS-830 is capable of a real IMD in the low -40's; I dont know about the other KW hybrids.

Carl


Title: RE: Ham Xcvrs' and Amps', Transmit Spectral Purity, IMD Products, vs. comm/maritime
Post by: K6AER on June 13, 2018, 04:48:38 PM
KA4WJA,

You have posted on this thread 59 times. Do you ever get on the air?

Mike


Title: RE: Ham Xcvrs' and Amps', Transmit Spectral Purity, IMD Products, vs. comm/maritime
Post by: KA4WJA on June 14, 2018, 02:47:26 AM
Mike,
Yes, I do get on the air, but in case you missed it, not nearly as often as I used to, nor as often as I'd like to!
I do have much more pressing priorities, such as some family matters (that I'd rather not discuss publicly, if that's okay), and sometimes find that I have a few minutes to spare when I can get on-line (such as doctor's offices, or late at night but cannot disturb anyone, etc.)....and I'm not online much....

BTW, you did get my personal e-mails of respect and explanation, but instead of politely accepting, you choose to show a rather harsh outlook on your fellow man here, instead of understanding that we all are individuals and have different priorities??

In the world I live in, we can all be different, have different opinions and share them with each other and still respect each other....perhaps you do not live this same philosophy??  But, I do still wish you well.

Finally, you have more than 5 times the number of posts than I do, over the same number of years.
What does that have to do with anything?

73,
John,  KA4WJA



Title: RE: Ham Xcvrs' and Amps', Transmit Spectral Purity, IMD Products, vs. comm/maritime
Post by: K6AER on June 14, 2018, 10:58:26 AM
My postings are on all subjects. I don't have my panties all in a wad over IMD which I cannot control any more than bad behavior on 80 meters.

I have been posting on E-Ham since they started. 60 postings on one thread would indicate you like to keep the thread alive at all cost.

Through all of the verbiage on IMD I have not any evidence that having an station IMD number better than -35 dB would improve the band operating with our current band noise floor of -108 dBm. With summer lightning that number drops to -90 dBm.

I noticed on QRZ.com your main radio is a TR-7. These radios have never had better than -30/-34 dB IMD on their  3rd and 5th IMD two tone numbers at 100 watts out. If IMD is your main concern why not a better radio?

This IMD thread is nothing more than a tempest in a tea pot.



Title: RE: Ham Xcvrs' and Amps', Transmit Spectral Purity, IMD Products, vs. comm/maritime
Post by: VA7OJ on June 14, 2018, 11:20:38 PM
Find me a single example of a 12V Ham transceiver where 5th order products (2 tone) DONT dominate at full rated output....

The reality of white noise or SSB voice is different, however.

Hi Jarrad,

Here is an example of a radio I tested in which TX IMD5 < IMD3.

http://www.ab4oj.com/icom/ic7600/7600notes.pdf (http://www.ab4oj.com/icom/ic7600/7600notes.pdf)  p. 21

All this fuss about IMD performance of amateur transceivers overlooks the fact that the ITU-R guideline (SM.326-7 §1.2.3) specifies -25 dBc for single-channel J3E, and -35 dBc for B8E (ISB). This is quite modest. I do not think an OEM will 'bust its hump' trying to exceed this guideline unless the radio set is type-approved for radio services requiring a tighter transmit IMD spec.

73, Adam VA7OJ/AB4OJ


Title: RE: Ham Xcvrs' and Amps', Transmit Spectral Purity, IMD Products, vs. comm/maritime
Post by: HAMHOCK75 on June 15, 2018, 02:20:41 AM
Here are what some of these products look like on a public access SDR. Notice in the image below that there is a station occupying more than three times the spectrum of other stations. Listening to the LSB as shown sounds fine.

(http://www.mediationdangers.com/stuff/wp-content/uploads/2017/07/IMD.jpg)

There is nothing heard listening below the LSB until that station comes on, then there is what sounds like garbled audio.

(http://www.mediationdangers.com/stuff/wp-content/uploads/2017/07/IMD5.jpg)


Title: RE: Ham Xcvrs' and Amps', Transmit Spectral Purity, IMD Products, vs. comm/maritime
Post by: KM1H on June 15, 2018, 06:13:25 PM
Quote
http://www.ab4oj.com/icom/ic7600/7600notes.pdf  p. 21

All this fuss about IMD performance of amateur transceivers overlooks the fact that the ITU-R guideline (SM.326-7 §1.2.3) specifies -25 dBc for single-channel J3E, and -35 dBc for B8E (ISB). This is quite modest. I do not think an OEM will 'bust its hump' trying to exceed this guideline unless the radio set is type-approved for radio services requiring a tighter transmit IMD spec.

73, Adam VA7OJ/AB4OJ

Even using the ARRL PEP method the 3rd sucks and the 5th isnt much better. Sweep tubes could do better in the 60's.

What is the reference point of the ITU spec?  BTW the commercial SSB is channelized so close in IMD isnt a problem plus there is no mike gain control, no audio processor, and no access to the internals for Hammy Hambone to get his dick skinners into.

Carl


Title: RE: Ham Xcvrs' and Amps', Transmit Spectral Purity, IMD Products, vs. comm/maritime
Post by: K6BRN on June 15, 2018, 07:21:36 PM
Carl:

Tube finals could do better for many reasons (see below), but what they were better at was not quite as desireable as what a solid-state amp provides in return...

1.  The simple analog oscillators of the day had phase noise that was determined largely by the quality of their crystals, not the jitter of their DDS/NCOs as in modern radios.

2.  The RF final amps in radios and external "linear" amps were as dirty as heck (usually push-push architecture with just over 180 degrees of conduction angle), but they had the major advantage of a tuned, narrowband relatively high Q filter (tank circuit) right after them, vs. a broadband amplifier with "no-tune" broadband filters on the output.

No reason that a similar tunable, resonating narrowband filter could not be attached to a solid state amp to improve performance.  With a lot of extra parts.  And significant loss of efficiency (lower voltage amps means much higher current in the tank - or a broadband transformer - ack!).  And the need to always take the time to "tune up" the amp.  So I guess the marketplace decided it could live with poorer IMD (some of the time - tube amp performance always depended on an operators skills in tuning/loading) to receive simpler operation and longer life in return.

I've still never heard what the immediate, obvious and critical value a 10 db reduction in IMD would yield for the user of, say an FTDX-3000.  Usually the reasons listed are pretty squishy.

Brian - K6BRN



Title: RE: Ham Xcvrs' and Amps', Transmit Spectral Purity, IMD Products, vs. comm/maritime
Post by: VA7OJ on June 15, 2018, 08:04:40 PM
What is the reference point of the ITU spec?

The ITU-R guideline is referenced to one of two tones of equal amplitude. The ARRL PEP spec is 6 dB lower.

73, Adam VA7OJ/AB4OJ



Title: RE: Ham Xcvrs' and Amps', Transmit Spectral Purity, IMD Products, vs. comm/maritime
Post by: VK3BL on June 15, 2018, 11:57:40 PM
Find me a single example of a 12V Ham transceiver where 5th order products (2 tone) DONT dominate at full rated output....

The reality of white noise or SSB voice is different, however.

Hi Jarrad,

Here is an example of a radio I tested in which TX IMD5 < IMD3.

http://www.ab4oj.com/icom/ic7600/7600notes.pdf (http://www.ab4oj.com/icom/ic7600/7600notes.pdf)  p. 21

All this fuss about IMD performance of amateur transceivers overlooks the fact that the ITU-R guideline (SM.326-7 §1.2.3) specifies -25 dBc for single-channel J3E, and -35 dBc for B8E (ISB). This is quite modest. I do not think an OEM will 'bust its hump' trying to exceed this guideline unless the radio set is type-approved for radio services requiring a tighter transmit IMD spec.

73, Adam VA7OJ/AB4OJ


Nice find.

Its interesting that my IC-7610 testing at full output doesn't mirror that, given the PA stage is the same I am lead to believe.

I will have to test my current radio again.

I agree there is much fuss about a natural part about radio, and people frequently misinterpret the manufacturer spec of -30 and the real life performance of some stations at -10.

73,

Jarrad VK3BL


Title: RE: Ham Xcvrs' and Amps', Transmit Spectral Purity, IMD Products, vs. comm/maritime
Post by: SM0AOM on June 17, 2018, 01:00:37 PM

2.  The RF final amps in radios and external "linear" amps were as dirty as heck (usually push-push architecture with just over 180 degrees of conduction angle), but they had the major advantage of a tuned, narrowband relatively high Q filter (tank circuit) right after them, vs. a broadband amplifier with "no-tune" broadband filters on the output.


The IMD and close-in noise of linear amplifier chains is quite unrelated to the existence of any tuned filter at the output of the amplifier. No realisable filter would be narrow enough to suppress IM3 or IM5 products, and noise within +/- 1% or so from the centre frequency.

Instead, the good IMD and noise (both close-in and broadband) performance of professional-grade equipment comes out of other design considerations:

- Gain distribution
- RF negative feedback
- Use of absorptive (harmonic dump) low-pass filters at the PA output, especially
  necessary with MOSFET and LDMOS devices
- Level setting and ALC circuits with carefully controlled dynamic properties
- Noise properties of active devices at every power level
- Noise properties of attenuators and level-control stages
- Selectivity in low- and intermediate level parts of the chain

Most amateur gear is designed with little or no concerns regarding the above,
ending up with the quite poor noise and IMD performance of contemporary equipment.

As an example, if there is improper gain distribution and lack of RF selectivity in the low-level stages of a transmitter, it is possible to end up with a transmitter that has a close-in sideband noise in the order of only - 65 or 70 dBc in an SSB bandwidth, as compared to the -100 dBc which is attainable in a top-of-the line design.

To get such performance, all parts have to be carefully engineered to reduce both the PM and AM components of the sideband noise.

In co-located systems, it often becomes necessary to limit the RF bandwidth in the low-level stages by using post-selector filters at selected points in the amplifier chain, often at the +10 or +20 dBm points before the pre-driver stage.

If one wants really "clean" signals, careful attention to detail will be necessary.



Title: RE: Ham Xcvrs' and Amps', Transmit Spectral Purity, IMD Products, vs. comm/maritime
Post by: KA4WJA on July 11, 2018, 05:02:51 AM
My answer to Brian's question is rather long...

John,
So... once again, what is the COMPELLING need to vastly improve IMD performance in good quality, modern amateur radios?  You have to find and promote those benefits, or fall by the wayside.  And let technology take it's course.

Not that I want to turn this into a rant, or anything.  :)

Brian - K6BRN

It exceeds the eham maximum length!
So, I will edit / break it up...

73,
John,  KA4WJA


Title: RE: Ham Xcvrs' and Amps', Transmit Spectral Purity, IMD Products, vs. comm/maritime
Post by: KA4WJA on July 11, 2018, 05:05:07 AM
Hello again,

Up front, I stand behind my desire that we could have HF ham transceivers that meet the old FCC Part 80 spec...but, I'm not holding my breath!  :)   So, I won't rant on about that!
Although, as I wrote before, we can make things better than they are!
We could even just use some round numbers, and pick 'em as a minimum standard....
I've advocated "40, 50, 60, 70"....meaning IMD3 in the 40's db(PEP);  IMD5 in the 50's;  IMD7 in the 60's;  and IMD9 about 70, or better...

Is this do-able...absolutely yes...is it affordable, yes (maybe another $50 to $100 cost for your average HF rig)....is it desirable, in my opinion, yes....is there compelling reasons to strive for this, in my opinion, yes (and that's the question I'm gonna try to answer here)

This is NOT going to be a re-hash of the past!  (You're welcome. hi hi)  
And, I'm not using any radios as specific goals, nor bashing any particular radios, but rather just my own personal experiences (hearing splatter and reading test results), as well as using some publicly-available images to compare / contrast...without going off on any rants!  :)

{oh, and I won't be engaging in any arguments....some may disagree with me, and that's okay with me....I'm just back here to answer Brian's legit question...:)  This might be long....but should be fairly non-controversial!!}

A few weeks ago (in an associated thread), Brian, K6BRN, asked me what are the "compelling" reasons to improve transmit IMD in our modern amateur HF transceivers...

John,
So... once again, what is the COMPELLING need to vastly improve IMD performance in good quality, modern amateur radios?  You have to find and promote those benefits, or fall by the wayside.  And let technology take it's course.

Not that I want to turn this into a rant, or anything.  :)

Brian - K6BRN

Although, I thought the reasons I had already written of (reduction of splatter helps everyone; many of the prominent voices in ham radio have been encouraging better transmit IMD for many years; and that I personally have been splatter on by hams running barefoot as well as some who obviously were over-driving their rigs and/or amps, etc.) were compelling, I replied that I would post some clarifications and scans/info that might further help show why this is compelling to me and many others....and I will do so here.

   But, there is a more-than-minor issue with this....in that what I (and others) might feel is "compelling", some others may not....some may just say "oh, that's interesting" and roll-their-eyes,  and some may disagree and say "just teach everyone how to operate [like turning their mic gain down], and everything will be fine"....others might just assume that since the rigs are allowed to be sold (in the US, EU, Japan, etc.) that they must be "just fine" (all-the-while forgetting that there are no gov't regulations on amateur radio transmitters' IMD, as it is up to us, the operators, to assure we don't cause interference to others), and as such think that I'm some "nut" who is off on a rant.  :)
     So, while I could re-post spectral scans, and re-post test result numbers, and reiterate that while I agree that some of the splatter is from operators who have maladjusted stations (mic gains and over-driving of amps), but the fact that much of the splatter we...well, at least much of the splatter that I experience (on non-contest weekends) is from radios operated as prescribed....but, to what end??

How do I show more compelling reasons than I (and others) have already shown??  And, certainly not wanting to start ranting on and on...  So, really....since the definition of "compelling" is going to be different to everyone, what/how to do this??  Hmm??


I put some thought into it...and while I could easily show 'ya live in a video presentation, etc., I just don't have the time for that.  So....in addition to all the factual data and technical discussion already posted here, I came up with 3 short / basic, and direct, ideas....maybe some will find 'em helpful, and some may even find these things "compelling"....(but, I assume, some will not....and again, that is okay with me....as I've done the best I can with the time I have for this...)

1-  Tell more of my own personal experiences...(I almost always eschew any anecdotal / personal experiences in technical discussions....but maybe that's my problem here??  I posted lots of facts, but little of a personal nature that showed how/why this is important??)

2-  Reference more of what Rob Sherwood, NC0B and Tom Rauch, W8JI, Tim Duffy, K3LR, etc. (and other contesters and prominent Dx'ers) have been saying now for years....(I usually don't like touting endorsements from others as support in technical discussions, as I prefer the facts....but, here again, perhaps I should've just done this??  Maybe if some read words from someone they trust, they'll believe it??)

3-  Show some comparison scans (that are available to all, in the public domain) of some real radios, and use some easy "round numbers" to compare and show differences and examples of what happens on-the-air (my apologies up front, to the purists...but we've already delved into the minutia, so let's leave all that on the earlier pages, yes??)  This third point is rather time-consuming and redundant (I already posted quite a few), but maybe if I draw some lines, and write some round-numbers out, showing what is happening....perhaps this will help with clarifying there are compelling reasons to care about transmitting a clean signal and not splattering??

~~~~

Okay...Before diving in, let me clarify that (in my opinion) this is not an issue to panic over!   So, please allow me to preface this whole post, paraphrasing/quoting myself, from earlier this year:

Here is what I wrote, and I still believe all of this:
Quote
....I know this isn't "global warming" or "election tampering", or even despicable leaders using chemical weapons, nor rogue states threatening nuclear attack, etc...and understand that I use lots of solar energy on my boat (where I do most of operating from, using my M-802's), don't use energy frivolously, I pay attention to political issues, elections, etc. do my homework and vote carefully, and I am horrified by SARIN gas being used openly (and glad my late father didn't live to see this, as he risked his life fighting so nobody would ever suffer this horror again), but poor transmit IMD, etc. [??? Is this really something to waste my time on?] is an issue that effects all users of our HF bands, and unfortunately many (most) are actually unaware of what their transmitters are doing...and I don't think that it is beyond the limits of "good engineering" and "good amateur practice" to try to learn more about this and to teach others as well, and truth be told, in my opinion, it IS "good engineering" and "good amateur practice" to learn these things and pass on this knowledge to our fellow hams!

Maybe from the outside it looks weird, but it looked weird to many hams 20 - 25 years ago, when some hams were very frustrated with noisy receiver oscillators, and poor (to non-existent) 1st IF filtering in "modern" rigs, and many of these guys were thought of as "obsessed with receiver IMD", but if it were not for them, we'd all be using receivers like the KWM-380 (anyone ever listen on one, on a busy contest weekend? 'cuz I have, and it was crap!! Heck, it was crap just on an average weekend!)
 
{BTW, it was some of these same hams, that back in the 1970's, started commenting on how it is our transmit IMD that is the limiting factor in our SSB Phone operations, not the better receivers of that day!!  See below for those quotes) }

And, another quote of mine, from earlier this year:

....since most never hear themselves on-the-air, and darn few ever hear what their own transmitter does on freqs +/- a few khz (or worse +/- 10 to 20khz), the actual transmit IMD and spectral purity of our signals tend to get over-looked...and that is a shame!

But, the simple fact is that the limiting factors in most of our HF receivers these days are:

a)  The transmit products (IMD for SSB and digital modes and wide-band noise/transmitter phase-noise, primarily effecting CW) of all the other stations on-the-air....

b)  Local noise levels / RFI (caused by all the misc RF radiating products around us these days)

The limiting factors are NOT how good the 3rd-order IMD spec is on your receiver...although in some very rare instances (probably < 0.1% of hams), this can be a factor, but even then not the only one...

I hope this info here helps some of my fellow hams understand what our modern HF rigs are doing to pollute the airwaves, even if they're operated with "good amateur practice", in accordance with the factory operations manual, etc...(now, if you crank-up the mic gain on most rigs, things will get worse....and many times, they'll get really bad....but, if you start with a bad rig, things get really bad very quickly...and if you start with a good rig, things might be "okay")

Starting with point #1:

I was home for a few days at the end of this past month, and I grabbed a quick look at some old logs and notes...I found some references that jogged my memory, and together with some more recent experiences, I think some may find this explanatory? (maybe even compelling? :) )

Here are some quick facts (no long ramblings) of my personal, on-air, experience (mostly nighttime 75m and daytime 20m SSB;  and early morning / later afternoon 8mhz and 12mhz maritime bands), I've made notes/comments (and some long-time memories) of splatter on the HF bands (operating from both my home station and from my boat) from:

--- Two Flex-1500's in QSO with each other (one barefoot / 10 watts, and one driving an amp)

--- Icom IC-7000's (a few different occurrences)

--- Yaesu FT-1000 (yep, that's right, an FT-1000, but only remember one)

--- Yaesu FT-857's (quite a few!)

--- Elecraft K3  (a couple times, some driving an amp, some barefoot)

--- Icom IC-718, IC-7200's (a couple different times, and one driving a SS amp on the maritime bands!)

--- Yaesu FT-2000's or 3000's ?? and FT-1200's (a few of each)

--- Icom IC-706 (a few)

--- another "Flex" (don't know what model)

--- Kenwood TS-590 (driving a solid-state amp)

Please understand that none of the splatter I experienced from these incidents listed here was due to my own rig's receiver...I know the difference, and know how reduce RF gain (actually rarely have the RF Gain at max) and to place an atten in-line (have a jumper on rear-panel of TR-7 for this, if needed)....and more importantly these were not incidents were these stations were so close as to be inside my passband, most were 5khz+ away...

Aside from this one notation of a guy with a TS-590, and one guy on the marine bands with a TS-50 many years ago, I don't think I've ever been splattered by a Kenwood, and never by Collins, Drake, JRC!! nor even TenTec (although TenTec never appealed to me, they did make nice rigs!)...

A couple of the IC-7000 and IC-706 incidents were on the marine HF bands...And, although they were not as bad as the FT-857, they weren't very good!  :)  {in addition, over the years, there have been more than a few incidents of low-voltage instability / "FM'ing" with some IC-706's and TS-50's, but these are not directly applicable to this discussion}

Here are some details about an FT-857 on the marine bands...from what I wrote earlier this year:  
Quote
Late afternoon, about 5 years ago (a few instances of this, actually spurred my research and was some of the impetus for me starting this discussion here), I was on 12.359mhz, with two 1Kw SSB stations on 12.362mhz and 12.365mhz (both approx S-5 to S-7), and never heard any artifacts / IMD from them when I was on 12.359mhz, they were only transmitting for about 7 minutes, on a regular schedule top and bottom of the hour, and I use 'em to check propagation....later, after they left the air, a station on 12.353mhz came on, and there was so much splatter on 12.359mhz, that I could no longer copy the weaker stations (mostly vessels sailing across the Atlantic) I was passing traffic for / assisting with weather info, etc., and the offshore weather net closed early that day (and the next day as well, due to the interference from these same folks)...this was a 100-watt station (from another boat, his signal on 12.353mhz was about S-5...found out later he was approx 1000miles from me, running an Yaesu FT-857), he was calling another boat and the other guy was weaker (he was running an IC-706, and was about 700 miles from me).   Understand that maritime channels are 3khz apart, and we were separated by two channels, 6khz....and the splatter from that 100-watt FT-857 was so bad that those running type-certified marine rigs 6khz away couldn't continue, as the splatter was right there inside our passbands, in our channel....but, the commercial 1Kw maritime transmissions 3khz and 6khz above us, were not interfering at all!!  (yes, the splatter was still there, even without the other stations on 12.362 and 12.365....just in case anyone thought this could've been some IMD being caused by the other stations' signals and the guy w/ the FT-857)

Another instance on this same weather net but during a morning sked, found a station on 12.350mhz (a non-standard freq) splattering badly...his signal on 12.350mhz was strong (S-7+) but sounded processed and a bit too high mic gain...but his splatter made the morning check-ins 9khz away, difficult...found out later (he told me openly) that he was running an Ameritron ALS-600 amp (he said he was getting 700+ watts out, maybe but I had my doubts as I thought it would soon melt at that power level??), and when I commented that he was flat-topping and seemed severely over-driven, he just said "oh" and changed the subject..
{BTW, even though I don't really use them much anymore (I use my M-802's) I found my old notes, from tests of my own TR-7, back many years ago... -38 / -44 / -52 / -58 db(PEP), at 100 watts, measured in a lab with an old HP 141/8553....not stellar, but better than almost all of today's rigs....about 10db better than the average of today's rigs...and 15db better than some of today's rigs!}


So, onto point #2:

(con't below)

73,
John,  KA4WJA


Title: RE: Ham Xcvrs' and Amps', Transmit Spectral Purity, IMD Products, vs. comm/maritime
Post by: KA4WJA on July 11, 2018, 05:07:23 AM
(Con't from above)



So, onto to point #2:

Some hams (and many new hams) seem to assume the "Sherwood List" is like a stone tablet of what are the "best radios", which is so ironic (and surprising to many, me included), 'cuz if you actually read what Rob, NC0B writes and listen to what he says, he never says anything like that.....his list is NOT a list of the "best radios", rather just a listing of radios that he has tested, organized into a hierarchy based on "close-in (2khz) receiver IMD test results" (and with many of the rigs on that list for years, also being noise-limited...aka RMDR-limited...rather than limited by their 2khz receive IMD spec)...

If you read some earlier posts, you'll see some recent quotes from Rob (and look at some other prominent contesters, too) regarding the fallacy of the "best radio", and most importantly see that he (and many others) found out long ago (and have publicly-stated for many years) that it is our transmit IMD (and for CW operations, transmit phase noise/osc sideband noise) that is the true limiting factor in almost all real-world, on-air, situations!!!   It is not our receivers!!

https://www.eham.net/ehamforum/smf/index.php/topic,97093.msg1053647.html#msg1053647

{of course operator adjustments, like cw rise-time/keying shape (for CW operations) and mic gain settings (for SSB and many digital modes), are a part of the problem...and this not made light of, but rather pointed out clearly....it's just that there are radios and some radio settings/adjustments (like ALC) that even when operated as proscribed in their manuals, produce seriously inferior transmit signals with rather poor IMD...as well as the ALC-overshoot issues, causing lots of popping/spurts, etc., and these overshoots are even causing quick transients with amps, as these are short periods of severe over-drive...}

With a very few exceptions, just about any modern HF ham rig (made in the past ~ 40 years) has adequate receiver IMD specs to survive just fine on our SSB Phone bands...(and most of the better ones' receivers do well, even in crowded CW bands)....but many of these rigs' transmitters produce rather poor IMD!  :(

Here is a direct quote from Rob Sherwood (back then WB0JGP), from 1977!  Yes, that is correct 1977, not a typo!!  Yes, that's 41 years ago!! {yes, I was reading and learning about IMD, back in the mid 1970's....joined ARRL in early '74...read a lot..a lot! includ. papers by Bob Sutherland, W6UOV/W6PO;  Eimac;  Bill Orr;  etc. I subscribed to the "Lunar Letter", too!..actually moonbounce/EME was one of the things that spurred my interest in ham radio...but also the technical side of things, like how to get your signal thru (both by using the proper antenna for the freq and path of communications, as well as by making sure your signal was "efficient" i.e. "clean"!)....it was later, in the 80's, that I learned about the advantages of separate rec ant, etc....oppss, sorry for the digression!}

So, in addition to his more recent public postings of the last 10 years, or so (see some quotes of his, in my earlier posts here https://www.eham.net/ehamforum/smf/index.php/topic,97093.msg1053647.html#msg1053647 ) regarding our transmitters' IMD being the limiting factor in our use of the SSB Phone bands, not our rec specs, here is Rob Sherwood, from 1977 (in reference to SSB phone operations), in Dec 1977 "Ham Radio" Magazine:

Quote
Generally speaking, transmitted IMD from an rf power amplifier [exciter] will be worse that that internally generated in the receiver, with the result that the transmitted IMD may cover up a receiver's shortcomings.
 (there is a lot more...but, I'm not going to reprint the whole article...)

This was where the primary focus was improving close-in (2khz) receiver IMD, for CW contesting, in 1977 (before the days where we had "phase noise" issues), but their work and words also took into account the transmitter's spectral purity, and when dealing with (their lesser-important concern)  SSB Phone operation, they wrote some paragraphs about the transmitters' IMD being the limiting factor, not the receiver IMD specs....

And that was back in the mid/late 1970's, where some good receivers had 70db to 80db "close-in" IMD3 specs, and only a few like the Drake TR-7, and JRC's, etc., had 95db to 100db "wide"/20khz IMD3 receivers! (but Signal One's and TS-830's came close) and then 10 years later the IC-781...followed by the TT Omni's, IC765, etc...

{Anyone ever wonder why, even now in 2018, the old venerable TR-7's IC-781's, JRC's, Omni's, 830's, etc. are used (and highly regarded) in serious SSB operations, even in some SSB contests....'cuz they're great rigs, and except for some older ones having some synth phase noise issues / noise-limited rec IMD (RMDR) they all have great receivers (even by today's standards)....and it's not by coincidence that they have great transmit audio and decent transmit IMD..  Heck, most seasoned hams would say the TS-830 is the best Kenwood ever made (and the 930 or 940 is in second place, and you don't find them on the top of Sherwood's list, hi hi.)...and while the JRC's were never big sellers here in the USA, they do work very well on both rec and xmit!!....the TR-7, IC-781, and the TT Omni's, (along with the 830's and JRC's) all do daily service in crowded phone bands, and hold their own, even in SSB contest environs....and except for the extremes of 160m CW contesting, I hear they all still work well (ok) in some CW contesting, too! :)

The main reason that some of these old rigs are being "retired" to an upper shelf in SSB contesters' shacks is because they have no "band scope" or "waterfall" display, nor computer control, etc., and it seems that without those technological advances many have trouble with SSB Contesting?? Especially S&P...(guess technology moves on, huh?)  It's not because these rigs can't cut the mustard anymore, nope they still do that...it's 'cuz some want a "tech advantage" / more features!  :)

Those hams that know, know!  What's that old Alpha ad say?  "Ask the ham that owns one."....

Well, ask the hams that own/use some of these rigs on our SSB phone bands....and I think you'll find a surprising consensus:  They're all darn good rigs...and some of 'em have good transmit IMD specs (look at those JRC's and that wonderful TS-830), certainly better than today's rigs....and it's not a coincidence that those that know, use them!  (heck, Rob Sherwood's favorite SSB rig is his IC-781....although I don't use it often, mine is my TR-7....and we can afford whatever new rig we want)....it's not nostalgia, or old guys being stuck in the past, it's because they're darn good radios, even by today's standards, and again it's not coincidence that they have fairly good transmit performance / decent transmit IMD (compared to some of our modern rigs)...

Please read some of Rob's other quotes (in this earlier post), where he mentions the transmitter IMD being an important factor....and limiting factor, on our SSB Phone bands these days...

Onto Point #3:

(con't below)

73,
John,  KA4WJA


Title: RE: Ham Xcvrs' and Amps', Transmit Spectral Purity, IMD Products, vs. comm/maritime
Post by: KA4WJA on July 11, 2018, 05:08:44 AM
And, now for #3:

Please know that while I'm posting some Spectral Scans (and real-world explanations), this is not intended as a seminar, nor treatise, on transmit IMD....I don't have the time, nor software to do it justice...no powerpoint and no photoshop...just a couple pics from NC0B's talks (some courtesy of W6XX), etc., with some of my crude drawings to help...[Please forgive my crude drawing, and understand these drawings are not precise/absolute!]

Also, please note that I debated whether to use just the few scans using white noise, that I have, rather than try to use some two-tone scans (and draw-in the actual occupied bandwidth)??  If I use some two-tone scans and draw stuff in, some will just cry foul and some/much of all this effort will be for not....and I do not wish to run off on more tangents about transmitter testing, tone freqs, etc. etc...I just want to address Brian's legit question, asking what are the compelling reasons to improve our transmit IMD / spectral cleanliness... :)

So, I think I will just include the few white noise scans and use them as comparisons, and these are NOT meant to insult any specific radio, they're just what I have available....hope this is okay??
Now before anyone balks, and says that striving for 60db S/N (or S/interf) ratios is a ridiculous idea on our HF ham bands...no worries here, I'm not saying that is the goal!  :)   Although, it would be nice, what I'm just saying is that we can do better than what we're being sold these days, and if we can get a 10db to 20db improvement in average transmit IMD (do-able and affordable) from our HF rigs, the bands would be easier to use, and friendlier, too!  :)

{Although, in the world of commercial HF / maritime HF ~ 60db S/N is done all the time....we are not in that business, we're hams....and getting a 20db to 30db S/N on HF SSB, is good with most of us....but remember that there are many times where there are stations close in freq (even directly adjacent) that can be 30, 40, 50, 60db, or more, different in strength...heck, on some of my 75m operations, I've had a couple guys S-9 +30db (or more), and one or two only S-7 or less...and that's as much as 50db difference, in the same round-table!  and this is one reason that I give one or two of them some good-natured ribbing for not having a decent antenna and/or a nice amp (hi hi)....'cuz it's a pain to run the RF gain up to hear the S-5, S-6, or S-7 guys, when the others are 20 to 30+ over...:)  So, even if you think your transmitter isn't so bad, remember there are others on adjacent freqs that might be in QSO with signals significantly weaker, and your transmit IMD could be seriously detrimental to those guys!!}

[The final preface here is a reminder that these are not worst-case scenarios, but rather just average everyday situations....no extremely crowded conditions, nor seriously offensive transmit IMD, nor super wide variations in signal strengths...just showing average normal stuff, from average rigs...]

This first image (courtesy of W6XX, from a paper presented by Rob Sherwood), show two rigs running at 75w PEP....one is an FT-1000 MkV in Class A;  the other is a K3;

 (http://i66.tinypic.com/24w8tna.png)

The FT-1000 MkV in Class A @ 75 watts PEP, shows a nice clean (and narrow) spectrum...only 6khz wide, at -60db down!!! (that's about 1.6khz to 1.8khz from the transmitter passband)

The K3 @ 75 watts PEP, in comparison, is fairly wide...about 15khz wide, at -60db down...(that's more than +/- 6khz beyond the transmit passband)


This second image shows two different rigs, operated at 100 watts....one is a modern IC-7600;  the other is a bit older / legacy IC-756ProIII;

 (http://i65.tinypic.com/jai6fb.png)

The 756ProIII isn't too bad, but still pretty wide...14khz wide, at -60db down...(about +/- 5.5khz from xmit passband)

But, the IC-7600 is really wide...20khz wide, at -60db down...(that's about +/- 8.5khz from xmit passband)


In this third image, I took the original image of the FT-1000 MkV  vs.  the K3, and I drew in some other signals (red, yellow, and blue), and if the top line of the spectrum analyzer display (ref level) is at say S-9 +20db to S-9 +30db (considering approximations and normal HF fading), and the other signals, +3khz (yellow),  -3khz (red),  and -6khz (blue),  are of accordingly weaker strengths....

 (http://i67.tinypic.com/1eukup.png)

The "white" signals (at 14.200) =  S-9 +20db to S-9 +30db

The "yellow" signal (at 14.203) =  S-8 to S-9  (30db weaker than the "white" signals)

The "blue" signal (at 14.194) = S-8 to S-9 (30db weaker than the "white" signals)

The "red" signal (at 14.197) = S-7 to S-8 (40db weaker than the "white" signals)

If you look at how much of the various colored signals are "above" the "white" signal, you can see the approximate S/N, or S/I (Signal-to-Interference) of those QSO's....and you can certainly see how easy / difficult those QSO's will be...

The "yellow" QSO guys would need some IF shift and probably a narrow SSB filter to have an acceptable QSO when the K3 is transmitting....but not much of a problem, when the FT-1000 MkV is transmitting... :)

The "blue" QSO guys might be okay, when the K3 is transmitting...although, they'd still want to narrow their rec passband and adjust their IF shift a bit...

The "red" QSO is not going to be long-lived here....they'll likely QSY or they're done... :)

If you can increase power or antenna gain in the desired direction on some of the color QSO's (or, even better, if they can rotate their antennas to place their nulls onto the K3's signal), that can help...or get the "white" QSO guys to reduce their power, turn their antennas, etc...or any combination of these....this can all help...but....but, except for the "color" QSO guys turning their antennas to null out the k3's signal as best they can, there's little chance of these other things being done...

But....If you can narrow the occupied bandwidth of these transmitters, everyone's QSO's improve!!  Hmm....what a novel idea....let's reduce our occupied bandwidth / improve our transmitters' IMD, and everyone wins!!

If it was just someone's mic gain being cranked up to max, or serious amp over-drive, that would be an easy fix....but, you see these scans of transmitters are not with mic gains cranked all-the-way up...nope these are with the rigs operated as designed/proscribed....and these are the best they're gonna get!  :)  These are not worst-case....not even close....This is just "normal" / "everyday" operations....


If you want to see what it could be like, have a look at the 4th image...look at just the narrow "white" transmission (the FT-1000 MkV) and look at the dotted lines of the "color" transmissions...and what-do-you-know, you now have 4 different QSO's, at different signal strengths, all spaced about 3khz apart, and nobody is interfering with their neighbors...[Again, please forgive my crude drawing, and understand these drawings are not precise/absolute!]

 (http://i66.tinypic.com/1z67ma.png)

Hmmm....is this compelling??  Not sure about everyone here, but it is to me... :)


And, for those that might think Class A operation is needed, or that we need to go back to vacuum tube PA's....I highly disagree with both of these...(see earlier posts for info on what is easily possible to accomplish in solid-state Class B PA's)....

{I know some are waiting for all HF rigs to have active pre-distortion, but as of 2018, Apache Labs is the only one doing it...and with literally 100's of thousands of hams (millions) on the HF bands using analog rigs and/or DSP rigs, and only a couple thousand using SDR's, active pre-distortion is a LONG way from being ubiquitous!! A REALLY LONG WAY!!  So, maybe we hams can vote with our wallets, and demand better transmit IMD, now....not wait 'til some manufacturer decides they'll grace us with that "privilege"??   I mean it's really up yo us, the technology is there (been there for decades) and it doesn't cost a lot....it's up to us to demand it! }

Have a look here at this 5th image....which shows an FTdx-5000 in Class A operation...(FYI, this is a10khz wide image, rather than the above 20khz wide images)

 (http://i67.tinypic.com/rssya9.png)

Note the vast difference in the occupied bandwidth between having 1/2-scale of ALC, versus No ALC at all....

1/2-scale ALC = it's almost 11khz wide at -60db down...better than any of our "modern" rigs that have Class B SS PA's, but not what most think of as that wonderful Class A advantage..(that's because of Yaesu's ALC)

No ALC = it's only 5.8khz wide at -60db down!!!  (just about 1.6mhz from xmit passband, it's 60db down!)  And, that is very nice!!


Finally #4  (yeah, there was supposed to be only 3!)

#4 -  While I was writing all the above, it dawned on me that I probably should include a few other comments regarding a "compelling reason" to improve our transmit IMD...but some of these final points are opinion, rather than the many facts above...so, wasn't sure whether to write these or not, but here goes:

--- It makes good sense.

--- It's efficient use of the airwaves.

--- It is the polite / courteous thing to do.

--- And, that it meets 4 of the 5 basic reasons/tenants for the existence of the amateur radio service.

After all, from Part 97, the 5 basic reasons / purposes of the Amateur Radio Service are:

"The rules and regulations in this part are designed to provide an amateur radio service having a fundamental purpose as expressed in the following principles:

(a) Recognition and enhancement of the value of the amateur service to the public as a voluntary noncommercial communication service, particularly with respect to providing emergency communications.

(b) Continuation and extension of the amateur's proven ability to contribute to the advancement of the radio art.

(c) Encouragement and improvement of the amateur service through rules which provide for advancing skills in both the communication and technical phases of the art.

(d) Expansion of the existing reservoir within the amateur radio service of trained operators, technicians, and electronics experts.

(e) Continuation and extension of the amateur's unique ability to enhance international goodwill."

--- So, to advance the radio art, advance the skills in both the communications and technical phases of the art, expand the reservoir of technicians and electronic experts, and enhance international goodwill....4 of the 5 purposes above...having a clean transmitter and allowing others to use the airwaves without adverse interference, and learning about how this is done, etc., actually does accomplish 4 of the 5 of these....so...

--- How about we look at what we are trying to accomplish here...inform and educate our fellow hams, regarding reduction of on-air transmit interference (and hence allow those who bought "90db to 100db dynamic range radios", to actually get close to being able to use some of that potential).


I do hope this here, and all the rest of this thread (please read it), gives some of you compelling reasons to improve our ham rigs' transmit IMD, improve our transmit spectral purity...if not, that's okay....not going to go off on a rant, nor engage in any arguments, so I will just agree to disagree, politely.  :)

Fair winds and 73,

John,  KA4WJA


Title: RE: Ham Xcvrs' and Amps', Transmit Spectral Purity, IMD Products, vs. comm/maritime
Post by: KM1H on July 11, 2018, 06:54:46 AM
Quote
{Anyone ever wonder why, even now in 2018, the old venerable TR-7's IC-781's, JRC's, Omni's, 830's, etc. are used (and highly regarded) in serious SSB operations, even in some SSB contests....'cuz they're great rigs, and except for some older ones having some synth phase noise issues / noise-limited rec IMD (RMDR) they all have great receivers (even by today's standards)....and it's not by coincidence that they have great transmit audio and decent transmit IMD..  Heck, most seasoned hams would say the TS-830 is the best Kenwood ever made (and the 930 or 940 is in second place, and you don't find them on the top of Sherwood's list, hi hi.)...and while the JRC's were never big sellers here in the USA, they do work very well on both rec and xmit!!....the TR-7, IC-781, and the TT Omni's, (along with the 830's and JRC's) all do daily service in crowded phone bands, and hold their own, even in SSB contest environs....and except for the extremes of 160m CW contesting, I hear they all still work well (ok) in some CW contesting, too!


While Ive already mentioned that I own 4 TS-830's they arrived later in life and 3 are used only to drive VHF to microwave transverters. The other is at the amp repair, IMD test, and 6M amp conversion bench.  I did this because the pairs of TS-930 and 940's I used after giving up on a pair of Drake C Lines which became dinosaurs for contesting, had horrendous phase noise.....on TX with out any drive to the transverter/amp the wide band noise was S9 for over 20 kHz on 6M.
Being on top of a hill with 1200W and big antennas did not make me popular with the locals. The 830's were completely quiet in all respects.

While this crud was common on HF and buried during contests and DX pileups it really annoyed me.

At work I was involved in the design of RF data modems and line amps to be used over CATV cable private networks. With everything from voice to TV and high speed data all possibly running at the same time the signals had to be very clean on RX and TX.
Having many ham friends at Microwave Associates from CEO to techs we brainstormed for weeks and they finally came up with PIN diodes that would replace the common silicon and germanium diodes used for signal path switching.

I had already brought my TS-930 in on weekends to perform various KW and other mods while documenting it all thanks to a full lab of new (at the time) HP gear. Once the rig was up to the current level of KW and other knowledge the RX and TX were almost acceptable but still not close to the modified C Line.

Starting with the RX front end octave filters the PINs were used, then the crystal filter switching diodes were replaced. The first step was a major improvement and the second step was a lesser but noticeable improvement which also helped the TX side as the signal went thru the 455 kHz filter. Changing a few other diodes in the TX path and TX/RX paths brought the noise way down.

When a TS-940 replaced one of the 930's the same procedure was followed and soon both were 940's by the late 80's

Along the way I had been corresponding and talking with Ulrich Rhode who had recently purchased a new TS 440 and was following my progress while being a huge help at the same time.
After he updated his rig he tried to convince KW to make the switch but Yaesu was immediately receptive and included PINs in their new FT-1000D and offered an update kit for the early production runs. It took KW several years to wake up.

If youre not familiar with the name read this:
http://www.ece.drexel.edu/DIG/events/LectureSeries/DrRohdeBio.pdf



Quote
The FT-1000 MkV in Class A @ 75 watts PEP, shows a nice clean (and narrow) spectrum...only 6khz wide, at -60db down!!! (that's about 1.6khz to 1.8khz from the transmitter passband)

The K3 @ 75 watts PEP, in comparison, is fairly wide...about 15khz wide, at -60db down...(that's more than +/- 6khz beyond the transmit passband)

The K3 was notorious for poor SSB at first but I thought that was corrected in that model and later could be updated to the even better K3S ??

Carl


Title: RE: Ham Xcvrs' and Amps', Transmit Spectral Purity, IMD Products, vs. comm/maritime
Post by: KA4WJA on July 11, 2018, 10:12:34 AM
Carl,
Thanks for the great story!  That's really cool!

Yep I know the name, Ulrich Rhode....although never met him.
And, I will read the bio...and learn something new about 'em.

BTW, somewhere in a file cabinet at home I've got a sailing magazine article showing one of the Rohde & Schwarz family (could've been Ulrich?) on his sailboat with a complete R&S HF transceiver and 1kw SS amp, etc...this was a dozen or so years ago... (if I ever find it, I'll forward it on to ya')


73, and thanks again for the cool KW story!
(I don't have that kind of history...but do remember when we got a new 830 at our college club station at WPI, W1YK...we had a nice 4-1000 amp, w/ a BIG PS and 6Kv on the plate....with lots of great monobanders, etc...was a cool station to have fun at, as a young ham....and my best friend bought and restored an 830 a dozen years ago, and loves it....nice audio and nice signal on 75m, as he uses my spare amp, SB-221...)

John,  KA4WJA


Title: RE: Ham Xcvrs' and Amps', Transmit Spectral Purity, IMD Products, vs. comm/maritime
Post by: KM1H on July 11, 2018, 11:23:36 AM
You mean this John?

http://www.n1ul.com/

How about an answer to my K3 question?

Carl



Title: RE: Ham Xcvrs' and Amps', Transmit Spectral Purity, IMD Products, vs. comm/maritime
Post by: KA4WJA on July 11, 2018, 01:16:38 PM
Carl,
Yep, I think you might have found his boat...
This sailor (Rhode?) was on his sailboat, and he had a complete R&S  HF set-up...but I thought he had a 1kw amp on-board?  Maybe not....maybe my memory is wrong...
But, whatever....that Nav Station (radio room) looks AWESOME!! (mine isn't that nice!)

I will still look for that article, next month.
I think it was in Blue Water Sailing Magazine??  About 10 years ago??
But, it looks like you found his boat!  Cool!



As for the K3....I know you don't like ARRL numbers, so wasn't going to delve into that....but, since you asked again...here goes.

While Elecraft supposedly did make some changes to their PA for the K3s, it doesn't appear to be much of an improvement...and unless the 11th and higher order products are way down (I don't know, I have no test results past the 0th), the new K3s is actually a bit worse than the original K3.

{These ARRL numbers are:  3rd, 5th, 7th, and 9th order, in -db(PEP), as published in QST}

Elecraft K3
-33 / -40 / -48 / -50

Elecraft K3s
-30 / -38 / -41 / -48  

After the ARRL informed them that the K3s' transmit IMD was worse than the original K3....Elecraft sent the ARRL lab a new and specially-tuned / aligned K3s....give the ARRL lab credit for openly writing about the whole ordeal in QST...see Nov 2016, QST, page 50, for details.
(but, it's a shame Elecraft hasn't really made SSB operation a priority, and as such hasn't done much to improve their 12v PA)


And here are their test results, with the specially-tuned and aligned PA...(nothing special at all....and except for a 12db improvement in 9th order products, the K3s is worse than the original K3.)

-35 / -36 / -48 / -62 (specially tuned transmitter and PA, by Elecraft engineering dept, after the above disappointing results were reported, prior to publication, again see Nov 2016, QST, page 50, for details)


73,

John,  KA4WJA

P.S.
Everyone please remember that I'm not trying to insult any radio, especially not Elecraft...I just used the rigs that have been used in public discussions and ham radio seminars, that I had access to white noise IMD test results..

P.P.S.  Here is my "radio room" on-board:

http://www.c470.jerodisys.com/470pix/4700302.htm

http://www.c470.jerodisys.com/470pix/4714801.htm

http://www.c470.jerodisys.com/470pix/4700307.htm



Title: RE: Ham Xcvrs' and Amps', Transmit Spectral Purity, IMD Products, vs. comm/maritime
Post by: KM1H on July 11, 2018, 06:12:19 PM
Nice layout and thanks for the K3 info and its a shame Elecraft has no interest in producing a clean radio.

This should keep you entertained for awhile

http://saildragonfly.com/

Ulrich has never been known to do anything half assed and Ive known him for several decades......He is 7 months older than me and doesnt let me forget it.

My family on my mothers side is also from Bavaria and my #2 son lived in the Austrian border region after retiring from the USAF for about 4 years but the costs were too much and he is now in Montenegro on the coast with his Russian GF and her son....life is so hard when the beach is a few minutes walk away ::) ;D  We visited last year.

Carl


Title: RE: Ham Xcvrs' and Amps', Transmit Spectral Purity, IMD Products, vs. comm/maritime
Post by: HAMHOCK75 on July 12, 2018, 07:53:42 PM
Quote from: KM1H
If youre not familiar with the name read this:
http://www.ece.drexel.edu/DIG/events/LectureSeries/DrRohdeBio.pdf

This brought back a lot of memories. I was introduced to Ulrich Rohde in the mid 1970's when he visited our facilities in Palo Alto. Unfortunately, I could not discuss anything technical with him. My superior at the time ( also an engineer from Germany ) warned me not to say or reveal anything technical because he had been sent by Rohde & Scharz to set up their first sales office in New Jersey. Rohde & Scharz was our strongest competitor in Europe at the time.

I was also told that he and his more famous father were not on the best of terms resulting in his assignment over here.

I also worked with George Vendelin. George is very good at cajoling people into helping him with his books, lol!


On another note. Were you suggesting that the use of pin diodes reduced noise or intermodulation products in the TS930?


Title: RE: Ham Xcvrs' and Amps', Transmit Spectral Purity, IMD Products, vs. comm/maritime
Post by: K6BRN on July 13, 2018, 08:58:51 AM
Hi John (KA4WJA):

I've not visited this bizzare thread in a while and was sitting here, having breakfast in Vegas as reading the news when I jumped over to eham and cought your replies.  I read them.

You probably could have summarized the entire rambling response in three sentances - so I guess you have a great deal of time on your hands, which is just fine.

Your point regarding conservation of bandwidth just does not strike a chord with me.  Amateur bands are already minute in the overall ITU spectral plan and within these minute slivers they are barely used.   And in a contest, battles over making the contact will make ANY local bandwidth scuffle pretty intense regardless of minor spectral broadening (or not) and STILL leave most of the amateur band unused.  So a slight widening of signal bandwidth due to less than ideal IMD on the part of the transmitter and amp is just not terribly important.  Gross widening, yes.  A little... who cares?  Try designing a commercial system to work under Volna band constraints - now there's a challenge.  And a reason for heroics.  On AMATEUR radio...  why?

Gross splatter due to amplifier overdrive (why don't you simply advise amateurs to back off power by 2--3 db from max), audio overdrive, poor tube amp tuning, etc.  that can be REALLY annoying is probably a more productive pursuit.  And it happens all the time on amateur radio and can be improved with education.  What a thought.

Best Regards, Captain...   In a way you were responsible for bootstrapping my early career...   but that's another story.

Best Regards,

Brian - K6BRN


Title: RE: Ham Xcvrs' and Amps', Transmit Spectral Purity, IMD Products, vs. comm/maritime
Post by: KA4WJA on July 13, 2018, 09:33:18 AM
Brian,
No worries.

You asked for compelling reasons, and I tried.
And, it really didn't take that long....except for my "all thumbs" approach to 3D Paint software to draw / type on top of the spec analyzer scans.....everything else was just off-the-top-of-my-head, one evening.

Maybe it will help someone?

Take care.

73,
John,  KA4WJA


Title: RE: Ham Xcvrs' and Amps', Transmit Spectral Purity, IMD Products, vs. comm/maritime
Post by: SWLER1965 on September 24, 2018, 05:52:37 PM
Ka4wja,
Thank you and everyone else too.


Hello to all,

I suppose that since most never hear themselves on-the-air, and darn few ever hear what their own transmitter does on freqs +/- a few khz (or worse +/- 10 to 20khz), the actual transmit IMD and spectral purity of our signals tend to get over-looked...and that is a shame!

But, the simple fact is that the limiting factors in most of our HF receivers these days are:

a)  The transmit products (IMD for SSB and digital modes and wide-band noise/transmitter phase-noise, primarily effecting CW) of all the other stations on-the-air....

b)  Local noise levels / RFI (caused by all the misc RF radiating products around us these days)

The limiting factors are NOT how good the 3rd-order IMD spec is on your receiver...although in some very rare instances (probably < 0.1% of hams), this can be a factor, but even then not the only one...

I hope this info here helps some of my fellow hams understand what our modern HF rigs are doing to pollute the airwaves, even if they're operated with "good amateur practice", in accordance with the factory operations manual, etc...(now, if you crank-up the mic gain on most rigs, things will get worse....and many times, they'll get really bad....but, if you start with a bad rig, things get really bad really very quickly...and if start with a good right,  things might be "okay"

I'm new to ham n looking to figure out what radio n antenna I need,  this is very helpful cuz I never realized how important my radio is n how important it's adjustments are to others trying to use the airwaves.

Thank u for all of this. Especially those quotes cuz they're teaching me there's a lot more to ham radio than I thought.

A future ham n long time SWLR


Title: RE: Ham Xcvrs' and Amps', Transmit Spectral Purity, IMD Products, vs. comm/maritime
Post by: G3RZP on September 25, 2018, 05:48:47 AM
I have a lecture which I do for radio clubs and first did at the RSGB Convention 5 years ago. In it, I analyse the QST published IMD results of 142 transmitter/transceivers introduced since 1972 and one thing stands out like a sore thumb - high order IMD got far worse after the move to solid state PA stages.

The average of tube PA tx was 3rd at -36, 5th at -44, 7th at -58, 9th at>-66

The average of SS PA tx was 3rd at -30, 5th at -41, 7th at -47, 9th at -52

Which you could expect from the expansion of log(cos f1 + cos f2)

The Anan 600 with pre-distortion is an exception.... but I don't know how good it is on wide band noise. Both Cartesian and Polar Loop  approaches offer very good IMD, but  do have problems with wide band noise from their mixers.

I do agree that most reception failure factor is caused by external noise of one sort of another - tx IMD, tx  wide band noise and external wide band noise for all sorts of electrical and electronic equipment. I have been told that the SARSAT authorities are getting worried by the amount that the 406 MHz noise floor has gone up.


Title: RE: Ham Xcvrs' and Amps', Transmit Spectral Purity, IMD Products, vs. comm/maritime
Post by: KA4WJA on September 25, 2018, 11:16:41 AM
Jon,
I'm glad you found this helpful... :)

Ka4wja,
Thank you and everyone else too.


Hello to all,

I suppose that since most never hear themselves on-the-air, and darn few ever hear what their own transmitter does on freqs +/- a few khz (or worse +/- 10 to 20khz), the actual transmit IMD and spectral purity of our signals tend to get over-looked...and that is a shame!

But, the simple fact is that the limiting factors in most of our HF receivers these days are:

a)  The transmit products (IMD for SSB and digital modes and wide-band noise/transmitter phase-noise, primarily effecting CW) of all the other stations on-the-air....

b)  Local noise levels / RFI (caused by all the misc RF radiating products around us these days)

The limiting factors are NOT how good the 3rd-order IMD spec is on your receiver...although in some very rare instances (probably < 0.1% of hams), this can be a factor, but even then not the only one...

I hope this info here helps some of my fellow hams understand what our modern HF rigs are doing to pollute the airwaves, even if they're operated with "good amateur practice", in accordance with the factory operations manual, etc...(now, if you crank-up the mic gain on most rigs, things will get worse....and many times, they'll get really bad....but, if you start with a bad rig, things get really bad really very quickly...and if start with a good right,  things might be "okay"

I'm new to ham n looking to figure out what radio n antenna I need,  this is very helpful cuz I never realized how important my radio is n how important it's adjustments are to others trying to use the airwaves.

Thank u for all of this. Especially those quotes cuz they're teaching me there's a lot more to ham radio than I thought.

A future ham n long time SWLR

FYI...I know there is a lot here...probably WAY too much??  hi, hi...

But, if you (or any of my fellow hams) scrap off the fluff, here's the gist:

1 --- Most (all?) modern SS rigs have worse transmit IMD than what we used to have back 40 years ago, or longer...(and it's up to us to force improvements from the manufacturers)

2 --- Some modern rigs are better than others in this regard, and while "high-voltage PA's" (50vdc) can help, this is shown to not really be the determining factor on which rig is "clean" versus which ones are "dirty"...

3 --- Some modern rigs are really crappy....(and, if operated improperly can really be a major problem)

4 --- Just about any modern ham rig can be made to produce a dirty signal / splatter up-n-down the band....by cranking up the mic gain;  and/or twiddling with other internal adjustments;  and/or overdriving of external amps, etc.....but, even when operated properly / as prescribed by the manufacturers, some rigs are just crap....and darn few (none?) meet what most hams consider "good engineering" and "good amateur practice"...

5 - And, finally....and most importantly....
The limiting factor in our modern HF SSB rigs' receivers is the transmit noise / transmit IMD of the other rigs on nearby / adjacent frequencies!!  It is not whether or not you have a "100db dynamic range" radio, but it is how clean are the other transmitters on-the-air when you are trying to operate!!

{"70db - 75db receivers" work fine in ham radio SSB service...with "80db" rigs being good for most other operating....except for the extremes of CW contesting or in CW Multi-Multi contest environs, where some just might be able to utilize a 90db to 100db dynamic range receiver....with the transmit noise of all the other stations on nearby / adjacent freqs, it just isn't possible to utilize a "100db" dynamic range receiver in 99.99% of ham stations...
But, if we can "clean up" the airwaves a bit....or at least don't let it get any worse.....we might be able to use some of the range of the receivers that so many hams have paid for!!  :)}


{although I was only looking at SSB, etc. operations, we also touched on the fact that some modern rigs have significant transmit wideband noise / high noise sidebands, that seriously widen their CW bandwidths as well...along with fairly sharp/harsh CW-keying waveforms, these are the major factors effecting how good of a CW receiver can you actually use....although there has been some improvement in these areas by Elecraft, etc....spurred-on by the CW contest environment....the same has not happened to the transmit PA designs, nor the crappy ALC designs, in many of our "modern" rigs, which is why it is up to US (me and my fellow hams) to "force" improvements!!


Okay, enough rambling....I think you all get it... :)


~~~~~~~~~~~


BTW, Peter, I think it was I that mentioned this here in this tread....
I have been told that the SARSAT authorities are getting worried by the amount that the 406 MHz noise floor has gone up.
In addition to the COSPAS-SARSAT (at the int'l protected 406mhz), both Iridium and INMARSAT have engineers studying the link budget issues brought on by increased terrestrial background noise at L-band!!!  :(


73,
John,  KA4WJA


Title: RE: Ham Xcvrs' and Amps', Transmit Spectral Purity, IMD Products, vs. comm/maritime
Post by: K6AER on September 25, 2018, 02:25:32 PM
I thought L-band was from 1-2 GHz.


Title: RE: Ham Xcvrs' and Amps', Transmit Spectral Purity, IMD Products, vs. comm/maritime
Post by: KA4WJA on September 25, 2018, 02:35:31 PM
Mile,
You are correct...
I thought L-band was from 1-2 GHz.
That's why it is so staggering that we are seeing increased terrestrial background noise being received by satellites with their antennas point at the earth...
INMARSAT and Iridium use L-band (actually their uplink/downlink bands are adjacent / straddle each other....from 1525mhz thru 1660mhz)....
And, in addition to their engineering groups, they're in contact with ITU working groups, etc. to assess how-to reduce the hoards of un-certified (or just self-certified / BS'ed paperwork) consumer electronics populating the world, causing the rise in our background noise!!  :(

Now, if we hams want to help ourselves....well, then that is up to us... :)


73,
John,  KA4WJA


P.S.  Of course their is also, Globalstar [sic], and Thurya, on L-Band...as well as other regional (and global) mobile satellite communications systems, some using VHF and some using S-Band....


Title: RE: Ham Xcvrs' and Amps', Transmit Spectral Purity, IMD Products, vs. comm/maritime
Post by: G3RZP on September 26, 2018, 02:06:23 AM
A little ironic that Iridium is having problems - it was spurious emissions from Iridium satellites interfering with Radio Astronomy on 1420 MHz that led way back in 1993 to the WRC charging ITU-R Study Group 1  with setting up what became Task Group 1/5 to revise Recommendation SM329 on Spurious Emissions.


Title: RE: Ham Xcvrs' and Amps', Transmit Spectral Purity, IMD Products, vs. comm/maritime
Post by: KM1H on September 26, 2018, 08:39:13 AM
A little ironic that Iridium is having problems - it was spurious emissions from Iridium satellites interfering with Radio Astronomy on 1420 MHz that led way back in 1993 to the WRC charging ITU-R Study Group 1  with setting up what became Task Group 1/5 to revise Recommendation SM329 on Spurious Emissions.

And the circle of unintended consequences continues ::)


Title: RE: Ham Xcvrs' and Amps', Transmit Spectral Purity, IMD Products, vs. comm/maritime
Post by: SWLER1965 on October 01, 2018, 12:35:45 PM
With the kids out of the house I hope to have the time to learn but wow I've got a long road ahead.   Thank goodness for Google

Thx to u all
Jon


Title: RE: Ham Xcvrs' and Amps', Transmit Spectral Purity, IMD Products, vs. comm/maritime
Post by: KA4WJA on October 15, 2018, 04:45:47 PM
FYI, here are some updated / corrected transmit IMD figures for the Apache Labs ANAN-8000DLE (form Nov 2018, QST)

As for the ANAN-8000DLE....it's a nice rig (just wish it had "knobs"!)...

In any case, I looked closely at Adam Farson, VA7OJ/AB4OJ's, detailed test of the ANAN 8000DLE, last summer...

Here are the transmit IMD test results that he published (at 14.1mhz):
-33 / -40 / -54 / -60  (with NO pre-distortion) at 200 watts
-67 / -70 / -70 / -70  (with pre-distortion) at 200 watts

FYI, the ARRL testers had some difficulty getting the pre-distortion to work well, and they found only 3db to 5db improvement in transmit IMD with it turned on, versus off....
The ARRL updated their review of the ANAN-8000DLE, stating that after their original IMD tests, they sent their unit to Apache Labs service center / Doug Wigley, W5WC (in Arkansas), where Doug quickly determined that the RF Coupler output was too high and caused the "pure signal" pre-distortion to become overloaded and seriously effected its functionality because of this overload distortion...
He changed some resistor values, which solved the problem!  (and Apache Labs has also changed these in production models)
He returned this unit to ARRL and they (ARRL) re-did their transmit IND tests and in Nov 2018 issue of QST, published the updated / corrected IMD test results of the ANAN-8000DLE...see pages 63 and 64...



John,  KA4WJA

The ARRL updated their review of the ANAN-8000DLE, stating that after their original IMD tests, they sent their unit to Apache Labs service center / Doug Wigley, W5WC (in Arkansas), where Doug quickly determined that the RF Coupler output was too high and caused the "pure signal" pre-distortion to become overloaded and seriously effected its functionality because of this overload distortion...
He changed some resistor values, which solved the problem! (and Apache Labs has also changed these in production models)

He returned this unit to ARRL and they (ARRL) re-did their transmit IND tests and in Nov 2018 issue of QST, published the updated / corrected IMD test results of the ANAN-8000DLE...see pages 63 and 64...


Here are their results (at 200 watts PEP):

(http://i65.tinypic.com/2n73vgm.png)


Comparing Adam Farson, VA7OJ/AB4OJ's tests with the new ARRL tests...

ARRL Tests (typical)
-30 / -38 / -47 / -54  (with NO pre-distortion) at 200 watts
-32 / -43 / -54 / -59  (with pre-distortion) at 200 watts, old/defective results
-54 / -64 / -60 / -60  (with pre-distortion) at 200 watts, Updated Results (from 20m for comparison to Adam Farson, VA7OJ/AB4OJ's tests on 20m, but check out the 40m and 80m results which are really nice!)

Adam Farson, VA7OJ/AB4OJ's tests on 20m:
-33 / -40 / -54 / -60  (with NO pre-distortion) at 200 watts
-67 / -70 / -70 / -70  (with pre-distortion) at 200 watts

Comparing Adam Farson, VA7OJ/AB4OJ's tests with the ARRL tests (both their original results and their updated test results)...clearly shows that pre-distortion does work....BUT...

But, in my opinion, this also shows that this is not an "off-the-shelf" / mass-producable feature...yet!!
And, is also shows (again, in my opinion) why Flex and Icom have decided to not incorporate pre-distortion into their units (nothing like marketing a feature, that doesn't work out-of-the-box, to ruin your reputation)...

Just wanted to update / clarify these results for all... :)


Fair winds...
73,
John,  KA4WJA


Title: RE: Ham Xcvrs' and Amps', Transmit Spectral Purity, IMD Products, vs. comm/maritime
Post by: VK6HP on October 15, 2018, 06:40:47 PM
John

I saw the QST update and concluded that there's a part of the ANAN pre-distortion implementation story missing and, while it could be said to be no-one's business but their own, it does impact the path to conclusions such as the one you've drawn.  For example, if the problem originated in simple manufacturing variations of the coupler, and if the production line testing was inadequate, that's a fixable situation, especially by (e.g.) large Japanese manufacturers.  On the other hand, if the parameter sensitivity in implementing the technique is so high that it's impossible for the average amateur to set up, that's a different story.  

I don't own an ANAN but am hanging out for a new exciter with pre-distortion capability to drive my KPA1500 (which has the coupler built in). Based on my investigation to date, and my reading of the ANAN-related material, I think the predistortion implementation is tractably simple to set up.  However, it looks as though there might be a case for more robust level (and perhaps other) parameter monitoring.  In saying that, I'm aware that there's a swag of people who have trouble with even proper mic gain and compressor settings via ALC monitoring but I guess it's interesting to ask if, in overall transmitter output terms, poor pre-distortion is any worse than none at all.  On the basis of the ARRL experience, apparently not.  But I'd still be wanting to take a close look at the wideband output before coming to that conclusion. It might be also worth bearing in mind that that the level issue was presumably not a gross maladjustment, and extrapolations from that situation are undoubtedly dangerous.

Pre-distortion in a radio with knobs is a deal maker for me, and I'd personally be delighted if ICOM implemented it tomorrow. Meanwhile, the 32S-3 keeps its best IMD ranking in my modest shack. I just keep reminding people of that because, 50 years after the Collins was built, it does not seem unreasonable to demand a mainstream amateur transmitter with better IMD performance.

73, Peter.

 



Title: RE: Ham Xcvrs' and Amps', Transmit Spectral Purity, IMD Products, vs. comm/maritime
Post by: G3RZP on October 16, 2018, 12:24:53 AM
One cannot get around the fact that the last generation of tube PA transceivers (using the 6146 family) were significantly better on IMD, especially the higher orders (which cause more splatter QRM), than the solid state rigs that followed them.

Not that this should be surprise when you consider the transfer characteristics of the solid state devices. It is however somewhat interesting that no manufacturer of amateur equipment ever went down the route of Cartesian feedback, which was used in VHF land mobile equipment.


Title: RE: Ham Xcvrs' and Amps', Transmit Spectral Purity, IMD Products, vs. comm/maritime
Post by: KA4WJA on October 16, 2018, 05:09:38 AM
Peter,
I had similar thoughts when I read the original ARRL test reports earlier this year (after seeing Adam's excellent results last year)...
And while I don't have an ANAN either (nor any SDR rig), when I then saw one Youtube video of an ANAN rig and its set-up, and its band-by-band "gain" settings, etc. (that were not explained well) I became concerned that there must be some "art" to actually setting-up the pre-distortion?

And, now with the updated ARRL tests and their explanation of needing the rig modified by the ANAN service center, I'm left wondering if (as you questioned) there are in fact two issues at work here??

Perhaps the user settings are easy to do?? and/or not critical??  But, when combined with a production error / QC issue from the factory, it can be a problem??

Or, is there in fact critical user settings that need more precise adjustments than we are led to believe and/or some critical hardware values that need to be better understood by the manufacturer so that they can actually mass-produce a quality product (or perhaps better final assembly / testing / adjustments... i.e. "Quality Control")??

I don't know the answer to these questions, but the real issue here, in my opinion, is:
In order for this rig (or any well-performing pre-distortion-equipped SDR) to become a major-seller in the market (such as the IC-7300 is becoming), it simply cannot have these issues out-of-the-box...
{and, I do hope Apache Labs is reading this, and addresses these issues/concerns!}
Again, that's just my opinion... :)
 
John

I saw the QST update and concluded that there's a part of the ANAN pre-distortion implementation story missing and, while it could be said to be no-one's business but their own, it does impact the path to conclusions such as the one you've drawn.  For example, if the problem originated in simple manufacturing variations of the coupler, and if the production line testing was inadequate, that's a fixable situation, especially by (e.g.) large Japanese manufacturers.  On the other hand, if the parameter sensitivity in implementing the technique is so high that it's impossible for the average amateur to set up, that's a different story.
 





If Icom could actually implement a workable, off-the-shelf, pre-distortion system, that would be great!!
And, yes, I'd be looking to buy a well-performing pre-distortion-equipped SDR with knobs, too!! :)

But, in my brief talks with Flex (last year) and my readings on the ANAN, as well as my understanding of Icom (from years of dealing with them in the maritime industry), I'm not holding my breath... :)

Maybe we  will see a rig that you and I will quickly spend our $$$$ on, in 2019?? Maybe in 2020??
There are some small / niche manufacturers working on them, but I suspect (just my opinion) it will be Flex or Icom that will be first?
 
I don't own an ANAN but am hanging out for a new exciter with pre-distortion capability to drive my KPA1500 (which has the coupler built in). Based on my investigation to date, and my reading of the ANAN-related material, I think the predistortion implementation is tractably simple to set up.  However, it looks as though there might be a case for more robust level (and perhaps other) parameter monitoring.  In saying that, I'm aware that there's a swag of people who have trouble with even proper mic gain and compressor settings via ALC monitoring but I guess it's interesting to ask if, in overall transmitter output terms, poor pre-distortion is any worse than none at all.  On the basis of the ARRL experience, apparently not.  But I'd still be wanting to take a close look at the wideband output before coming to that conclusion. It might be also worth bearing in mind that that the level issue was presumably not a gross maladjustment, and extrapolations from that situation are undoubtedly dangerous.





Peter, when I read this sentence of yours: "I just keep reminding people of that because, 50 years after the Collins was built, it does not seem unreasonable to demand a mainstream amateur transmitter with better IMD performance.", I smiled wide!!
Because, this was one of the main reasons I started this thread / quest a few years ago!
Pre-distortion in a radio with knobs is a deal maker for me, and I'd personally be delighted if ICOM implemented it tomorrow. Meanwhile, the 32S-3 keeps its best IMD ranking in my modest shack. I just keep reminding people of that because, 50 years after the Collins was built, it does not seem unreasonable to demand a mainstream amateur transmitter with better IMD performance.

73, Peter.
60 years since the 32S-3 came to the market, and 40 some years since the first mass-produced SSPA HF ham rigs, and we have gone backwards in regards to transmit cleanliness!!  And, this is during the time that "everyone" is drooling over the prospect of "100db dynamic range receivers"??
With few hams willing to stand up and say that "the emperor has no clothes" (you cannot use a "100 db receiver", because our transmitters suck!!!) We got what we asked for... :(

If some read the words of the same folks that worked so hard to bring us improved receivers...(NC0B, W8JI, W3LR, etc.)
https://www.eham.net/ehamforum/smf/index.php/topic,97093.msg1053647.html#msg1053647
And, then we all actually demand cleaner transmitters, maybe we will actually be able to use some of the capabilities of all those modern/expensive receivers??

But, as I wrote right up front...back in February:
I suppose that since most never hear themselves on-the-air, and darn few ever hear what their own transmitter does on freqs +/- a few khz (or worse +/- 10 to 20khz), the actual transmit IMD and spectral purity of our signals tend to get over-looked...and that is a shame!
So, we got what most asked for...just that most didn't know any better... :(


73,
John,  KA4WJA
 


Title: RE: Ham Xcvrs' and Amps', Transmit Spectral Purity, IMD Products, vs. comm/maritime
Post by: KA4WJA on October 16, 2018, 05:50:19 AM
Ironically, as I was composing this message I received the Nov issue of QST, and read the updated tests of the ANAN-8000DLE....
So, even if this might seem to be a digression, I do want to post this as well...
Here goes..

~~~~~~~~~


Recently, in another thread I mentioned the "ease" and "inexpense" of actually producing a "clean" HF transceiver....and I didn't want anyone to get the idea that I believe the average ham can grab some misc parts out of their junk box and in a few hours have a clean 100-watt HF SSPA...

Further, I wanted everyone to be clear that while availability of more affordable test equipment has made it capable for more hams to do some more testing, it isn't as easy as it sounds, especially when dealing with many modern HF ham transceivers which have significantly worse real-world IMD results than a two-tone test shows, due to ALC issues, etc...

How to do that, and not start arguments?   I figured maybe I should just quote someone else?  So....

About a dozen years ago, when discussing transmitter linearity testing, SM5BSZ looked at several modern amateur HF rigs (and I though some of his thoughts/results might be interesting to some here....and his words might be easier to grasp than my ramblings?? So, I'm going to quote some of this paper below).

For clarification, in these quotes (when looking at static two-tone testing, as well as discussing 2-tone versus voice testing procedures), he was referring to the transmit IMD of the legacy FT-1000D transceiver, and the ALC issues of the IC-706 series as well as the FT-1000D, and other high-end transceivers:

Quote
"This particular interference [in the FT-1000D] is generated by the cross-over distortion in the power amplifier and/or driver stages as will be shown below. The purpose of transmitter testing is to find the weak spots of each transmitter and to characterize them, so that users can minimize the problems and manufacturers will be able to improve the equipment."
  (from SM5BSZ, in 2004)

[SM5BSZ, in regards to testing]
Quote
"In SSB mode the important information comes from the peak hold spectra, because the average power spectra are difficult to obtain in SSB mode on a sweeping analyser. It is not so easy to keep producing the worst splatter level by voice for the long time of a single sweep at a video bandwidth of 30 Hz."


And, when generically discussing our poor performing amateur transmitters and their ALC issues, and testing procedures, SM5BSZ wrote:

Quote
[Other than the poor PA designs] "One of the main problems in modern transmitters is the ALC, a servo system that is designed to keep the output power below a certain threshold. Any servo system can have stability problems and the ALC system of a transmitter is no exception. The interference generated can be horrible – but a standardized two-tone test will not show anything at all. It is becoming well known that the simple two-tone test does not reveal much of the real performance of a SSB transmitter. With two constant tones that are separated by 1 kHz, exactly the same maximum power is reached 1000 times each second. With the fast attack, slow release ALC characteristic of a typical SSB transceiver, the ALC control voltage will be very close to a DC voltage with just a small saw-tooth like component superimposed on it. Likewise the power supplies will be operating under nearly constant load, and their dynamic regulation is not being tested at all. Consequently the two-tone test will not show many of the problems that may occur during normal usage with voice modulation. It only shows the fundamental linearity of the final amplifier, not the rig as a whole.

Using ALC to provide voice compression on SSB is a bad habit from old times. It was not a good idea back then and it is really stupid in modern equipment. The ALC causes a lot of terrible splatter for no good reason at all. I have been told that amateurs want to watch the ALC meter to be sure the rig operates at full power. It would be much better to remove the control function and instead detect the drive level and show that on the meter."
{BTW, there are "mods" posted on the internet that take a well-performing ALC design that is not used as a voce compressor / does not adversely effect the transmitter's IMD products at all, and turns it into a splatter-producing ALC, in order to "give your rig more audio 'punch'!"..???  There is one fairly easy mod (just changing some cap values) from a European ham, for the Drake TR-7 that does just this...so, while there are some SS HF rigs that don't ALC issues, unfortunately there are hams that create these issues themselves...}



Also, from 2004:
Quote
"If the linearity of the power amplifiers is typically good enough. The results obtained in two-tone tests do not correlate at all with the splatter generated. The intermodulation products are typically far below the ALC sidebands with real voice signals. In a two-tone test, the peak power is reached with a repetition rate of about 1 kHz, causing the saw-tooth waveform of the ALC to have a frequency of 1 kHz with very low amplitude. Therefore the two-tone test essentially shows the power amplifier linearity. But testing with a real voice into the microphone shows what signals other band users really will have to cope with – and that is often something quite different and much worse.

The simple test, just measure the emitted spectrum while modulating the transmitter as if it was on the air, has a practical problem: professional spectrum analysers are not good enough! The sideband noise levels of the oscillators in the spectrum analyser (a multiple-conversion superhet) need to be substantially lower than those in the transmitter under test, or else you are measuring the test equipment, not the transmitter. The ones I have access to have sideband noise levels of about –100 dBc/Hz at 20 kHz, and the best performance I know of in a commercial instrument is –125 dBc/Hz at a frequency separation of 10 kHz (Rohde & Schwarz FSU series). This problem arises from the need to make professional test equipment broadband from near-DC to perhaps several GHz; but for testing amateur equipment we do not need broadband coverage, and therefore high-quality measurements are not so difficult, as will be shown below.

There is another problem, however, a more fundamental one that requires some discussion. The interference caused by a transmitter, be it noise sidebands, splatter or keying clicks, occupies a large bandwidth. The level one will see on a spectrum analyser depends strongly on the bandwidth, the sweep speed and the detector used. To produce a good characterisation of the interference it will be necessary to make two measurements – one that uses a peak-hold detector in SSB bandwidth and another that uses a detector for the average power in a narrow bandwidth. The two measurements are discussed in detail below."


And further in regard to testing procedures, SM5BSZ wrote:
Quote
"Testing transmitters is a far more complicated task than testing receivers. It is complicated in the sense that it is very difficult to set up a standardised test that has a chance to be generally accepted, and that would be relevant as a figure of merit for the spectral purity of a modulated transmitter.

Personally I think that excessive high order intermodulation is a direct consequence of the standardised two-tone test, because of the unbalanced emphasis that it gives to the lower (3rd and 5th) orders. The relatively low level of the third order intermodulation visible in the standardised two-tone test may well be a consequence of design engineers tweaking the bias current of the PA and perhaps the driver stages for optimum 3rd and 5th order performance, without regard to any other consequences. The normal 3rd order intermodulation can be described as loss of gain at maximum power, as the envelope is flattened slightly at the maximum power. By deliberately setting too low a bias current to create a loss of gain at the zero crossings as well, one can add another 3rd order intermodulation component that is in antiphase and thus reduces the total 3rd order intermodulation. Such techniques are well known, and often used to take advantage of rigid type acceptance test protocols – but the adverse consequences for wideband splatter are visible as increased levels of higher order intermodulation, even in the standard two-tone test. If the FT1000D had been designed to produce good results in the peak hold spectrum, the bias current would have been just a little higher. The third order intermodulation in the two-tone test would have been a little higher too, but the higher order components would have been much lower... and that is what matters most to other band users. I have been told that the FT1000D is known to produce very clean SSB signals on the bands – “one of the best rigs”. Knowing about the cross-over distortion, amplifier noise and ALC modulation from which it suffers, and how easy it could have been to eliminate all these problems at the development stage, the conclusion is that the current state of the art in amateur radio transmitters is highly unsatisfactory. Bad design is not limited to careless keying."



Again, I just wanted to be clear that while I stand behind my words that it isn't too expensive for most radio manufacturers to do (probably < $50 - $100, extra) nor is it too difficult (as many of these engineering departments already have these designs in their files, and some have 'em in production, and/or at least these RF engineers should already understand the intricacies of designing/building a clean SS PA!), making a clean 100-watt, 12vdc SSPA ham transceiver, isn't as simple as breadboarding a few parts together and isn't going to be done by the average ham in an evening... :)

Nor is the average ham able to adequately test the actual real-world transmit IMD of their rig...

So, we rely on the manufactures to produce good, clean transmitters with fairly linear PA's and without ALC issues (which for the most part, they fail to do)...
And, many of us rely on the ARRL to actually test these rigs and hold the manufacturers feet to the fire (which for the most part, they also fail to do)...

So, while cranking up the mic gain (and pegging out the ALC) usually produces some seriously crappy signals (wide and with quite high IMD products), many of our modern rigs are just not very good in the transmit spectral purity department (poor IMD) even when operated properly....and some that are "assumed" to be great (such as the Yaesu rigs when operated in Class A) are in reality pretty crappy with even a slight amount of ALC / when set as proscribed by the manufacturer!

So, if we do desire cleaner transmitters and less interference on-the-air....and desire to actually be able to use some of the great capabilities of our receivers...well then, it is up to us (my fellow hams) to do a few things:

a)  vote with our wallets and not buy rigs that have poor transmit IMD and/or have wide SSB occupied bandwidths....and only buy rigs that have good transmit IMD and fairly narrow SSB occupied bandwidths..

b)  try to teach our fellow hams about transmit IMD, and why it is important, even if we don't have a "perfect" way to test, the ARRL two-tone tests can be used to compare...

c)  teach our fellow hams how to better use/operate their radios to improve the transmit signal and interfere less with others...even if they bought a rig that tests well, it is up to the operator to understand how to actually use the radio properly (even if that means NOT following the manufacturers' recommendations)..


Hope this helps some.
Of course, none of this is a matter of life-n-death, but certainly important for many SSB operators!

73,
John,  KA4WJA



Title: RE: Ham Xcvrs' and Amps', Transmit Spectral Purity, IMD Products, vs. comm/maritime
Post by: G3RZP on October 16, 2018, 08:24:12 AM
John,

ALC issues have been with us for many years. I still haven't managed to fix the power overshoot on my FT102 because Yaesu insisted on using ALC for power control. However, I can honestly hold my hand up and say that I NEVER put ALC into any of my professional designs! Admittedly, for maritime use when we had to have compatible AM or reduced carrier SSB (-16dB rel PEP), ALC would be a major PITA, so it was easier not to have it at all.....a VOGAD (long release time constant AF compressor) is another  matter.


Title: RE: Ham Xcvrs' and Amps', Transmit Spectral Purity, IMD Products, vs. comm/maritime
Post by: I4LEC on October 17, 2018, 07:27:29 AM
As a PowerSDR mRX PS user, the Open Software that implements the so called Pure Signal (PS) feature (aka pre-distortion), I would like to bring up my experience.

PowerSDR mRX PS and its PS built in feature can be used in association with different hardware platforms, as long as you re-address the feedback, at a proper level, out of your PA down stream coupler back to the RX input while on transmit.

Matter of fact this is commonly performed on my Hermes board (main board for the ANAN 10, 100 series) as well as on the ANAN 200 series or even Red Pitaya, these don’t have a built in coupler, when operated W/O an Amp, the feedback is taken mostly form an internal leakage, up to the bands that provide enough leakage level.

The new ANAN series (7/8000 DLE) evidently implements a built in coupler, this way, even W/O an external one, at least the transceiver can reliably take fully advantage (on all bands) of PowerSDR mRX PS available feature.

My understanding is that on the 8000, while at full power, the built in coupler output resulted too high in level to the point that the voltage divider circuit had to be re-worked  for a proper level, according to my experience, this must have been really too high as the SW also implements an automatic attenuator up to 31dB that corrects the feedback level to the optimal one, no operation is required, once you select the PS option and allow the automatic correction, it just work.

In my layout, I placed the home made coupler, a very simple strip line designed for -45dB on 10m, at the end of the Amps chain, which consist of a 200W SS PA followed occasionally by a ceramic triode tube.

This way, even if the level difference out of the coupler is 20dB (from 10m to 160m) as the strip line is designed for the higher frequency (-45db to -65dB), the internal auto attenuator can compensate it, I just add an extra 6dB pad for a total of -51dB on 10m, a setup like this allows a range of power from 200W to 2KW, useful for both, the SS alone or paired with the tube one.

Based on my observations, the optimum feedback level resulted to be around 7dB below saturation of the input level, on 10m @200W the ATT shows 20dB and 30dB @2KW, whereas on 160m it will range from 0dB to 10dB, thus covering the expected range and always maintaining the optimal feedback.

As far as I am concern, I consider it a perfect functioning feature that I have been using it for the past four years, improved along the years in many aspects, a voltage divider on the built it 8000 coupler that required a slight mod (more attenuation), to my opinion cannot invalidate it at all. :)

73, Clay


Title: RE: Ham Xcvrs' and Amps', Transmit Spectral Purity, IMD Products, vs. comm/maritime
Post by: DL8OV on October 17, 2018, 10:38:17 AM
ALC would be a major PITA, so it was easier not to have it at all.....a VOGAD (long release time constant AF compressor) is another  matter.

Sorry Peter, please could you clarify this? I thought that a VOGAD was a good thing as it replaces the microphone gain control and enables everything from a whisper to a shout to correctly modulate the TX.

Peter DL8OV


Title: RE: Ham Xcvrs' and Amps', Transmit Spectral Purity, IMD Products, vs. comm/maritime
Post by: KA4WJA on October 17, 2018, 11:32:40 AM
Okay to both Peter and Peter....
It's always good to hear from you...both of you!  hi hi

I was going to ask a clarification as well... :)

ALC would be a major PITA, so it was easier not to have it at all.....a VOGAD (long release time constant AF compressor) is another  matter.

Sorry Peter, please could you clarify this? I thought that a VOGAD was a good thing as it replaces the microphone gain control and enables everything from a whisper to a shout to correctly modulate the TX.

Peter DL8OV

Specific to why I'm looking for clarity here is:

A while back I bought an accessory synthesized remote VFO for my Drake TR-7, but haven't used it (yet)....a Noble Radio NRV-7....and included in it is a "sound card interface", etc., and a VOGAD speech compressor .

Their description of their Speech Compressor is:

Quote
A VOGAD (Voice Operated Gain Adjusting Device) is also included for SSB operation.  This is an AGC controlled speech amplifier that keeps the audio level from the microphone relatively constant over a wide input level range and greatly increases the average talk power with little distortion.

The VOGAD (Voice Operated Gain Adjusting Device) speech compressor is adjustable from the front panel gain control.
It is basically a mic amplifier with an AGC system to increase the gain on lower input levels and
reduce the gain for higher mic input levels. This tends to keep the average microphone input level to the transmitter at a relatively constant level and provides a higher average output power
level with very low distortion. With proper setting of the compressor you should see a noticeable difference in average output power with the compressor on and off.

I assume this works well in quiet environments / when close-talking a mic, as is normal in commercial SSB comms....but, maybe not so good in today's ham shacks with background noise??
Please help me understand this a bit better...


FYI, I actually didn't give it much thought, as I never found a need for speech processing with my TR-7, but also I do have the Drake SP-7 external Speech Processor (an audio in/out unit that I believe takes mic audio in, and up-converts to 455khz, then does RF clipping/filtering then demods down to audio and inputs this to the rig...)  But, have never used it either...

So, if can comment on the VOGAD for SSB operation, that would be great....any pluses / minuses??  And, any thoughts on the late 70's technology Drake SP-7, please share as well...

Thanks.

73,
John,  KA4WJA



Title: RE: Ham Xcvrs' and Amps', Transmit Spectral Purity, IMD Products, vs. comm/maritime
Post by: KA4WJA on October 17, 2018, 12:19:46 PM
Clay,
Thank You!!
Thank you so much for posting this info!!

This is exactly what we all need to know...

I am curious though, is there some reason (other than cost $$) that a wide-band flat-response directional coupler cannot be used??
Then there would be no need to set/adjust things band-by-band, either by hand or via software...
And, this would also give the end user a more seamless path to getting the rig (and the PureSignal pre-distortion) properly set-up??

{I have a really cheap coupler in the other room that is flat (+/- .5db or better) from 1mhz thru about 1500mhz....and I used to have a few others that were even better....and I've got a Bird "sampling slug" somewhere (a -50db sample) that is as flat as any ham would need across the HF range, etc..}
 
Those hams that are "software guys" or IT professionals, etc. might not have much of a learning curve, but for those of us who come from the RF side of things, we generally prefer radios with knobs, and it's gonna take a really great "computer-controlled-rig" to get us to budge....
And, one main reason for this (aside from being entrenched old farts) is the "problems" that are so often spoken of on the air and/or on-line these days...as opposed to the good facts (like Clay write of, here) that are usually unknown except to those who join a yahoo group, or are some fanboy for a product, etc...

(You know what they say, 100 good reviews and everyone just say "oh, ok"....but one or two bad reviews and everyone says "what a piece of crap", etc...)

Clay, thanks again for posting your experiences and giving us all some much needed info on how this all works and most probably how/why the ANAN-8000 that the ARRL tested, needed to have some circuitry changes...



Finally, for everyone...
In my personal opinion, this (pre-distortion) is a great feature that we have all been discussing here for half a decade....but, the way it is working / the way it is being implemented into our ham rigs (as of today, Oct 2018...Apache Labs is the only one with a full-power, pre-distortion-enabled, HF-SDR rig), is not quite "ready for the mass market"...

Again, in my opinion, it might be "mature technology" in the lab, and/or in the hands of software guys/It pros, but in the hands of even seasoned hams, problems still exist....and it's not quite ready for prime time, so-to-speak...

Again, I love the idea....and I wish every rig made had this....and every amp had a -50db to -60db directional coupler output....and I do hope this happens soon...
But, as of today (Oct 2018) it just isn't here, yet!


Further, this whole explanation / discussion about pre-distortion shows how smart the guys at Icom (and even at Flex) are... :)
Yes, I know some of you will think I'm being sarcastic, but I'm serious....they decided to not worry about pre-distortion and concentrate on what works and what features their customers wanted, at least to some extent....

But, it also shows how really super smart the Apache Lab, and PowerSDR, guys are!!!
They are leading the way forward in amateur radio SDR....and if they can get some of the RF things sorted-out and get the bugs out of the software, they will be leading the way....well leading the way, right behind Icom... :)
'Cuz as well all know, the 800lb Gorilla will eventually be considered the leader, even if the little guy (Apache Labs) is really the fore-runner... :)


Thanks again Clay!

73,
John,  KA4WJA


Title: RE: Ham Xcvrs' and Amps', Transmit Spectral Purity, IMD Products, vs. comm/maritime
Post by: K6AER on October 17, 2018, 03:03:10 PM
IMD Specifications and this Holy Grail for the lowest IMD numbers are moot point when the ham uses the VFO and places his SSB signal 2 KHz from an adjacent QSO. Next the mic. gain knob, is a bigger offender of spectrum purity. Today's modern radios are a far cry from the once convent designs of 15 years ago. I see many older radios with products going out 4 KHz on the opposite side band.

If you want to make the phone bands more civilized just require channelization of phone frequencies to be every 5 KHz.



Title: RE: Ham Xcvrs' and Amps', Transmit Spectral Purity, IMD Products, vs. comm/maritime
Post by: I4LEC on October 18, 2018, 10:56:19 AM
John,
I am pleased it serves to clarify some things, I am obviously involved and thus these aspects are much more familiar within my environment.
Here below in red my further comments to your questions

I am curious though, is there some reason (other than cost $$) that a wide-band flat-response directional coupler cannot be used??

Not at all, is actually strongly recommended using a flat wide band one, that will be even safer in order to prevent a possible front-end failure in case of malfunction.

Then there would be no need to set/adjust things band-by-band, either by hand or via software...
And, this would also give the end user a more seamless path to getting the rig (and the PureSignal pre-distortion) properly set-up??

No need to setup anything, at least from when the auto attenuator was implemented, which is a way back (three years or so), prior to that, a manual attenuator setting was required in order to determine the proper feed-back level.

{I have a really cheap coupler in the other room that is flat (+/- .5db or better) from 1mhz thru about 1500mhz....and I used to have a few others that were even better....and I've got a Bird "sampling slug" somewhere (a -50db sample) that is as flat as any ham would need across the HF range, etc..}

Well that Bird sampling slug of yours will be just fine along with few extra dBs pad to be on the safe side when an Amp is on the line.

Again, I love the idea....and I wish every rig made had this....and every amp had a -50db to -60db directional coupler output....and I do hope this happens soon...
But, as of today (Oct 2018) it just isn't here, yet! 

John, I think you have been heard, the latest Amps, Expert, Elecraft, Flex Radio, Acom and others, do have the -60dB tap, which, in my opinion, is just a marketing feature, as you were saying, at the present time, if used for pre-distortion purposes, can only be linked to an Apache Labs radio, some of these manufacturers may don’t even know who they are!

73, Clay


Title: RE: Ham Xcvrs' and Amps', Transmit Spectral Purity, IMD Products, vs. comm/maritime
Post by: KA4WJA on October 24, 2018, 12:46:03 PM
Mike,
I've purposely not responded to some of the comments, as that might pull us off topic, and cause some that actually wish to learn, to become turned-off and move away... :(
But, I hope you won't mind me clarifying a few things, in polite and friendly way??
Mike, please understand this is not personal at all... :)


1)  Over the years you have repeatedly mentioned the mic gain control as being a (large?) part of the problem of splatter on our phone bands....and I agree with you, that this is a problem...(and I haved voiced that agreement here, many times) :)  
And, while I suspect that most here also agree that those running "all knobs to the right" are not actually educated enough to understand this discussion here, the rest of us are...
But, you seemed to have missed the main point of the discussion...

The main point of this discussion is, and has been, that even when operated as prescribed in the manual, many of our "modern" rigs are just crap compared with what used to be standard for the amateur radio service, and inferior to what is being produced for other HF services, today...
(also, that while "higher-voltage PA's" are nice, and can have better transmit IMD, the actual ham HF rigs being made/sold, are not showing much in the ways of "improved transmit IMD", and the fact that some 12vdc PA's are actually better is surprising to many, but the results are right here in this thread for all to read for themselves..)

So, we all get it....you wish everyone would crank down their mic gains....and so do I...
But, if you take the time to actually listen on-the-air (as I do) and listen to what rigs are being used (as I do), and listen to how they are being used, etc....and read what is written here, etc....you may find that there is some important info being imparted here, and that some here may actually be interested in learning... :)



2)  And, when you make mention of channelized (HF maritime, HF Fixed / Land-mobile, etc. uses 3khz channels) operation, you seem to imply that requires less stringent transmit purity?? (when in fact these services have required more stringent transmit purity, because of their historical inability to "move" away from interfering stations, although with some private users this is now done..)
But, then also state that we hams like to use tight spacing of our QSO's (which I agree we do!)....but you use 3khz as the "ham standard" (along with 2khz, in tight conditions, like contests??)
This is confusing to me...but, no worries here...
'Cuz we do agree that our ham transceivers' transmit IMD and spectral purity does need to be improved!!  And except for the above-mentioned guys who crank-up their mic gain, how we do that is, by demanding better of the manufacturers....just like we did over the past 10 - 20 years, in regard to improved receivers (both better close-in IMD and better phase-noise/RMDR)...


{As I, and others, have stated here, we are not discussing "contest operations" (where both common courtesy and common sense, seem to get ignored for the weekend)...but rather every day, normal operations....
BUT...
But, to be clear, as long as I'm not trying to dig someone out of the noise, 60db below most other stations, I have no problem if someone with a nice clean signal wants to start up 3khz away from me on the ham bands...it happens all the time!  :)
But, if they're using an IC-7600, etc....or maybe an FT-857 and a ALS-600...then I might not like it so much!!  
And, during contest times, stations 1.5khz to 2khz away are quite common....
So, further....while audio fidelity suffers when narrowing the passband much below 1.5khz to 1.8khz....I do have an SL-1000 (1.0khz) IF filter in my Drake TR-7 (along with a 1.8khz and 500hz, as well as the standard 2.3khz)....
(http://i66.tinypic.com/294owur.jpg)
And, with the TR-7's imperviousness to overload, and its > 100db of ultimate filter rejection, I can use the passband tuning, and my 1.0khz IF filter and still have a 75m QSO with my best friend (using his TS-830 w/ filters in both IF's and his VBT)....with another station 1.5khz away, just fine!  (heck, a few years back, I think that was during the Nov SS about 10 - 12 years ago, we even had stations 1khz away, and we still had good comms, 100% copy....again, not very good fidelity, but 100% copy nonetheless!!  And, since the other stations were not able to force us to move, and of course they were unable to make much of a QSO-rate, they simply move, and we can then open-up our passbands and enjoy our rag-chew...)
Sorry, for the digression....the above paragraph has nothing to do with transmit IMD....but just shows what can be done on-the-air... :) }


My first hand knowledge of US Embassy comms, stops in the mid 90's (I consulted on/off with some USAID folks, from the late 80's thru early 90's....and they were using ITT/MacKay 8000's and 1020's back then...nice rig for the day, but certainly not up to handling the crowded ham bands....but do have a few friends who someone were "given" some of the 1020 amps...Sweet! :))
So, I will defer to your apparent first hand knowledge of 21st Century US Embassy HF comms....and the IC-7800....
(but, I seem to remember that the 7800, even with its 50-volt PA, isn't much better than the 7600?  and the 7600 is a really WIDE transmitter!!  The 7800's 5th and 7th products are about 10db better than the 7600, but the 3rd, 9th, and higher orders are about the same....and this means the 7800, no matter what "filters" Icom might have put in its receiver, has a fairly poor transmitter, especially when looking at the much lower cost "12vdc PA" kenwood TS-590SG!!)

In the US the only operation of radios not channelized is ham radio. Marine, Land Mobile, Public Service, Maritime, Aviation, Military and even CB is channelized.

When the IC-7800 came out the radio was targeted for the US embassy communications which is channelized. When offered to the ham radio market they had to improve the IF filters in the 7800 for we (hams) like to operate 3 KHz away from other stations.

IMD Specifications and this Holy Grail for the lowest IMD numbers are moot point when the ham uses the VFO and places his SSB signal 2 KHz from an adjacent QSO. Next the mic. gain knob, is a bigger offender of spectrum purity. Today's modern radios are a far cry from the once convent designs of 15 years ago. I see many older radios with products going out 4 KHz on the opposite side band.

If you want to make the phone bands more civilized just require channelization of phone frequencies to be every 5 KHz.
FYI, the only way modern ship-to-ship maritime SSB Voice comms survives today on-the-air (with many sailors using ham rigs "opened-up" to transmit out-of-band) is by them using "non-standard" maritime HF freqs (away from the standard / int'l assigned HF channels)...

Example: for decades I (and many, many others) have used 12.359mhz daily for long-range, transocean HF SSB Comms (typically at 150 watts PEP)....with 12.362mhz and 12.365mhz being used as SSB Voice Weather broadcasts (at 1000 watts PEP) from shore stations, at bottom and top of the hours....and never has anyone experienced interference...
BUT...

But, fast-forward to the past two years or so....and now we have many baby-boomers retiring and 100's of them using modified ham rigs on their boats....and they have indeed caused a great deal of interference....so, in order to keep interference away from some users of the 12mhz simplex freqs (12.353, 12.356, 12.359, etc. as well as those Voice Weather broadcasts), 12.350mhz (a non-standard maritime freq) was allocated to a few HF coast stations and also authorized for use by vessels licensed under the maritime mobile service....(and this channel will be in use daily now, mostly in late afternoons, by many boats sailing across the oceans)

Further...I (and many others) used to use 8.294mhz as a secondary long-range channel (and now-a-days, with low solar activity it should be a primary HF, transocean SSB Comms channel)...but, due to the adjacent channel interference, most users have migrated to "shared"/'"secondary" HF channels...
{the FCC and ITU, allocated these "fixed/land-mobile" HF channels on a "shared" / "secondary" basis for all licensed maritime mobile stations to use, for specific purposes....again on a "shared, secondary" / "non-interference" basis.....to be clear, these addition channels were of course not allocated because of interference caused by maritime users (whether using ham rigs or commercial maritime rigs)...it was just a "happy" happenstance that as more an more hf ham rigs began to be used on-board more boats, that these "new channels" were available...however the USCG and the IMO pushed heavily for this, as to improve the situation of adjacent-channel interference....as 8.291mhz is the 8mhz GMDSS SSB int'l safety/distress calling freq...and 8.294 and 8.297 were the only other allocated 8mhz simplex freqs....}
These HF land-mobile channels (just like the primary maritime channels) are spaced 3khz...
Starting at 4.000mhz, 4.003mhz, etc....up to 4.060mhz.....and from 8.101mhz, 8.104mhz, etc....up to 8.191mhz....
FYI, the specific reasons for these new allocations were:
Quote
for supplementing ship-to-shore channels for duplex operation;
for Intership simplex (single-frequency) and cross-band operation;
for cross-band working with coast stations;
for duplex operation with coast stations working in the band 4438-4650 kHz or with Channels 834, 835, 836 and 837;
for ship-to-shore or shore-to-ship simplex operations (8100-8195 kHz only).

Mike, of course, now-a-days with maritime HF-DSC (and lower cost sat comm) there are fewer and fewer public coast stations, and as such not much traffic on the duplex / ship-to-shore channels, but in recent years there has been an uptick in simplex ship-to-ship (and simplex shore-to-ship) Voice SSB comms....and with the increase in ham rigs being used on these maritime channels, there have been quite noticeable issues...

Again, I cannot speak about modern US embassy HF comms (my personal, first-hand experience there ended in the mid-90s')....but, I can speak of our modern 21st century HF ham comms, as well as maritime HF comms (which I use almost daily) as well as HF Fixed/Land-mobile comms...


To be continued below...

73,
John,  KA4WJA


Title: RE: Ham Xcvrs' and Amps', Transmit Spectral Purity, IMD Products, vs. comm/maritime
Post by: KA4WJA on October 24, 2018, 12:58:35 PM
Continued from above....

3)  But, directly on point to what you were asking / commenting on...regarding how close do hams operate, etc....
Of course as Carl mentioned, it all depends on conditions, etc... :)
But, please have a look at what was posted here this summer....and you might just see the gist of what we have been discussing... :)
And, yes....if everyone adjusted their rigs better / turned their mic gains down a bit, we would have less splatter....but, again that is not what this whole discussion has been about....rather it is about how poor our "modern" rigs are in regards to transmit IMD even when operated properly (as most hams do)...and about what rigs (ham and maritime) are actually better than most...


...no powerpoint and no photoshop...just a couple pics from NC0B's talks (some courtesy of W6XX), etc., with some of my crude drawings to help...[Please forgive my crude drawing, and understand these drawings are not precise/absolute!]

Also, please note that I debated whether to use just the few scans using white noise, that I have, rather than try to use some two-tone scans (and draw-in the actual occupied bandwidth)??  If I use some two-tone scans and draw stuff in, some will just cry foul and some/much of all this effort will be for not....and I do not wish to run off on more tangents about transmitter testing, tone freqs, etc. etc...I just want to address Brian's legit question, asking what are the compelling reasons to improve our transmit IMD / spectral cleanliness... :)

So, I think I will just include the few white noise scans and use them as comparisons, and these are NOT meant to insult any specific radio, they're just what I have available....hope this is okay??
Now before anyone balks, and says that striving for 60db S/N (or S/interf) ratios is a ridiculous idea on our HF ham bands...no worries here, I'm not saying that is the goal!  :)   Although, it would be nice, what I'm just saying is that we can do better than what we're being sold these days, and if we can get a 10db to 20db improvement in average transmit IMD (do-able and affordable) from our HF rigs, the bands would be easier to use, and friendlier, too!  :)

{Although, in the world of commercial HF / maritime HF ~ 60db S/N is done all the time....we are not in that business, we're hams....and getting a 20db to 30db S/N on HF SSB, is good with most of us....but remember that there are many times where there are stations close in freq (even directly adjacent) that can be 30, 40, 50, 60db, or more, different in strength...heck, on some of my 75m operations, I've had a couple guys S-9 +30db (or more), and one or two only S-7 or less...and that's as much as 50db difference, in the same round-table!  and this is one reason that I give one or two of them some good-natured ribbing for not having a decent antenna and/or a nice amp (hi hi)....'cuz it's a pain to run the RF gain up to hear the S-5, S-6, or S-7 guys, when the others are 20 to 30+ over...:)  So, even if you think your transmitter isn't so bad, remember there are others on adjacent freqs that might be in QSO with signals significantly weaker, and your transmit IMD could be seriously detrimental to those guys!!}

[The final preface here is a reminder that these are not worst-case scenarios, but rather just average everyday situations....no extremely crowded conditions, nor seriously offensive transmit IMD, nor super wide variations in signal strengths...just showing average normal stuff, from average rigs...]

This first image (courtesy of W6XX, from a paper presented by Rob Sherwood), show two rigs running at 75w PEP....one is an FT-1000 MkV in Class A;  the other is a K3;

 (http://i66.tinypic.com/24w8tna.png)

The FT-1000 MkV in Class A @ 75 watts PEP, shows a nice clean (and narrow) spectrum...only 6khz wide, at -60db down!!! (that's about 1.6khz to 1.8khz from the transmitter passband)

The K3 @ 75 watts PEP, in comparison, is fairly wide...about 15khz wide, at -60db down...(that's more than +/- 6khz beyond the transmit passband)


This second image shows two different rigs, operated at 100 watts....one is a modern IC-7600;  the other is a bit older / legacy IC-756ProIII;

 (http://i65.tinypic.com/jai6fb.png)

The 756ProIII isn't too bad, but still pretty wide...14khz wide, at -60db down...(about +/- 5.5khz from xmit passband)

But, the IC-7600 is really wide...20khz wide, at -60db down...(that's about +/- 8.5khz from xmit passband)


In this third image, I took the original image of the FT-1000 MkV  vs.  the K3, and I drew in some other signals (red, yellow, and blue), and if the top line of the spectrum analyzer display (ref level) is at say S-9 +20db to S-9 +30db (considering approximations and normal HF fading), and the other signals, +3khz (yellow),  -3khz (red),  and -6khz (blue),  are of accordingly weaker strengths....

 (http://i67.tinypic.com/1eukup.png)

The "white" signals (at 14.200) =  S-9 +20db to S-9 +30db

The "yellow" signal (at 14.203) =  S-8 to S-9  (30db weaker than the "white" signals)

The "blue" signal (at 14.194) = S-8 to S-9 (30db weaker than the "white" signals)

The "red" signal (at 14.197) = S-7 to S-8 (40db weaker than the "white" signals)

If you look at how much of the various colored signals are "above" the "white" signal, you can see the approximate S/N, or S/I (Signal-to-Interference) of those QSO's....and you can certainly see how easy / difficult those QSO's will be...

The "yellow" QSO guys would need some IF shift and probably a narrow SSB filter to have an acceptable QSO when the K3 is transmitting....but not much of a problem, when the FT-1000 MkV is transmitting... :)

The "blue" QSO guys might be okay, when the K3 is transmitting...although, they'd still want to narrow their rec passband and adjust their IF shift a bit...

The "red" QSO is not going to be long-lived here....they'll likely QSY or they're done... :)

If you can increase power or antenna gain in the desired direction on some of the color QSO's (or, even better, if they can rotate their antennas to place their nulls onto the K3's signal), that can help...or get the "white" QSO guys to reduce their power, turn their antennas, etc...or any combination of these....this can all help...but....but, except for the "color" QSO guys turning their antennas to null out the k3's signal as best they can, there's little chance of these other things being done...

But....If you can narrow the occupied bandwidth of these transmitters, everyone's QSO's improve!!  Hmm....what a novel idea....let's reduce our occupied bandwidth / improve our transmitters' IMD, and everyone wins!!

If it was just someone's mic gain being cranked up to max, or serious amp over-drive, that would be an easy fix....but, you see these scans of transmitters are not with mic gains cranked all-the-way up...nope these are with the rigs operated as designed/proscribed....and these are the best they're gonna get!  :)  These are not worst-case....not even close....This is just "normal" / "everyday" operations....


If you want to see what it could be like, have a look at the 4th image...look at just the narrow "white" transmission (the FT-1000 MkV) and look at the dotted lines of the "color" transmissions...and what-do-you-know, you now have 4 different QSO's, at different signal strengths, all spaced about 3khz apart, and nobody is interfering with their neighbors...[Again, please forgive my crude drawing, and understand these drawings are not precise/absolute!]

 (http://i66.tinypic.com/1z67ma.png)

Hmmm....is this compelling??  Not sure about everyone here, but it is to me... :)


And, for those that might think Class A operation is needed, or that we need to go back to vacuum tube PA's....I highly disagree with both of these...(see earlier posts for info on what is easily possible to accomplish in solid-state Class B PA's)....

{I know some are waiting for all HF rigs to have active pre-distortion, but as of 2018, Apache Labs is the only one doing it...and with literally 100's of thousands of hams (millions) on the HF bands using analog rigs and/or DSP rigs, and only a couple thousand using SDR's, active pre-distortion is a LONG way from being ubiquitous!! A REALLY LONG WAY!!  So, maybe we hams can vote with our wallets, and demand better transmit IMD, now....not wait 'til some manufacturer decides they'll grace us with that "privilege"??   I mean it's really up yo us, the technology is there (been there for decades) and it doesn't cost a lot....it's up to us to demand it! }

Have a look here at this 5th image....which shows an FTdx-5000 in Class A operation...(FYI, this is a10khz wide image, rather than the above 20khz wide images)

 (http://i67.tinypic.com/rssya9.png)

Note the vast difference in the occupied bandwidth between having 1/2-scale of ALC, versus No ALC at all....

1/2-scale ALC = it's almost 11khz wide at -60db down...better than any of our "modern" rigs that have Class B SS PA's, but not what most think of as that wonderful Class A advantage..(that's because of Yaesu's ALC)

No ALC = it's only 5.8khz wide at -60db down!!!  (just about 1.6mhz from xmit passband, it's 60db down!)  And, that is very nice!!


Finally #4  (yeah, there was supposed to be only 3!)

#4 -  While I was writing all the above, it dawned on me that I probably should include a few other comments regarding a "compelling reason" to improve our transmit IMD...but some of these final points are opinion, rather than the many facts above...so, wasn't sure whether to write these or not, but here goes:

--- It makes good sense.

--- It's efficient use of the airwaves.

--- It is the polite / courteous thing to do.

--- And, that it meets 4 of the 5 basic reasons/tenants for the existence of the amateur radio service.

After all, from Part 97, the 5 basic reasons / purposes of the Amateur Radio Service are:

"The rules and regulations in this part are designed to provide an amateur radio service having a fundamental purpose as expressed in the following principles:

(a) Recognition and enhancement of the value of the amateur service to the public as a voluntary noncommercial communication service, particularly with respect to providing emergency communications.

(b) Continuation and extension of the amateur's proven ability to contribute to the advancement of the radio art.

(c) Encouragement and improvement of the amateur service through rules which provide for advancing skills in both the communication and technical phases of the art.

(d) Expansion of the existing reservoir within the amateur radio service of trained operators, technicians, and electronics experts.

(e) Continuation and extension of the amateur's unique ability to enhance international goodwill."

--- So, to advance the radio art, advance the skills in both the communications and technical phases of the art, expand the reservoir of technicians and electronic experts, and enhance international goodwill....4 of the 5 purposes above...having a clean transmitter and allowing others to use the airwaves without adverse interference, and learning about how this is done, etc., actually does accomplish 4 of the 5 of these....so...

--- How about we look at what we are trying to accomplish here...inform and educate our fellow hams, regarding reduction of on-air transmit interference (and hence allow those who bought "90db to 100db dynamic range radios", to actually get close to being able to use some of that potential).


I do hope this here, and all the rest of this thread (please read it), gives some of you compelling reasons to improve our ham rigs' transmit IMD, improve our transmit spectral purity...if not, that's okay....not going to go off on a rant, nor engage in any arguments, so I will just agree to disagree, politely.  :)

Fair winds and 73,

John,  KA4WJA


So...
So, aside from the guy with "all knobs to the right", who would rather operate next to??

?? Some guys with modern rigs like the K3 / K3s, the IC-7600??  Or even a FTdx-5000 adjusted as the manual prescribes (w/ ALC)??

??  Or some with IC-756ProIII or FT-1000MkV (in Class A)???  (or maybe even a nice Icom M-802, or JST-245, or TR-7, IC-781, etc.??)

?? Or maybe some with ANAN-8000's w/ "pre-distortion" on??

??  Or, if you want to look at tube rigs....how about guys with TS-830's or Collins 32S-3's??

Again, aside  from the guy with "all knobs to the right", who would rather operate next to??
The facts are there for you to read and look at....
The choice is yours...
Who do you want to operate next to??  
And, how wide of a signal do you want to transmit??  How much on-air pollution do you choose to transmit??

Do, we hams want to learn / educate ourselves??
Do we want to use our wallets and "demand" manufacturers make better transmitters??

The choice is ours....
If some here wish to dismiss this as a "non-issue", that is their choice, and I will not argue with them...
But, to imply that we hams are "too demanding"??  That, in my opinion is just sour-grapes BS!!

We used to have much cleaner transmitters....we used to have much worse receivers, too...
We "demanded" better receivers and we got 'em...

What if the 1000's upon 1000's of hams clamoring for better receivers actually read what Rob Sherwood (and many others) have been saying for years (instead of just looking at some list)....if they understood what he (and many others, myself included) have been writing for many years now??  

That it is out TRANMITTERS that are the limiting factors of our RECEIVERS now..
What do think could happen??

Could we end up with 10's of thousands of hams actually willing to spend an extra $25 to $50 for a rig with a clean transmitter??
Goodness, what are the odds that that would happen??
That someone would actually sell a product that the consumer wanted?  Is that possible now-a-days, or are all consumers now just sheep being led to the trough and being fed whatever some designer and marketing guy tells them they "need"
 (like Apple / Steve Jobs, and the iPhone, etc....don't get me wrong, Steve Jobs was a genius!!  Just that he had a knack for convincing folks that they "needed" something that they didn't even understand....pure genius! :) )
 


What's that old saying?
"With hard work, much is accomplished....but, with faith, All is possible!"


I choose to have faith in my fellow hams...


73,
John,  KA4WJA


Title: RE: Ham Xcvrs' and Amps', Transmit Spectral Purity, IMD Products, vs. comm/maritime
Post by: KM1H on October 24, 2018, 03:00:30 PM
Back in early August a long time ham friend was well into Alzheimers and his wife wanted me to get his ham gear ready to sell or give to a son in DE who was also a ham.

He had messed up the IC-7800 he had bought new and rather spend considerable time learning this beast I sent it to Icom-Michigan.

When it came back I put it on the bench, turned on the SA and just made some basic "Hola Radio" tests. The IMD from 3 to forever was far from spectacular and went from ~ -32 3rd real dB in a steady progression down to ~ -60 dB.  Nothing scientific as I was just curious as to what a $12K radio would do.  My slightly modified TS-940 run at 80W and stock TS-950SD at 100W both started about 10 dB better and had a slightly slower curve to -60 which was a bit further out. Those power levels were the best sweet spots.

The 7800 had much lower TX noise with no drive than the 940 while the 950SD was only slightly worse. Both KWs are mid to late 80's designs with the 950 their flagship model.
I didnt bother lugging over a TS-830 as I knew Id be highly pissed off...been there done that with several brands of rice boxes plus TT crap.

My 1959 CE-100V phasing rig with USA Tung Sol 6550's is also in the superb class.

Carl


Title: RE: Ham Xcvrs' and Amps', Transmit Spectral Purity, IMD Products, vs. comm/maritime
Post by: KA4WJA on December 03, 2018, 10:42:20 AM
Just a brief update / anecdote...and a reminder (to me as well) that we cannot "hear" splatter / poor transmit IMD "on-freq"...
Of course if it's really bad there are usually corresponding distortions in the transmit audio, this is not always the case, and most importantly the lack of audible distortion "on-freq" cannot be used as an indicator of a "clean" transmit signal... :)

This past month, operating on the maritime HF bands I heard a friend (a seasoned ham and long-time maritime op as well) with a weird audio problem, he was operating a private maritime coast station and as such was of course required to use only FCC Part 80 type certified transmitter, so I was concerned that he had a problem that he was not aware of....(he had a somewhat harsh sounding audio and a rather abrupt sound on the end of some words and at end of transmissions, not actually distorted but sounded overdriven?)

My first thought was maybe he's got some RFI or RF feedback into his rig?  Or maybe he added something? (a new mic, or an external amp that is causing problems?)

Being on 12mhz, late afternoon, about 1000 mile path, his signal was strong (S-8 to S-9+), and I have low noise level so S/N was excellent!  But he had this weird audio issue....so, as he was in comms with another station I tuned up and down to check his spectral purity, transmit IMD, splatter, etc....and as I tuned up and down, I found nothing!  No splatter, no spurts nor sputters....(3khz away was clean and silent!)
And, as I tuned up/down further, I still found no issues!  
Everyone else's signals on this Net were also good as well, with no issues heard anywhere off-freq from 3khz out to +/- 15khz...(but, did hear two other coast stations from Australia, 9000 - 11,000 miles away, with clean signals too!)

So, I assumed he had some audio issue...
And, brought this to his attention (on-the-air and followed-up in email)....he found and fixed the problem!
 
Turns out he was running an Icom M-802 maritime rig remotely, via an IP connection....and it was his computer mic / audio that was a bit harsh and overdriven....not sure if he found the input to his computer or the output to the rig to be where the overdrive was causing the most of the problem, but he found both to be issues....and corrected them.

A couple weeks later, I was on-the-air with him and all was good!  :)

I just wanted to write this so everyone can see that even those that should know better occasionally have issues that they caused themselves and it takes someone on the air to notice and help 'em out....and also wanted to remind myself that just 'cuz I hear a crappy signal, that doesn't mean they're splattering, nor vice-versa that just 'cuz I hear nice clear audio, that dosen't mean he isn't splattering!!   :)


Fair winds and 73,

John,  KA4WJA

  


Title: RE: Ham Xcvrs' and Amps', Transmit Spectral Purity, IMD Products, vs. comm/maritime
Post by: AE0Q on December 03, 2018, 08:10:53 PM
A question for John,  KA4WJA (or anyone else, I guess)..

How do the modifications made to transmitters for ESSB (notably by Voodoo Labs) relate to signal bandwidth and purity ?

Glenn AE0Q


Title: RE: Ham Xcvrs' and Amps', Transmit Spectral Purity, IMD Products, vs. comm/maritime
Post by: KA4WJA on December 04, 2018, 07:45:52 AM
Glenn,
First off, I have no knowledge of "Voodoo Labs"...

But, secondly, as for ESSB (Enhanced SSB) where increases in low-freq audio response, and wider audio and RF bandwidths are designed/encouraged, this is (in general) a very bad idea for both transmitter bandwidth and spectral purity...
A question for John,  KA4WJA (or anyone else, I guess)..

How do the modifications made to transmitters for ESSB (notably by Voodoo Labs) relate to signal bandwidth and purity ?

Glenn AE0Q

Glenn, in general:

a)  the enhancement of (or even the flattening of) the standard audio passband of an SSB transmitter, results in higher levels of lower and higher freq audio, there by increasing the levels of IMD products...

b)  the increase in bandwidth, increases the spacing / width of the various audio tones of speech, thereby spreading the resulting IMD products out farther/wider....

c)  the increase of the low freq response, has an even further detrimental effect....in that opposite sideband emissions are worsened (as can be carrier suppression and carrier noise)

d)  of course, just the fact that you're making the signal wider in the first place means that it is wider!!  (and, of course those ESSB guys always use only this one point to make their argument....usually saying that they're narrower than the AM guys...but if you point out the 3 main issues above, they are left looking fairly ignorant...)

e)  and, while this point is more radio-specific...fact is that these wider, and higher level higher/lower audio tones, can drive the succeeding stages of the rig into further non-linearity...AND also can further tax the rigs PA and power supply, even further exasperating the situation....




Opinion alert:
The "enhancements" they are doing, are, in my opinion, certainly 180 degrees away from "good engineering" and "good amateur practice"...and if you add in the fact that some of these ESSB guys are  using rigs that don't have decent transmit IMD to start with, it starts to look pretty bad in regards to intelligence / knowledge of these operators... :(
But, as I write, this is just my opinion...


Hope this helps answer your questions??

73,
John,  KA4WJA



BTW, I still think the Alpha 77x series were the best amateur HF amps built (I know some will say Henry Radio's were better, but unless you get to the big 3k, 4k, 5k, 8k, console amps, nothing compared to a Alpha 77 as a desktop amp)...I love my 77Sx, it's > 35 yrs old, with original Eimac tubes....very clean in the IMD area, stable as a rock, high-gain, easy to tune, runs all day long (Brick-on-the-Key, etc.)
And I can't figure out why anyone making amps these days wouldn't consider making such a model?
No need for auto-tune, nor "protection circuits", etc.. :)



Title: RE: Ham Xcvrs' and Amps', Transmit Spectral Purity, IMD Products, vs. comm/maritime
Post by: KA4WJA on April 17, 2019, 10:43:35 AM
Yeah, it's been a few months, there is not much new to add...and I'm sure some will not be too happy about resurrecting this thread (but it is almost Easter).

But, with all the recent talk of amps for FT-8, amps for some particular rig, etc...and those looking for reasonably-priced amp, etc...
I thought this might be useful for some to read...especially as I see some folks mixing up "harmonics" and "IMD" these days...

If you can't wade thru the whole thread (even I can no longer do that!), have a look at page 8 and page 18...(see links)

https://www.eham.net/ehamforum/smf/index.php/topic,97093.105.html

https://www.eham.net/ehamforum/smf/index.php/topic,97093.255.html


73,
John,  KA4WJA