[Amps] Some thoughts on a transistorized legal limit amplifier...

[Steve Thompson]

>   Now, recall this started with a class C amplifier,
> so a bit of inexpensive Digital Signal Processing
> (DSP) will necessarily be inserted between the mike
> and the exciter to provide for envelope restoration
> (linearization) of the amplifier via the PWM
> modulator.  The exciter will only be required to
> provide around 30 watts drive for this scheme to
> function.  Note that the exciter must be operated
> without compression, limiting, or ALC in this system. 
> Those functions may be included in the DSP section.
I think you'd need a feedback system - polar or cartesian loop, 
for example. The AM/PM in the output stage will be severe, and 
probably beyond simple pre-correction in open loop.

You can buy the whole feedback system integrated on a single chip 
these days, but all the uses I'm aware of are VHF and higher so I 
don't know if it will work at HF.

Steve