Good Day All,
Just a "...final-final" in the matter of fixed mica / ceramic padder capacitors
in the final tank circutry of my 2x813 linear amplifier...
After I had removed & replaced my original series / parallel network of fixed
padders in the plate tuning of the tank circuit (with a combination of a
250-pfd. fixed vacuum capacitor & a fully-meshed 3.5 kv air variable placed in
parallel), I went one step further & removed the large doorknob cap that I used
to switch in parallel with the big 3-section air variable loading capacitor on
160.
The replacement in this instance was actually the air variable loading
capacitors --- placed in parallel --- out of a pair of junked Heathkit SB-400
transmitters that I have here. I had mis-givings about the "robustness" of
these rascals (the plates are not that far apart, if you've ever seen one), but
Bill Orr in one of his HANDBOOKS stated that a receiving-type air variable
capacitor is perfectly OK to use as a loading cap in a final pi-tank coil, even
if the amplifier in question was to be used in a (then) legal limit operation,
AND plate modulated!
Anyway, I'm happy to report that nothing has arced over thus far, and I have a
QSO with VK3ZL (thanks, Rob!) in the log from this morning on 160-meters to
prove it, Hi Hi.
Happy DX'ing & vy
~73!~ Eddy VE3CUI - VE3XZ
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