On a sunny day (22 May 2006 07:47:53 -0700) it happened "Telstar Electronics"
wrote in
.com:

Jan,

Sure you can run class D at 27MHz... the problem is distortion. Class D
is very efficient but is really only meant for digital signals.

www.telstar-electronics.com

Hi, you know class D audio amps exist I suppose?
There are even class D power amp chips for audio.
These use PWM (pulse width modulation).
You can make any output waveform with PWM (as long as the switching frequency
is much higher then the output frequency).

This links shows some basics for a modulator (driving class D for example):
http://www.netway.com/~stevec/ham/pd...lid_state.html

I can also think of a 'digital' solution, say you have 8 RF amps,
1W, 2W, 4W, 8W, 16W, 32W, 64W, and 128W,
now simply switching these on with an 8 bit digital audio signal (one on each
bit) and summing the RF output together, will give you a 255W AM modulated
transmitter with less then 1/255 (0.4 percent) distortion (have not tried)?
Since these RF amps can be class C (no need for A, AB, B, any linear!!) you
should get good efficiency.
The stages are only 'on' or 'off'.

So, maybe someone could combine some :-)
Nice for experiments....
hehe