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Author Topic: Flex power genious xl  (Read 5267 times)
M0HCN
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Posts: 566




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« Reply #30 on: April 08, 2019, 02:00:11 PM »

All too true, but if you think radio and RF are bad for 'cargo cult' "engineering", you should take a look at audio, sigh.

I concur with the ragging on 'appliance' operators, totally unreasonable IMHO, there are folks running black box rigs, in SSB  who are better at the operational side of radio comms then I will ever be, and more power to 'em.

On aerials I do so wish a few more people had read (and understood) "Fields and waves in communications electronics" before pontificating on that subject, but it is the internet, trying to correct all the 'not even wrong' would drive you mad, better just to grin hit next.

Most engineering is simple most of the time, but that is not the same thing as easy....
I sweated my way thru line and surface integrals so I could understand Maxwell, and use it about once in a blue moon in reality.
For every properly hard problem you hit in design there are dozens of stupid little 'datasheet clone' power supplies, IO ports and memory interfaces.

For the avoidance of doubt I am all in favour of education, but I am just a little leery of the formal route being right for everyone.

Regards, Dan.
« Last Edit: April 08, 2019, 02:02:34 PM by M0HCN » Logged
K6AER
Member

Posts: 5743




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« Reply #31 on: April 08, 2019, 02:38:32 PM »

A diplexer is not just to channel harmonics into a termination load but keeps the power from heating the device when power would be reflected under a normal low pass filter design. The third harmonic has most of the harmonic power in a solid state design application.

IMD, that is the  reciprocal mixing of a two tone signal has nothing to do with primary signal harmonics.

Isn't that what I said in my two posts above? I am trying to determine if there is a subtle difference that I am missing...

- Glenn W9IQ

Glen,

You and I posted at about the same time.
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KB6DYA
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Posts: 85




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« Reply #32 on: April 08, 2019, 03:41:56 PM »

To every one who submitted something Thank You. Just to remove any doubt I am a " appliance operator " I like rag chewing and that's about it. I just want the BEST sounding station I can get. I did all the experimenting and building 50 years ago and I do not care to do it any more. Mike thanks for comet about adding a beam would make things worse. Here is what I decided to do I have a Alpha 8410 with 4cx1500b tubes ( very clean ) I will sell my ic 7610 and buy a Anan 7000 or 8000 and add a 0 DB coupler to the output of the amp and feed that back as "pure signal " and keep the amp to 1k and watch the mic alc and I SHOULD have a clean signal.That is best I know how to do it.  Thank You KB6DYA Oren
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VK3BL
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Posts: 1790


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« Reply #33 on: April 09, 2019, 03:10:56 AM »

To every one who submitted something Thank You. Just to remove any doubt I am a " appliance operator " I like rag chewing and that's about it. I just want the BEST sounding station I can get. I did all the experimenting and building 50 years ago and I do not care to do it any more. Mike thanks for comet about adding a beam would make things worse. Here is what I decided to do I have a Alpha 8410 with 4cx1500b tubes ( very clean ) I will sell my ic 7610 and buy a Anan 7000 or 8000 and add a 0 DB coupler to the output of the amp and feed that back as "pure signal " and keep the amp to 1k and watch the mic alc and I SHOULD have a clean signal.That is best I know how to do it.  Thank You KB6DYA Oren

Firstly,
Apologies to those affected regarding my lack of understanding of the usage of '3rd harmonic' with reference to diplexer filters; I was conflating it with two tone IMD measurements as Glen picked up on.


Oren: Sounding the best and having the cleanest station are not the same objective, or even particularly compatible objectives.

IMHO <30dBm IMD3 & 5 is a reasonable standard; others will differ because they can achieve significantly better results into a dummy load (as have I) but achieving those levels in practice is another story.

Not everyone can do it, and if you set your heart on -50dBm (10,000x less energy) prepare to be disappointed when someone tells you you're only -20 on their built in band scope because they've left the NB on or whatever.

I suggest you take a look at some of your local AM BC stations on your scope, and see what IMD levels they're meeting.  Then consider the fact they were once fully engineered by the best and brightest, with antennas physically isolated from near field passive IMD producing structures etc etc. 

Be responsible in achieving a clean signal (don't overdrive everything), but recognise that achieving better than -30dBm IMD3,5 into anything other a closed loop system (aka a dummy load with a sampler and a receiver you control) is likely to be an exercise in diminishing rewards. 

Really, it can suck the absolute life out of the hobby trying to please both the 'golden ears' and the 'imd critics' at the same time.  I've been there, having purchased an ANAN myself and run pure signal etc.

Have fun, and realise that if you're on air, someone is going to complain sooner or later about something.  The amount of 'wide signal' FT8 reports I got working 80M DX from locals was amazing, I even got a screenshot from a guy accusing my station of being 40kHz wide!  40!!! 

I've recently setup a second station 10 miles away, and have never been able to reproduce the "issues" I've had people claim from time to time.  I wasn't able to using local monitoring, I wasn't able to using WebSDRs, and now I'm unable to detect any out of spec performance with another station 10 miles away.

The moral of the story?  Have fun and don't worry about the people who run PreAmp2 on 80M with the NB on and NR cranked up too (aka don't know how to setup their receiver), but feel the need to tell you how to set up your transmitter...

Oh, and don't tell the local DXers when you achieve DXCC on 160M or 80M.  Just my advice for what its worth Wink
« Last Edit: April 09, 2019, 03:16:34 AM by VK3BL » Logged

J.D. Mitchell BA  - VK3BL / XU7AGA - https://www.youtube.com/ratemyradio - Honesty & Integrity
VK3BL
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Posts: 1790


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« Reply #34 on: April 09, 2019, 03:51:23 AM »

Also, it's worth noting the IC-7610 and most 12v radios are significantly cleaner below 50W, where IMD5 stops becoming the dominant product and IMD3 emerges (this is a good thing as it reduces the overall bandwidth of your signal).

I believe the Alpha 8410 is quite a low drive amplifier?  If so, your current combination can probably achieve a very clean signal if you aim for a PEP power of 1Kw.  That would be about 30w drive from what I can tell from alpha's website.

I'd imagine you could achieve -40dB IMD3 with an output of between 800w to 1000w PEP (read with something like a Telepost LP-100), into a dummy load.

Be it solid state or tube, the greater the headroom you have, the cleaner your signal will be.  If you push things harder, you'll get thru the noise better, most likely won't sound any worse, but will have a wider signal.

Really, the best thing to do is to run the radio at low output into the amp (tuned for full power of course), and only dial up the power as needed for the QSO.  That way you'll always have a great sounding clean signal, and be least likely to upset others. 

Below 25w output, the IC-7610 is as clean as anyone realistically needs; go down to 10W or lower and you'd essentially have to say its running in Class A when you look at a 2 tone test.  I think I have plots on youtube from memory.
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J.D. Mitchell BA  - VK3BL / XU7AGA - https://www.youtube.com/ratemyradio - Honesty & Integrity
K6BRN
Member

Posts: leet




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« Reply #35 on: April 11, 2019, 08:45:24 AM »

Oren:

I hope you're kidding.  The IC-7610 is a fine radio.  I understand that you may be bored, and that's a reason to move on, but the ANAN will probably not be more satisfying - in fact, it's probably going to be quite frustating, so my advice is:  Don't burn your bridges."

Regarding (TD) IMD... there is just a little too much focus on that by just a few people in the ham community.  And some of them have really screwed up their own TX signals by trying to apply active feedback in ways they do not understand and can't measure.  Fixed and active equalization of TX signals is pretty much standard in my industry, and has been for decades.  Done wrong, it results in a lot of problems.  And I don't think the amateur radio community has a good, consistent and uniform (appliance operator friendly) approach to doing this.

Personally, my ham friends and I have had a lot more problems with IMD on the RX end, especially at repeater sites and special operations, like Field day and IOTA.  Passive intermod products (PIMs) and saturation of RX front ends in dense RF environments has long been a REAL issue in these cases.  But you don't really hear the IMD crowd chanting about this.  No "Torch to Carry" about equipment manufacturers gone wrong, I suppose.  PIMs will be a much bigger problem now that we're getting into use of weak signal modes, like FT8, in Field Day.  Dissimilar metals, some slight corrosion between key antenna components or support structures, bad connectors on coax... and who's EVER seen this on Field Day (Everyone who's looked), and PIM product will pop up on the waterfall all over the place.  Maybe 15-30 dB down - but, HEY, that's where weak signal modes look for contacts.

Have fun, always, and Best Regards,

Brian - K6BRN
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W3RSW
Member

Posts: 606




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« Reply #36 on: April 11, 2019, 11:51:42 AM »

Regarding IMD levels on commercial AM stations, yes it would be interesting to have a station eliminate the normal audio programming and put two equal tones or the three tone test (at three levels) on their carrier, otherwise we might confuse normal fully processed audio spikes for IMD on our typical, uncalibrated of course, but approximately representative SDR panadaptors. Grin

So I wonder what shows on a calibrated spectral analyzer at the same station using only two tone, etc.  Then When normal fully processed audio is run, IM3, 5, 7... may be superimposed on equal freq. audio spikes with all the concomitant overtones if just a few Hertz off, etc. and same for all the rest of the multitudenous, well infinite probably,  frequencies. A real cacophony. But somehow if not overdriven, or over processed, etc. really nice audio comes out of a decent receiver using decent demodulation of that station’s signal.  Grin
« Last Edit: April 11, 2019, 12:13:56 PM by W3RSW » Logged

Rick, W3RSW
K6BRN
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Posts: leet




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« Reply #37 on: April 11, 2019, 12:43:45 PM »

I used to live less than a mile from a commercial AM station.  IMD was the least of my worries.  It was the incredible amount of passively demodulated programming rubbish coming out of phones, unpowered speakers and (I kid you not) the decoupling caps on the power supply of an old Imsai 8080 computer I had that drove me nuts. (Hence the person who stands before you, today.)
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K6AER
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Posts: 5743




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« Reply #38 on: April 11, 2019, 01:17:58 PM »

Some interesting reading on Digital AM transmitters IMD.

http://www.measurement.sk/2004/S3/Horevajova.pdf

The White Paper is from:

Measurement of AM Transmitters for Digital Audio Broadcasting J. Horevajová, K. Ulovec

Department of Radio Electronics

Faculty of Electrical Engineering, Czech Technical University in Prague.


Looks like most transmitters are a bit better than -30 dB two tone.
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VK3BL
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Posts: 1790


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« Reply #39 on: April 13, 2019, 02:42:53 AM »

Regarding IMD levels on commercial AM stations, yes it would be interesting to have a station eliminate the normal audio programming and put two equal tones or the three tone test (at three levels) on their carrier, otherwise we might confuse normal fully processed audio spikes for IMD on our typical, uncalibrated of course, but approximately representative SDR panadaptors. Grin

So I wonder what shows on a calibrated spectral analyzer at the same station using only two tone, etc.  Then When normal fully processed audio is run, IM3, 5, 7... may be superimposed on equal freq. audio spikes with all the concomitant overtones if just a few Hertz off, etc. and same for all the rest of the multitudenous, well infinite probably,  frequencies. A real cacophony. But somehow if not overdriven, or over processed, etc. really nice audio comes out of a decent receiver using decent demodulation of that station’s signal.  Grin

It's not that hard at all to do.

Ignoring Ham Transceivers, one can use an SDR Play (accurate to ~1dB due to the design target of its ADC - demodulating QAM-256) and FFT averaging to get a good picture of the occupied spectrum.  Then just measure the power of the passband compared to the skirts.

Sure its not a '2 tone' measurement; its better!
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J.D. Mitchell BA  - VK3BL / XU7AGA - https://www.youtube.com/ratemyradio - Honesty & Integrity
VK3BL
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Posts: 1790


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« Reply #40 on: April 13, 2019, 02:44:57 AM »

Oren:

I hope you're kidding.  The IC-7610 is a fine radio.  I understand that you may be bored, and that's a reason to move on, but the ANAN will probably not be more satisfying - in fact, it's probably going to be quite frustating, so my advice is:  Don't burn your bridges."

Regarding (TD) IMD... there is just a little too much focus on that by just a few people in the ham community.  And some of them have really screwed up their own TX signals by trying to apply active feedback in ways they do not understand and can't measure.  Fixed and active equalization of TX signals is pretty much standard in my industry, and has been for decades.  Done wrong, it results in a lot of problems.  And I don't think the amateur radio community has a good, consistent and uniform (appliance operator friendly) approach to doing this.

Personally, my ham friends and I have had a lot more problems with IMD on the RX end, especially at repeater sites and special operations, like Field day and IOTA.  Passive intermod products (PIMs) and saturation of RX front ends in dense RF environments has long been a REAL issue in these cases.  But you don't really hear the IMD crowd chanting about this.  No "Torch to Carry" about equipment manufacturers gone wrong, I suppose.  PIMs will be a much bigger problem now that we're getting into use of weak signal modes, like FT8, in Field Day.  Dissimilar metals, some slight corrosion between key antenna components or support structures, bad connectors on coax... and who's EVER seen this on Field Day (Everyone who's looked), and PIM product will pop up on the waterfall all over the place.  Maybe 15-30 dB down - but, HEY, that's where weak signal modes look for contacts.

Have fun, always, and Best Regards,

Brian - K6BRN

Well Brian,

Theres something we completely agree on, a refreshing change hihi Smiley
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J.D. Mitchell BA  - VK3BL / XU7AGA - https://www.youtube.com/ratemyradio - Honesty & Integrity
K6BRN
Member

Posts: leet




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« Reply #41 on: April 13, 2019, 10:47:24 AM »

Hi JD (VK3BL):

Quote
Well Brian,  Theres something we completely agree on, a refreshing change hihi Smiley

Yep.  Nothing wrong with that!

Have a good one,

Brian - K6BRN
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G3RZP
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Posts: 1313




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« Reply #42 on: April 13, 2019, 04:02:52 PM »

To my mind, the average Joe Q. Ham these days is more limited in what he can hear and communicate with is limited by local noise from digital crap than from receiver IMD, spurious responses  and even high order tx IMD. Not that we shouldn't look at getting high order tx IMD down since the advent of solid  state transceivers has seen it get generally very significantly worse than the last generation of amateur transmitters with tube PA stages, but regrettably, external crap that no administration wants to bother with is really now the limiting factor in terms of reception for many amateurs in urban areas - and in some cases, even rural ones, too.

Interestingly, I hear that the SARSAT/COSPAS people are getting worried about the amount of noise at 406 MHz and its possibilities to reduce the capability of the Search and Rescue Satellite service to function effectively...

Individual equipment radiation limits came from CISPR, but nobody there considered the cumulative effects of lots of equipment. Plus CISPR seems more intent on having minimum standards regardless of whether or not they actually protect radio communication - to my mind as a professional engineer, they are an organisation well past their 'sell by' date who wants to protect manufacturers and allow them to radiate crap.
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VK6HP
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Posts: 544




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« Reply #43 on: April 14, 2019, 12:14:01 AM »

With quite a lot of professional life spent in radio astronomy and passive remote sensing, you'll perhaps forgive my chuckles at the mention of CISPR and other "standards" doing anyone much good. Yer on yer own, mate.

I do agree that there's a great lack of coherence in spectrum management and there is no doubt that in some cases users shamelessly exploit the cracks.  In other cases, technology uptake overtakes the byzantine nature of what coordinating bodies there are.  A case in point is the solar power industry, which is fast becoming the biggest contributor to the HF cesspit that characterizes Australian suburbs.  It is possible to implement fairly economical, radio quiet systems and, indeed, one of my current projects does that successfully for remote radio astronomy and HF communications installations.  Unfortunately, there's no incentive for such systems to be widely adopted in the consumer world.

I was impressed with the OP's wish to have a clean transmission, principally for reasons of personal pride if I'm reading his note correctly.  Far from dissuading him in that goal, I support his desire to have the best station he can put together.  While there are many inputs to the current cesspit, "everyone else is doing it" never has been a valid justification for contributing to any mess.  There are always choices to be made and taking the position of a passive consumer rather defeats the justification for having an amateur radio licence, in my view.

Of course, you're quite within your legal rights to team an FT991 (or similar splatterbox) with whatever dodgy, over-driven, solid state amplifier you can hunt up.  -20 dB, or worse, IM3 (etc) shows little concern for the spectrum environment or your neighbours, or much concern for your own signal quality, but you can do it - just as you can walk around smelly and dishevelled if you want. It's all about personal responsibility and standards.

This being ham radio, you get to largely set your own standards.  Perhaps you choose a middle path and choose to spend a little extra to get a very good exciter and conservatively rated amplifer - a reasonable thing to do.  Personally I aspire to do better as time and other factors permit.  I still enjoy operating my Collins 32S-3 and seeing distortion products below -40 dB and, conversely, I'm slightly pained by the knowledge that, in my "new" console, the heavily de-rated exciter/KPA-1500 combination (despite being a great integrated system) is no better than it ought to be in the IMD stakes. However, the path towards a viable pre-distortion system is emerging and I look forward to implementing it.

By the way, while passive IMD is a real effect and of great concern in many commercial systems (including cellular links), if it's worrying you in an HF/sub-2kW amateur station, you have some pathological issues with your installation that you need to address.  Fix those issues rather than using them as an excuse to pump more crap into the cesspit.

73, Peter.



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K6AER
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« Reply #44 on: April 14, 2019, 08:43:47 AM »

VK6HP –“ A case in point is the solar power industry, which is fast becoming the biggest contributor to the HF cesspit that characterizes Australian suburbs. “

Boy howdy is that spot on. Here in New Mexico near La Luz, there is a 20 acre solar farm. When I drive within a mile of the facility my HF noise level on the radio in the truck starts to rise. Twenty over S9 on 40 meters when I am out front.

Earlier this year several solar companies came out to the property to sell me on the idea of going solar. Only Arizona has a higher sun index. When I explained the interference problem, they were clueless. One said he would bring out a demonstrator trailer. A week later they arrived and showed me that 12 ea. 240 watt panels could generate over 2 KW of AC which would sync. with the grid feed and with the local utility approval, I could reduce my AC bill about $3.00 a day. Investment would only be $12,000. When they turned on the system it was 200 feet from my dipole. The RF noise was 30 over S9. They said I could turn off the system when I was on the air. I ask what about others in the area who use Ham Radio.  Silence.
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