> On a suggestion I checked the oscillation with a scope. It agrees
> with my frequency counter - oscillation around 400 - 450 kHz.
> I failed to add in my first post... when this problem occurred
> during "normal" operation on 12M, the amp seemed stable during
> transmissions, apparently taking off at the moment of transition
> back to receive. That in mind, I am wondering if I should
> investigate the timing of relay and bias switching. This behavior
> may suggest the vacuum relay contact on the amp is opening before
> cutoff bias is applied.
> The other really ugly thing I failed to mention is that this
> oscillation would then continue until I toggled the amp
> operate/standby switch to standby. I suspect this LF RF is getting
> into places where there should not be RF.
> 73,
> Paul
27/03/2013 21:58
I think it's the 2011 ARRL Handbook that mentions LF oscillation in
linears, and I recall it mention input to output coupling issues, I
can type out the relevant paragraph if you think it may assist? It's
way beyond my experience, but I recall it mentions something that
sounds similar to your issues.
--
Best Regards,
Chris Wilson.
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