Cathy,
What is that flaw in most 100W radios, Manfred?
It's the lack of coupling between the two sides (the two drains, or
collectors) of the push-pull stage.
In linear class AB or B push-pull stages the two sides need to be very
tightly coupled. Most of today's 12V 100W final stages don't provide any
of that coupling at all, and the few that do, achieve a good degree of
coupling only on the lowest bands.
And I'm not blaming the designers, in cases where they have no choice
but to use 12V supplies - I don't know myself how to achieve that
coupling, when the impedances are as low as 1.5 ohm per side. But the
logical reaction should be to reduce the difficulty by moving to a
higher impedance, which means a higher supply voltage. And then design
that coupling into the circuit!
Manfred
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