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

[Don Wilhelm]

Conrad,

Do check and adjust the Windows soundcard controls to mid-range. When 
set to extremes, it can cause clipping and distortion.

With the K3S, the internal soundcard will identify as USB AUDIO CODEC.

73,
Don W3FPR

On 6/17/2019 11:21 AM, Conrad PA5Y wrote:
> Don of course it is not a power control, that is obvious to me.
>
> I am very fortunate to have a lot of RF and Audio test equipment 
> available both at home and at work so I will measure what works best 
> and try to understand why. I will be happy to share my findings. I 
> will of course read your article. I am loathe to use the Windows audio 
> mixer, I would rather use an external passive attenuator. Maybe the 
> Windows mixer has improved, I need to check that with an audio 
> analyser. It used to be awful so I built an external passive 
> attenuator some years ago.
>
> I will be interested to see what happens to the K3S TX composite noise 
> when the power control is used. There is a certain very popular radio 
> where the AM noise comes up by 20 dB when the power is reduced from 
> 100W to 30W. I would be really pleased if the K3S power control works 
> properly!
>
> I bought the K3S purely for its TX PN performance.
>
> 73
>
> Conrad PA5Y
> ------------------------------------------------------------------------
> *From:* Don Wilhelm <donwilh at embarqmail.com>
> *Sent:* 17 June 2019 16:03:02
> *To:* Conrad PA5Y; elecraft at mailman.qth.net
> *Subject:* Re: [Elecraft] Next Question: DATA A with K3s and Fldigi
> 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 
> <http://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?
> >