As part of a trade for a medium wave BC transmitter that I recycled, I
received a large package via UPS last evening. Inside was a Broadcast
Electronics FM1.5A power amplifier drawer. The sticker said 1989. It
still had the 8877 plugged in. It is a half-wave circuit made from 1
inch copper water pipe, folded in the re-entrant style that BE got a
patent for in their larger cavity amplifiers. I had forgotten what the
thing looked like, but in 1982, when I was a youngster at BE, I worked
with old-timer Bill Harness (deceased now) who had come from
Harris/Gates Radio. He was the champion of water-pipe amplifier
circuits, along with Mr. Hoyt at Harris (also recently deceased). Bill
designed the thing from scratch, and I made a bet that I could model his
line circuit with a simple transmission-line code in Basic, which I did.
Both turned out to work as expected, approximately at the desired
frequency.
The package yesterday reminded me of the simpler times, when I
introduced Bill to using a Network Analyzer (albeit, a crude HP-8754A)
to supplement his Grid Dip meter, neon lamps and sharp lead pencil. The
thing still had hose clamps holding the copper cone to the anode of the
triode, and still had the original HV bypass capacitor that I had
designed using two sheets of etched copper-clad Kapton (Pyralux). I am
not sure where this thing will go, being almost a museum piece now, but
it might make a good start for a kW on 2 meters or other for EME and
weak signal work. Now if I can find the rest of the transmitter.
73
John
K5PRO
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