QSK CLICK

[Henry Gardiner]

Fred and others,
   I've lost track of who originated what mod to eliminate that QSK click
that started for me when I installed the DSP option into the K2.  What
provided a good enough solution for me was the 100K resistor in series with
pin 17 /MUTE of the MCU U6 on the control board.  Why this worked I can't
tell you for sure.
   The down side is that I think I had to remove a soldered IC so I could
cut a trace and install the resistor.  Getting the IC out was no problem
for me since I have the appropriate vacuum desoldering equipment and
experience to do it without hazard.  Then too maybe I'm confusing this mod
with another mod.
   Under some conditions - maybe 1-3% of the operating time - a light
thumping remains in my full range headphones for short periods from unknown
causes.  It's so transitory that I never did anything further about it.
   Looking further down the road: One thing I found important is that the
BFO has to be stable if the DSP is to track the crystal
filter.  Spectrogram in waterfall mode works quite well using noise to see
how well the two filter systems track as the K2 warms up.  If the K2 is
connected to a stable signal generator putting out a signal on the K2's
receive frequency, one can also check to see how the PLL reference
oscillator is doing as things warm up.  The line for the received carrier
and the width of the two passbands should ideally maintain a constant and
rational relationship.
   I ended up gluing an LM34DZ temperature-reading IC to the ground plane
between the PLL reference crystal and its associated varicaps.  This feeds
an opamp which in turn feeds a correction voltage via a high value resistor
to the varicaps.  Now the drift is somewhere between 0 and -3 Hz from a
room temperature cold start to the maximum QRP sustained key-down 5W output
temperature with the lid on.  However, the crystal quality control has
quite likely been improved since my #4017 and maybe most people get good
results with the stock solution.
   I added a similar pair of ICs in the BFO area to correct the BFO.  The
results were +0/-3 Hz or better over the same temperature regime.
   I run the filter gain in the DSP at about -6db to avoid flat-topping of
the signal in the DSP just outside the corners of the passband.  This
avoids the harsh sounds.  The best setting could be expected to change from
rig to rig.
   My narrowest DSP filter width is the minimum that can be set - 40Hz I
think.  Using the 'soft' filter response for this setting avoids most of
the ringing.

73s, Henry AC5LA

   

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[Don Wilhelm-3]

Hi,

For anyone wanting to add the 100K resistor on the /MUTE line, there is no
need to remove an IC - the trace from pin 17 of the MCU runs over to C23 on
the front side of the control board  - that trace can be easily cut and the
resistor added from C23 to U6 pin 17 on th eback of the board.

73,
Don W3FPR

----- Original Message -----

> Fred and others,
>   I've lost track of who originated what mod to eliminate that QSK click
> that started for me when I installed the DSP option into the K2.  What
> provided a good enough solution for me was the 100K resistor in series
> with pin 17 /MUTE of the MCU U6 on the control board.  Why this worked I
> can't tell you for sure.
>   The down side is that I think I had to remove a soldered IC so I could
> cut a trace and install the resistor.  Getting the IC out was no problem
> for me since I have the appropriate vacuum desoldering equipment and
> experience to do it without hazard.  Then too maybe I'm confusing this mod
> with another mod.
>   Under some conditions - maybe 1-3% of the operating time - a light
> thumping remains in my full range headphones for short periods from
> unknown causes.  It's so transitory that I never did anything further
> about it.

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[Fraser Robertson]

This is a new one on me, as is the recent suggestion of increasing C72 from
10 to 100n on the KPA100.

I get QSK clicks regardless of whether the PA is enabled or not, so I
haven't tried the C72 mod.  I have the KAF2 audio filter, no DSP.  I have
1M0 in parallel with R17 (3M3) to speed up the QSK.  Will the 100k /MUTE
line mod help reduce the clicks?  Any feedback would be appreciated.

Thanks / 73 Fraser G4BJM   #4368


>For anyone wanting to add the 100K resistor on the /MUTE line, there is no
>need to remove an IC - the trace from pin 17 of the MCU runs over to C23 on
>the front side of the control board  - that trace can be easily cut and the
>resistor added from C23 to U6 pin 17 on th eback of the board.
>
>73,
>Don W3FPR

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