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.
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Tom:

Don't know about the 50 kW tube transmitters, but the RCA BTA-5F (5
kW) transmitter at KTSA in San Antonio Texas ran 9 kV on the plates of
the RF final (single 892R) and modulator (pair of 892R's). The RF
final plate current was around 780 mA. This transmitter was in use
from 1949 until well into the 1970s. I worked there from 1958 to
1961, so I don't know exactly when it was phased out of operation.
The BTA-5F used three-phase power and a full-wave rectifier with
6-each 8008 mercury-vapor rectifier tubes. Don't remember the size of
the filter capacitors, but they weren't extraordinary as I recall. The
filter choke was about as big as a full-sized microwave oven.
Full-wave rectified, three-phase power isn't hard to filter.

Best Regards,

Ed
Canyon Lake, TX