Pappenfus et al. (and even Eimac) explain why the curvature produced by
grid current in AB2 can cancel IMD. But it won't do it in 4-400s without
proper circuitry in terms of NFB and regulated supplies. To say AB2
invariably gives poor IMD is a unjustifiable, rather sweeping, statement.
The SWR point is valid, but as my transceiver has a hollow state PA , it
matters not to me! Of course, if the PA has a low enough output impedance,
it doesn't matter, which, if I remember, was why people used triode
connected neutralised 807s as drivers to pairs of 805s in the very early
days of amateur SSB. Use a 200 watt driver and a 3dB attenuator.....
The perfect amplifier wouldn't be commercially viable, since everyone wants
something different - I want auto tune, for example. And a total cost not
exceeding 10c/watt. Which can be done by homebrew, although I'll admit that
amateurs who actually build equipment are getting about as common as teeth
on hens!
73
Peter G3RZP
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