Ken,
A bias control circuit with temp tracking is in order.
Examples have been detailed in past ARRL
Handbook Projects and the famous Motorola
RF Data Applications (notes).
Cheers,
Skipp
--------- Forwarded message ----------
From: KE2N@cs.com
I have a mirage 300 w brick with a similar biasing scheme. It had
terrible SSB linearity until it "warmed up". I increased the forward bias
so that it was clean cold, but now it goes into a kind of thermal runaway
when it gets hot (draws 40 amps contiuously - class A!). My cure was just
to put a really big fan on it so it does not get hot. A less-than-ideal
situation. A "real" bias circuit would certainly help. I don't think any
of the Mirage amps have them.
Ken
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