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Author Topic: Ham Xcvrs' and Amps', Transmit Spectral Purity, IMD Products, vs. comm/maritime  (Read 154030 times)
KA4WJA
Member

Posts: 1098




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« Reply #255 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.  Smiley

Brian - K6BRN

It exceeds the eham maximum length!
So, I will edit / break it up...

73,
John,  KA4WJA
« Last Edit: July 11, 2018, 05:09:39 AM by KA4WJA » Logged
KA4WJA
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Posts: 1098




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« Reply #256 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!  Smiley   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!  Smiley

{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...Smiley  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.  Smiley

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.  Smiley
     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. [Huh 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? Smiley )

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!  Smiley  {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
« Last Edit: July 11, 2018, 05:12:32 AM by KA4WJA » Logged
KA4WJA
Member

Posts: 1098




Ignore
« Reply #257 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!  Sad

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! Smiley

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!  Smiley

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
« Last Edit: July 11, 2018, 05:16:06 AM by KA4WJA » Logged
KA4WJA
Member

Posts: 1098




Ignore
« Reply #258 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... Smiley

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!  Smiley   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!  Smiley

{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...Smiley  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;

 

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;

 

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....

 

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... Smiley

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... Smiley

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!  Smiley  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!]

 

Hmmm....is this compelling??  Not sure about everyone here, but it is to me... Smiley


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)

 

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.  Smiley

Fair winds and 73,

John,  KA4WJA
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KM1H
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« Reply #259 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
« Last Edit: July 11, 2018, 06:57:28 AM by KM1H » Logged
KA4WJA
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« Reply #260 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
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« Reply #261 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

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KA4WJA
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« Reply #262 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

« Last Edit: July 11, 2018, 01:33:02 PM by KA4WJA » Logged
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« Reply #263 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 Roll Eyes Grin  We visited last year.

Carl
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HAMHOCK75
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« Reply #264 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?
« Last Edit: July 12, 2018, 07:56:53 PM by HAMHOCK75 » Logged
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« Reply #265 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
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KA4WJA
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« Reply #266 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
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SWLER1965
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« Reply #267 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
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« Reply #268 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.
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KA4WJA
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« Reply #269 on: September 25, 2018, 11:16:41 AM »

Jon,
I'm glad you found this helpful... Smiley

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!!  Smiley}


{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... Smiley


~~~~~~~~~~~


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!!!  Sad


73,
John,  KA4WJA
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