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Old December 30th 09, 03:35 PM posted to rec.radio.amateur.boatanchors
Scott Dorsey Scott Dorsey is offline
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First recorded activity by RadioBanter: Jul 2006
Posts: 774
Default Advice on class-C modulated tube

Antonio Vernucci wrote:
I sometimes tend to be perfectionist, and I would then not like to start a
project pursuing a compromise solution from the very beginning. So, I would like
to have the screen modulated too, not just the plate.


I think that if you do this, you have higher audio distortion even though you
have a slightly higher modulation level.

With regard to the separate audio amplifier for the screen, it should work but I
am not sure whether some phase shift could occur between the two amplified audio
signals (apart from the 180-degree phase ambiguity that can be easily resolved
crossing the wires of one of the two modulation transformers).


It depends mostly on how well matched the modulation transformers are. Most
of the group delay will be the result of the transformers.

Better to use a transformer with two secondaries than two individual amps.

I have come to the conclusion that using a filter choke on the screen probably
is the simplest way to go, and the safest for the final tube too.


Is the best possible fidelity important to you? Is having a tiny little bit
more modulation important to you? I think in the manuals to the Bauer 707
broadcast transmitters there is a paragraph or two about the compromise.
--scott
--
"C'est un Nagra. C'est suisse, et tres, tres precis."