[AMPS] SB1000 parasite question for Tom and Rich+

[Jeff Wolf]

>  > <<  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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