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February 7th 04, 07:23 PM

umarc wrote in message ...
(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

Hallo Umar.

Thank's for responding. Atleast i have some transmitter type's wich
uses the 4CX type of tube's.
I did some searching on the net and found the Collins and the Harris
transmitters but no photo's, manuals or schematics wich i realy need
to bild this thing.
When i read Your story i understand a bit how they do it.....but a bit
is not enough.

Umar......thank's again for helping,if You know where i can find some
more info please let me know.

Regards. Onno.