[AMRadio] Pi-Net vs Link Couple

W7QHO at aol.com W7QHO at aol.com
Fri Sep 23 00:54:05 EDT 2005

In a message dated 9/22/05 7:30:13 PM, w5omr at satx.rr.com writes:

> that's interesting, Darrell... a reactor in the screen supply.  Are you
> capacitivly coupling it, as well?  No, that can't be - the screens need
> to be DC voltage.  However, the choke effectivly kills any stray
> capacitances...

A choke in series with the screen supply exhibits a high impedance at audio 
frequencies and allows the screen to self modulate.   The technique has been 
around for a long time.   A screen dropping resistor of sufficient size will 
provide the same effect.   The military T-368 does this with an 80K screen 
dropping resistor off the 2500 volt HV supply and applies modulation to the plate of 
4-400 PA only.   The same technique was applied in the T-195 (4X150D PA, 1KV 
plate supply).

Dennis D. W7QHO
Glendale, CA

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