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AM RF amp

Posted: Thu Oct 06, 2005 1:48 am
by jbprptco
Please help. Would like to buy/build/build from scratch AM RF amp approx 5/10 watts. Have US part 15 xmtrs with 100/300/500mw/1w to drive amp. Nothing available here in US that I can find. Thanks, JimB

Posted: Thu Oct 06, 2005 11:58 am
by pcs
AM requires linear amplifier operation.
Linear amplifiers are highly inefficient.

It is much better to modulate the final stage of a AM transmitter
and keep final stage in a highly efficient (but non-linear) C
or D/E stage.

This is why what you want to do will generate a lot of heat.
By the way, if you want a 10W carrier, you need 40W peak amp.

The best would be to run your exciter in full power mode (CW)
and take the modulating voltage and use it to modulate a new
stronger extra final stage.

Something like that can be done with AM MAX II DSP with PWM
modulator. PWM output stage can be reinforced with extra mosfets,
a new 100-1000W final stage added and you've got a really strong
transmitter that's also efficient. I believe someone in scandinavia
has done that with am max II.

Posted: Thu Apr 20, 2006 11:38 am
by static-steve
1kw sounds interesting, i am thinking about getting the AM MAX II DSP transmitter but i would require at least 500w to 1kw of power solid state. i have been offered a 2.5kw rig but it is not solid state.

Are 1kw amps hard to come by or would it be best to build a homemade one?

Posted: Thu Apr 20, 2006 2:43 pm
by pcs
You can roll your own. Its a fun project.