Historically there were all kinds of low level artefacts produced by Windows
audio algorithms, including the volume control. This was caused by insufficient
precision leading to truncation artefacts. I have not tested it for a while and
so it may no longer be the case. The result when I did test it was spectral
smearing and some AM on what should be a constant envelope signal. I trust the
power control in WSJT-X far more than that from the Windows mixer. These
effects only really matter during weak signal conditions when your TX signal is
on or near the noise floor. at the receiving station However they do make your
signal wider.
Also be careful how you vary power, reducing audio carelessly will invariably
decrease the signal to noise on your TX signal which will also affect a
stations ability to receive you.
My K3S arrives this week and I will make some tests to see exactly what happens
with TX composite noise when power is reduced with the power control and by
reducing audio drive from the PC. Unless someone else has measured this already?
73
Conrad PA5Y
________________________________
From: elecraft-boun...@mailman.qth.net <elecraft-boun...@mailman.qth.net> on
behalf of Bob McGraw K4TAX <rmcg...@blomand.net>
Sent: 17 June 2019 15:13
To: elecraft@mailman.qth.net
Subject: Re: [Elecraft] Next Question: DATA A with K3s and Fldigi
Kev:
First the ALC indication should be, no.... must be, 4 bars solid and the
5th bar flickering. To monitor your signal, use the MON function of
the K3S. It should sound VERY clean. If there is buzz, growl, humm or
anything besides pure tone, there are issues to be resolved. Check all
PL-259 connectors in the signal path to assure they are very tight. I
use a pair of 4" Channel lock pliers to snug mine.
As to levels -18 dB is 30% for the SPKR level from the computer. That is
what I use. Then the level adjustment {lower right corner} in FLDIGI is
running -10 dB and the Line Gain on my K3S is running at 30. Then
set the PWR value on the radio to the value of your choice, I normally
run 50 watts without the KPA500. With the KPA500 I run 300 to 350
watts. All of these numbers work for WSJT-X / FT-8 as well.
As to things "looking good", I rely largely on the software and IMD
reports. I also have a 2nd receiver and computer where I can monitor
my own signal if need be.
Seems you just need to tweak levels a bit to get things in a more normal
and balanced level condition.
73
Bob, K4TAX
On 6/17/2019 12:50 AM, Kevin, N4TT wrote:
> My first PSK-31 contact seemed to go very well. I simply adjusted the MIC
> level (Line) until there was 5-7 ALC bars. The adjustment was quite smooth.
>
> Then I went off and did other things and I'm concerned I changed something.
> Now I have to turn the level way way down on the USB Audio CODEC (-16.4
> dB). Then I add another -3 dB using fldigi. Finally, I adjust the Mic to
> Line = 17. The Mic adjustment isn't smooth.
>
> The major change was the addition of the KAT500 and KPA500 (stby) and I'm
> wondering if either I messed up a setting or maybe created an opportunity
> for some RF feedback that's affecting the audio.
>
> At this point, I don't know how to confirm the signal is clean (especially
> PSK-31). I've only had one report of a possible problem and a number of
> reports of "things look good" so I'm calling that a wash.
>
> I found nothing in the instructions that told me to drop the level of the
> USB Audio CODEC and -16.4 dB seems like a big drop. The CODEC is set for 16
> bit, 48000 Hz.
>
> Am I worrying about nothing? Is your setup with fldigi and DATA A using the
> K3s's internal sound card similar?
>
> Thanks for your patience.
>
> 73,
> Kev N4TT
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