[AMRadio] AM Usage with Linear AMPS

W7QHO at aol.com W7QHO at aol.com
Mon Nov 22 20:23:27 EST 2004

In a message dated 11/22/04 3:49:55 PM, bcarling at cfl.rr.com writes:

> 50 watts AM output is surely not going to hurt a good ole 811A,
> LOL!

Going to shorten it's life considerably.   

To properly adjust a linear amp for AM it is necessary to tune the thing up 
for the peak power level, i.e., 200 watts for a 50W carrier.   The linear will 
be about 60% efficient at this output level.   Then WITHOUT CHANGING THE 
TUNING adjust the output from the AM exciter to provide for 50W out of the linear 
with no modulation.   The problem here is that the linear will now only be 
running about 30% efficiency under carrier-only conditions and the 811 would be 
dissipating something like 100+ watts.   The   811A, of course, is only rated at 
65 watts.

Dennis D. W7QHO
Glendale, CA

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