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

[Kevin, N4TT]

Hi Conrad:

I'm looking forward to your tests. I have things set up per Don's and Bob's
suggestions at the moment.

Windows level: -14.7db
fldigi level: -15.7 db
K3s level: 31

Again, I have not way to test quantitatively but the couple of comments
seems to indicate things are fine. I have this old KK7UQ IMD Meter which I
used to trust but it seems it's not working well or I need a new battery in
it. It's reading around -19 db IMD while my old rigs were at -30 easy. I'm
not trusting the meter at the moment.

Kev

On Mon, Jun 17, 2019 at 11:50 AM Conrad PA5Y <g0ruz at g0ruz.com> wrote:

> Don, it depends on the hardware. I would be very surprised if the Audio
> codec used in the K3S can reach full scale with the windows mixer at max. I
> expect that it is limited to -1dB FS. Also I believe that there are further
> limits imposed i WSJT-X. Therefore there should be no reason for clipping
> to occur in the CODEC.  I expect that there is sufficient range in the mic
> gain (or whatever it is called) on the K3S. This gives the input signal the
> maximum SNR which is the socially responsible thing to do.
>
> Until I have checked the behaviour of the windows mixer with the CODEC I
> will not be using it. As I have said previously I don't trust the windows
> mixer not to degrade the audio due  This may well have been resolved but
> historically was of concern.
>
> I think that I will decide what to do when I have made some proper
> measurements. It's not that I don't believe you, I just like to check
> things for myself.
>
> 73
>
> Conrad PA5Y
>
>
> ________________________________
> From: Don Wilhelm <donwilh at embarqmail.com>
> Sent: 17 June 2019 17:31
> To: Conrad PA5Y; elecraft at mailman.qth.net
> Subject: Re: [Elecraft] Next Question: DATA A with K3s and Fldigi
>
> 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>
> > <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?
> > >
>
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