Conrad and all,
The POWER control in WSJT-X is a misnomer. It is actually an audio
level control. Do NOT use it to control the power with an Elecraft
transceiver - set the audio correctly and use the power knob to control
the power.
While other amateur transceivers can be made to control the power by
varying the audio level, that can be disastrous for Elecraft transceiver
Power Control. Read the relevant article on my website www.w3fpr.com
for a full explanation.
Set the WSJT-X POWER control for 30% to 50% and do the same for the
soundcard control in Windows Mixer, then set the LINE IN gain in the
K3/S to somewhere near mid-range. By manipulation of those 3 audio
level controls, you should be able to achieve the 'magic' indication of
4 bars solid on the ALC meter with the 5th bar flashing - that is the
"NO ALC" point for the K3/S, KX3, and KX2 transeivers. The lower 4 bars
of the "ALC" meter are there as an aid for setting the audio levels.
Set the desired power output with the POWER knob - do NOT vary the audio
level.
73,
Don W3FPR
On 6/17/2019 9:38 AM, Conrad PA5Y wrote:
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?
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