[Elecraft] K2: KPA100 transmitted audio distortion 80 meters

[Don Wilhelm]

Dick,

It puzzles me that it only appears on 80 meters.  Do change R4 back to 
100k - the higher voltage is not required with the updated KPA100 (blue 
toroids), and is undesirable.

Do you have the KPA100 ribbon cable and speaker cable tucked up into the 
corner of the KPA100 and dressed as far away from the KSB2 board as 
possible? (remove the right side panel to check and tuck-in if necessary).

Do you have the KI6WX increased gain mod on your KSB2.  If so, have you 
made the corresponding changes to the ALC section of the KSB2?

73,
Don W3FPR


radiotelegrapher wrote:
> I have moderate distortion of transmitted SSB audio from my KPA100, but ONLY
> on 80 meters.  The distortion seems worsen and improve from time to time,
> with no apparent reason, and tapping components doesn't give a clue. 
> Listening on a nearby receiver, and transmitting into a dummy load on 80
> meters, the audio consistently sounds fine with the KPA100 off (at 10 W and
> less), but is distorted with KPA100 on (at 11W and higher).  The distortion
> is particularly noticeable at the start of a new syllable, which sound like
> a loud crack.  A constant amplitude, like a tuning fork by the microphone,
> sounds fine, so I suspect the TR switch or ALC.  My build is Rev 3, Jan. 18,
> 2007.  Searching the archives, I've found the usual causes, but the fixes
> are already included on my build:  C31 is .22 mF, and R33 (1K) parallels
> RC3. I tried changing R4 from 100K to about 39K, but it didn't help.  Any
> ideas?  Dick, K0KK
>   
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