2M GU-78B PA
made by KOTEL,
OK1BAF

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This amplifier uses a GU-78B with a 1/2l anode line.

This tube is capable of up to 4KW output at 144MHz, but tube life is short at that level. This particular PA is to be operated at about 750W out; the tube lasts a VERY long time at this lower level and is virtually free of intermodulation products.

More information, diagrams, schematics, etc., will be added as they become available. I have not been able to translate the text which accompanies the original OK1BAF presentation at http://www.ok1baf.wz.cz/m/m.htm.

Click on picture for zoom

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33   Ua - 3100V not load
Ua - 2500V Full load
Ia - 1.5A
Ia - 4A peak
Ug1 - 72V
Ig1 max - 10mA
Ug2 - 315V
Ufil - 27V (28V for EME)
Ifil - 3.5-4A
60W in
4000W out for EME
Cath. circuit swamping eliminates oscillation
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Cathode circuit swamping network consists of 16 x 600W resistors and 8 x 300 pF capacitors. Two of the resistors is series with a capacitor appear in eight places around the socket (see picture, below, right).

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Last Updated: 13 February 2004
Feedback: Paul S. Goble, III, ND2X
Copyright © 2004 by ND2X and OK1BAF, all rights reserved