I wonder if there are any 50KW AM vacuum tube transmitters in use anymore? I
read the excellent article about the Harris 50KW solid state xmtr that WLW
uses, pretty neat. In the sixties, what would be the plate voltage and current
for a PA running 50KW in AM? I'm sure they would use three phase input power,
but how much filter capacitance would be needed to insure a quiet carrier?
Always wanted to know.


I'm sure there are still a few RCA Amplifuzz's out there.

There are a pair of RCA BTA-50Fs (high-level plate modulated) in Cleveland.

The Harris MW-50 has tubes.

With a Harris DX-50 requiring only 86 KVA for 100 percent modulation, and an
RCA BTA-50F requiring about 150 KVA for 100 percent modulation, the economics
are heavily weighted in favor of solid-state 50 Ks.

The DX-50 can generate 50 kW from three voltages of about 200 volts and below
(see the Harris patent for details). The BTA-50F requires several kV (seven ?)
to do the same.

Almost all older transmitters of 5 kW and above were three-phase.

You could run a 5 kW or 10kW on a rotary phase converter if you were desperate.

50 kW requires three-phase, usually 277/480.