on 3/23/01 12:59 AM, measures at 2@vc.net wrote:
>> At 28 MHz, the capacitance of the tube and
>> the capacitance of the tune Cap are on the same order of magnitude.
>
> 5pF is the same as 20pF?.
You forgot something, Rich. The tube socket adds stray capacitance. The
effects of putting the tube into the chassis adds stray capacitance. And if
your amp has more than one tube, those capacitances are all in parallel
meaning they add.
If I remember correctly, my 4-1000 has about 7 pf output C. However, in
some reading that I did and conferring with some others on it, I determined
that that actual capacitance in the circuit ended up being around 15 pF or
possibly even higher. I am sure that similar effects occur in the SB-200 or
SB-220, particularly since both these amps have more than 1 tube.
15 pF and 20 pF are quite close. That means that nearly half your
circulating current ends up flowing thru the tube(s).
73,
Jon
NA9D
-------------------------------------
Jon Ogden
NA9D (ex: KE9NA)
Member: ARRL, AMSAT, DXCC, NRA
http://www.qsl.net/ke9na
"A life lived in fear is a life half lived."
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