AM Shunt Modulator

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wy3d:
Does anyone have any experience with using a Darlington pair in a circuit to modulate an AM transmitter without the use of a mod transformer.

KQ6F:
Probably not what you're looking for but here's a schematic for a 75M exciter I once built.  Not a lot of RF power but unmeasurably low audio distortion..

PA0NVD:
look to the thread "cathode modulation" You can modulate kilowatts with normal power FET's. It is NOT a series modulation but an efficiency modulation.

wy3d:
Very interesting on your transmitter.  Thanks! Thats pretty much what I am doing here on the bench.  I'm curious about the LM358.  Are you just using it as an audio driver?  I see there appears to be a feedback circuit from the emitter of the Darlington back to the inverted input of the IC.  What is the purpose of that?   I feed the base of the darlington directly with DC from a voltage dividing circuit to set the carrier level.  I see you are feeding the LM358.

wy3d:
I'll also check the posts on cathode modulation

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