Following some reports of bad audio (confirmed by self listening), I
have been looking at my SSB adaptor in my K2.
So far I have reached the following conclusions
a) Its not RF leakage - running with a Dummy Load still creates it
b) If I monitor the RF output with my 100MHz scope, in CW the
amplitude is clean and stable and I can change its level with the power
control pot. If I inject a single audio tone into the mic input, then
the output is cleanish but keeps jumping in amplitude - approximate a
few times a second.
c) Looking around the SSB board, I make the following observations
(with the power control pot on about 10W)
The PWR CTRL line from Pin 6 on U2 slowly rises stopping at about
5.5v after 5seconds. At the end of its rail, it "jumps" a little.
The ALC THR line from Pin5 on U2 goes instantly to the correct value.
The Base of Q1 (VRFDET) jumps around
The ALC line (Pin 2 of U1) also jumps around
It looks as if I have something amiss around the level control loop on
the SSB card. It works ok on CW.
My K2 has been working fine for a couple of years now so it is strange
it has stopped. Any suggestions where to look?
73
Paul
M1CNK
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