> > << The fix that seems to work is: reduce VHF
> > amplification. >>
> > Rich it seems to me that one way to reduce vhf gain would be not to use
> > tubes ( very expensive ones) that have max. ratings to 500 mhz on
> > frequencies of 30 mhz or below. HANK
>
>Sound practice!
Actually not. The maximum usable frequency of the device has
nothing to do with stability.
Tom,
So what you are saying is that a 3-500Z will oscillate at 1 ghz just as well
as a 2c39?
Seems that whatever tube has a tendency to oscillate at VHF would also stand
to sustain a parasitic oscillation at VHF when used in the HF range... Or
do the laws of physics and common sense not prevail in RF?
On a side note, I noticed in quite a few of the "10 meter" amplifiers of
yesteryear, (with multiple sweep tubes) manufacturers placed ferrite beads
at the anode clip. This tamed many a amp from eating tubes (with the
subsequent "big bang")... Seems that the ferrite would also act as a
reatance at VHF, too.
--Toll Free
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