[Elecraft] IMD and supply voltage

[Gary]

Walt,

Spot on.

It is frustrating to operate in a contest as much as I enjoy the challenge, the vast majority of strong signals are many times, disturbing to listen to.
I make a point of complimenting good audio even in the heat of battle.

Gary 

-----Original Message-----
From: "Luis V. Romero" <lromero at ij.net>
Sent: ‎30/‎10/‎2015 7:54 AM
To: "elecraft at mailman.qth.net" <elecraft at mailman.qth.net>
Subject: Re: [Elecraft] IMD and supply voltage

Bob, et. Al:

 

> 

>Signal reports heard being given today are largely "ego reports" and are 

>of little to no value.  When was the last time you heard a report 

>indicating ones audio is distorted, or sounds like the transmitter has a 

>bit of FM, or there's buck shot heard 10 kHz away, or there's a noise, 

>humm or a buzz on your signal?   Nope, we don't want to offend anyone 

>and thus seemingly just roll out a meaningless, non constructive 

>report.  I suppose to many of us have forgotten what we learned; "if you 

>can't say something nice, then don't say anything at all".

> 

 

Well, you obviously have not worked me :)

 

Audio transmission quality is a subject close to my heart.  While I
understand all the technical issues regarding Intermodulation Distortion in
12v vs 48 volt and Tube vs Solid State amps, the proof is in the pudding:
Just listen on the air! You will find folks running Class A rigs that sound
horrible due to overprocessing and the belief that turning all the transmit
audio knobs all the way to ELEVEN and seeing dancing meters make for great
signals.

 

Processor missadjustment is a worse culprit than IMD and, although IMD
products do harm, processor knobs turned all the way to the right are the
main culprit in the mess that has become our SSB subbands.  There are some
operators I can't understand at all.  Worse, some of the "Audio VooDoo" ESSB
types have so much bass that they create a phantom carrier, making their
signal copyable in AM mode.  On many of these, I even able to lock my
WinRadio SDR to the pseudo carrier in Synchronous AM mode!  

 

In the last CQ WW SSB, I started to think that my signal was too clean and
too bandwidth efficient versus my "competitors".  That lovely, raspy, sharp,
dense MP1000 sound (not to blame a particular radio, but I know how to make
that one sound that way), while certainly "penetrating", is difficult to
listen to, and, when overdone, makes it hard to understand.  That means lost
QSO's.  Want to increase your score?  Consider making better audio!  

 

Overdone processing by and large creates listener fatigue and
intelligibility problems.  A 10 second contest QSO, while not creating
fatigue on its own, when joined by 300 of them, will.  Wonder why you are
tired after a short stint on 40m in WorldWide Friday night?  This might be
the answer!    Transmitter IMD in this scenario is still there, however,
exacerbating the problem.  And some contesters will use their IMD "wideness"
as a weapon of advantage in the competition.

 

There is nothing we can do in our receivers to counteract this.  We are at
their mercy. Where is the Wouff Hong and the Rettysnich? We need you now
more than ever!

 

If we are going to campaign against anything, I would say campaign against
over-processing.  Once we get them to understand that issue, then we can
concentrate on IMD. 

 

With some of the signals I hear on the air today, IMD is the least of our
worry in a world where everybody is Fine Nine oh Five.

 

Audio quality is a very personal thing, like your car choice, radio choice
or your hair coloring chemical choices... I wish everyone had the common
sense to make articulate, clear, yet punchy and "communications quality"
audio by avoiding the temptation to eke out that last watt.  When we all do
that, then we can worry about Amplifier IMD.

 

Processing issues heard on the air today simply make the discussion of final
amplifier spectral purity moot.

 

Respectfully

 

Lu - W4LT

K-Line

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