K3 QSK artefact

[David Cutter]

This is a re-post to see if it attracts comment.

This concerns an audible artefact using QSK cw mode.  When either rf gain or af gain are at maximum, there is an additional noise which accompanies the Morse characters.  This can be demonstrated as follows:

Mode: QSK cw, paddle sending string of dots or dashes ANY speed
power o/p: any, ie nil to max, dummy load or antenna, agc on or off,
filter: any, but more pronounced >1kHz
listening to monitor (side tone) on phones or speaker at ANY monitor setting

audio control: max
rf control: start low and raise until the artefact appears

or

rf: max
audio: low and raise until the artefact appears

at low speed the artefact sounds like a scraping noise riding on the string.
High speed it's like an extra edge.

The effect is also present with monitor at zero.  In this condition, the artefact itself can be heard without tone from the Morse characters:
a rushing sound is heard.  At a guess I would say it is digitally induced
noise.

This effect makes my K3 unusable on QSK, but does not occur on semi bk-in.  Anyone else heard this?  I think there must be a fault on my K3.  Please note, this is not receiver or band noise which is a long way down on this artefact.


David
G3UNA
K3 #547
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[Vic K2VCO]

David Cutter wrote:
> This is a re-post to see if it attracts comment.
>
> This concerns an audible artefact using QSK cw mode.  When either rf
> gain or af gain are at maximum, there is an additional noise which
> accompanies the Morse characters.  

I've noticed the phenomenon that you describe, but it's not exactly an
artifact. Looking at the audio output with a scope shows an absolutely
clean transition between noise and sidetone, or, if the sidetone is
turned down all the way, between noise and silence.

As the sidetone gets louder with respect to the noise, which occurs when
you turn the sidetone level up or the audio or RF gain down, you hear
less 'artifact'.

What I think it is is sort of an auditory illusion caused by the rapidly
pulsing noise, and maybe the sharp rise/fall times of the noise pulses
in between keyed elements (not the sidetone, which is shaped nicely).

I've suggested to Wayne and Lyle that they look at the way they ramp the
gain up and down in QSK, and Wayne has discussed the possibility of
making the tone quality of the sidetone user-modifiable. Maybe they will
look at this when they are done with more urgent matters.

In the meantime, if it bothers you, just change the balance between the
signal audio and the sidetone.
--
73,
Vic, K2VCO
Fresno CA
http://www.qsl.net/k2vco
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[David Cutter]

Hello Vic

I think to demonstrate the magnitude of the problem I am going to have to measure the audio level and compare it to a side tone at a particular setting.  Or, perhaps, make a recording and send it over for evaluation.  However, a qualititive statement might do for now:  at side tone (monitor) level of 12 which I find a happy state to listen to with real signals it is extremely intrusive and obliterates real signals coming through between elements.  Monitor would have to be near to maximum with audio below listening levels for real signals to make the ratio even approach satisfactory levels.  

If no-one else is getting this, it must be a faulty component.

I look forward to hearing others' experience.

David
G3UNA

>
>
> David Cutter wrote:
> > This is a re-post to see if it attracts comment.
> >
> > This concerns an audible artefact using QSK cw mode.  When either rf
> > gain or af gain are at maximum, there is an additional noise which
> > accompanies the Morse characters.  
>
> I've noticed the phenomenon that you describe, but it's not exactly an
> artifact. Looking at the audio output with a scope shows an absolutely
> clean transition between noise and sidetone, or, if the sidetone is
> turned down all the way, between noise and silence.
>
> As the sidetone gets louder with respect to the noise, which occurs when
> you turn the sidetone level up or the audio or RF gain down, you hear
> less 'artifact'.
>
> What I think it is is sort of an auditory illusion caused by the rapidly
> pulsing noise, and maybe the sharp rise/fall times of the noise pulses
> in between keyed elements (not the sidetone, which is shaped nicely).
>
> I've suggested to Wayne and Lyle that they look at the way they ramp the
> gain up and down in QSK, and Wayne has discussed the possibility of
> making the tone quality of the sidetone user-modifiable. Maybe they will
> look at this when they are done with more urgent matters.
>
> In the meantime, if it bothers you, just change the balance between the
> signal audio and the sidetone.
> --
> 73,
> Vic, K2VCO
> Fresno CA
> http://www.qsl.net/k2vco
>

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