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Author Topic: Ham Xcvrs' and Amps', Transmit Spectral Purity, IMD Products, vs. comm/maritime  (Read 154149 times)
G0HZU
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Posts: 163




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« Reply #225 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... Smiley

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 Wink
« Last Edit: April 18, 2018, 02:23:50 PM by G0HZU » Logged
KB2TIS
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Posts: 18




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« Reply #226 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?
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G0HZU
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Posts: 163




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« Reply #227 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.
« Last Edit: April 18, 2018, 04:09:53 PM by G0HZU » Logged
G0HZU
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Posts: 163




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« Reply #228 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.


« Last Edit: April 18, 2018, 06:43:34 PM by G0HZU » Logged
KA4WJA
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Posts: 1098




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« Reply #229 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.  Smiley  
(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. Sad

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. Smiley Thanks!

{If you actually read this thread, you would already understand all the above. Smiley }


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):




Here is the M-802 (on 16mhz), showing to -80db(PEP):




Here is the Collins 32S-3, showing to -80db(PEP):




Here is the Icom IC-781, showing to -80db(PEP):




Here is the Yaesu FT-1000 MkV (in Class A, with no ALC), down to -80db(PEP):




Here is the JRC JST-245:



Hope this helps some.  Smiley



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!  Smiley  
[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!  Smiley
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.  Smiley


73,

John,  KA4WJA
« Last Edit: April 25, 2018, 10:59:33 AM by KA4WJA » Logged
KM1H
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Posts: 5573




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« Reply #230 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?
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G0HZU
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Posts: 163




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« Reply #231 on: April 25, 2018, 03:16:41 PM »

I hope it's over...  Smiley

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.
« Last Edit: April 25, 2018, 03:25:06 PM by G0HZU » Logged
VR2AX
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Posts: 1016




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« Reply #232 on: April 26, 2018, 03:55:40 AM »

Possible proof reading error.
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KA4WJA
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Posts: 1098




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« Reply #233 on: April 26, 2018, 01:15:24 PM »

Carl, you're cool!  I really mean that!  Smiley  
It took me a while to realize it, but you're a good guy!

Me, done??  Nah, not likely... Smiley
Although, I don't have that much time these days....I'm not done.  Smiley
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.. Smiley
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!!  Sad
{BTW, how come nobody else caught this???  'cuz, even Zenki would cry BS on a IMD3 of -75db!!  Smiley 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
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G0HZU
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Posts: 163




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« Reply #234 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





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!
« Last Edit: April 26, 2018, 04:30:12 PM by G0HZU » Logged
K6AER
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Posts: 5745




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« Reply #235 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?
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K3LI
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« Reply #236 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.
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KM1H
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« Reply #237 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
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K9RJ
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« Reply #238 on: April 28, 2018, 10:57:06 PM »

http://audiosystemsgroup.com/TXNoise.pdf
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KM1H
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« Reply #239 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
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