[Amps] Help with ARRL handbook design 4CX1000A 2m PA

[Steve Thompson]

G4CLA wrote:

> Thanks for the reply. Yes I think you are correct, it is not a problem
> with the design but my specific amp, but how to find it?! I can drive
> the plate current to 800mA with about 10-15w of drive, which agrees
> with the expected figures in the design. Even at at 800mA the output
> power is only about 700W.

On the face of it, the anode load impedance is too low. Screen 
current can be an indicator of loading - what's that running at, 
and how does it vary as you wind up the drive power?

Steve