[AMPS] Dope question

Peter Chadwick Peter_Chadwick@mitel.com
Tue, 25 Apr 2000 17:20:52 +0100

Phil asks;

>But can someone explain to me why you can or can't use a linear on AM?  

You can. As the PEP is 4 times the carrier power for 100% modulation, a
linear rated at 1600w PEP out should only be driven to 400 watts of carrier.
You also need to make sure that the rating of the amp is such that it can
produce continuous carrier at one quarter of the PEP - sweep tube amps, for
example, tend to over-run the tube on the basis that the peak to average
ratio is low, and you can get away with it. Carrier is another matter -
especially as atrue AM op. is supposed to lock the PTT down for a 20 minute

One of the early RAF aircraft VHF transmitters used an 8018 (specially
slected 807 for full output at 120MHz) as a class C amplifier for AM. I
suspect there wasn't enough drive for it to be truly Class C and the quality
was described as dreadful, but it was done.......NOT RECOMMENDED!!!


Peter G3RZP

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