[Amps] Amplifier Distortion / Tuning / Etc. (EP Swynar)

[David Lisney]

Hi,
I am happy to accept that the 4CX250B family have their limitations, I run a 
conduction cooled version (CCS1) on 2m. Sometime I will post my screen 
regulator circuit somewhere for a reference. It consists of a simple 
constant current source feeding a shunt regulator, with some other 
protection incorporated.

My grid circuit is heavily swamped, partly to reduce the overall gain of the 
amplifier as I have a surplus of drive power available.

Interestingly a few veterans of 2m SSB have actually taken the time to give 
very positive reports, one in fact said "if you hadn't told me I would have 
never have believed that you were running a tetrode".

During one SSB contest I suddenly got a bad report from a local, I was 
beaming right through his location and operating very close in frequency, 
since he is a "serious contester" I quietly slipped away and went QRT. Away 
from the contest I found myself questioning what had gone wrong... too much 
drive.. too little idle current etc.

Went through loads of permutations before I found the villain of the piece 
was the processor in the driving rig!

In conclusion I am not suggesting for one minute we should not be seeking 
low distortion in our PAs but it is somewhat critical of clean drive!

Regards David G0FVT