[Elecraft] Next Question: DATA A with K3s and Fldigi

[Don Wilhelm]

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?
>