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

[Steve Thompson]

Radio WC6W wrote:
  >    Back to HF, the DSP provides limiting to create the
> phase signal which is sent through the exciter at a
> constant (30 watt) level.  This will avoid the AM to
> PM problem.
> 
>    This is basically the Kahn EER scheme, from 1952,
> kluged to run with a typical transceiver in the signal
> chain.  If it worked back then, it should still work
> now! 

Sorry, I should have said the AM/PM I was thinking of was in the 
varactor effect in the semiconductor junctions when the output 
stage drain/collector voltage was modulated. I suspect that it 
would generate some distortion components.

Some of the original polar/cartesian loop designs were done on hf 
transmitters, round the tx system after the (conventional) ssb 
generator, so there weren't any narrow filters to introduce 
delays. It's something like 25 years since I did a prototype 
system for a mil manpack. It didn't use EER, but could have. In 
the end, the efficiency savings were outweighed by extra cost, 
complexity and functional problems. I imagine it would be 
different today.

Regarding class E PAs - some of the efficiency gain is lost of 
they are designed with enough margin to withstand mismatch, even 
just for long enough for protection circuits to operate.

Steve