[AMRadio] Pi-Net vs Link Couple


Jim Wilhite w5jo at brightok.net
Fri Sep 23 09:55:31 EDT 2005



W7QHO at aol.com wrote:
> 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 
> the 
> 4-400 PA only.   The same technique was applied in the T-195 (4X150D PA, 1KV 
> plate supply).
> 
> Dennis D. W7QHO
> Glendale, CA


This same thing (choke) is used in the Globe King series of 
radios by WRL  The resistor scheme is in the DX 100, etc.

73  Jim
W5JO




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