Alan,

I comment on one part of your reply:

To Bob, I think
the efficiency of the PA is only high if you calculate the input power to
the
'total' output power (wideband), the harmonic power doesnt 'improve your

QSO

getting potential' surely as its in the BC band in Europe!! Isn't it the
case that the harmonic power is not reflected back to the the PA , where

it

could cause trouble but the input to the diplexer can still be a square
wave, giving high efficiency in terms of the heat generated on the

heatsink.

The "squarewave" action in the PA devices is basically why the very high
overall efficiency is possible.  The squarewaves could be thought of as
having harmonics (a la Fourier series) but they could more simply be
regarded as inclusive of "hard switching" where there is minimal coincidence
of voltage and current (the product being dissipation).  The squarewaves are
"beneficial" and could be considered as reducing the heating compared to
them not being present.

73, Bob