The description of the "ultimate amp" with separate pi-networks for each
band reminds me of an amp that my friend N5DX (SK) picked up at the Delta
Division convention one year back in the late seventies.
This was some sort of HF point-to-point commercial amp which was allegedly
used by the forest service. The tubes were a pair of 4-400As in grounded
grid with no tuned input. The output had six individual pi-networks to
cover the range of 1.5-14 MHz (if I remember right). Each pi network had a
roller coil with fixed doorknob tune and ceramic disk load capacitors. The
pi-networks were switched with a typical Radio Corp ceramic bandswitch,
which was motor driven.
I spent many hours horsing around with this amp for N5DX. He had a SB-220
for 80-10, so he was interested primarily in using it on 160. We added an
outboard bandswitch (DC) to control the motor drive, and by experimenting
with loading capacitors we were able to make it play on 160-80-40. The
power supply was nothing to write home about (the manual called this a
"400W" amplifier) but we were able to get 1000W out in "typical amateur
operation".
I wish I could recall the manufacturer of this amp. I often wished I could
find one of my own, for you could build a pretty decent amp from the basic
parts, and make it remote controlled as well!
73,
Dave/K8CC
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