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February 6th 04, 05:48 PM

(Onno de Vries.) writes:

I hope that someone have experiance with big transmitters with
4CX5000A or simular in the final wich has about the same anode
cappacity and inpedance.
I hope that somebody can give me some Info about making a good and
high efficiend tank with these kind of tubes.

The Collins 830F transmitter used this tube -- there's one still in
service as a backup here in the Boston area -- and the tube socket
sits on the deck of a 1/4-wave-length cavity that can be tuned
roughly by raising and lowering a sliding plate that forms the
"ceiling" of the cavity. Fine-tuning is accomplished by moving a
vertical plate inside the cavity connected to the cavity wall;
it acts as a shunt capacitor. Another capacitor in series with
the output RF sample loop acts as a loading control.

The Harris FM-25K power amplifier is similar but is built around
a larger tube (8990/4CX20,000A).

umar
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