" I just noticed in this ad: http://hamstation.com/ybstkftmk5.htm that
Yaesu's FT-1000 finals are MOSETS in push-pull. I don't ever recall
seeing a pair of final tubes in an xcvr or linear in push-pull except
perhaps way back in a very old QST. Can someone explain why push-pull is
used in the Yaesu and why we don't see it in "modern" tube amps?
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Tube amps with 2 output valves can be used in push- pull but then for 1 band
only unless you would switch multiple inductors.
A single valve or multiple valve in parallel can readily output into a
multi-band PI filter arrangement.
In QST -March 1967 , pages 11 - 15 there is an article on a 1kW amplifier
for 50 MHz with 2 pcs 4-125A or 4-250A or 4-400A push pull . This is a
single band amplifier with inductive coupling on in- and output.
Unless you would perform band switching by changing the inductors through
plug-in , switching for various bands would be very complicated.

Frank GM0CSZ / KN6WH.