"Ed Engelken" wrote in message
...
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.
==========================================
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

Thanks to all who replied, I really appreciate the responses. I always learn
something when I scan the posts here on this newsgroup.
Regards,
Tom

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.


Some RCA 5Ks and 10Ks were designed as two-phase, and, consequently, have four
rectumfier (sic) tubes.

This might be called a "four phase" rectifier in the same way as a three-phase,
full-wave rectifier is called a "six phase" rectifier.

Oh, these 5Ks and 5Ks actually run on three-phase feeders, as the primaries are
connected in a Scott-T, while the secondaries are connected as two-phase.

Buffalo and Philadelphia (including Camden, and undoubtedly RCA's plant as
well) were the last hold-outs of two-phase power in the U.S.

In article , inch (Peter
H.) wrote:

Some RCA 5Ks and 10Ks were designed as two-phase, and, consequently, have four
rectumfier (sic) tubes.

They were actually Thyratrons used as rectifiers, the plate voltage, and
hence power output could be adjusted by varying the firing angle of the
grid, sort of like the modern light dimmer in your dining room.

This might be called a "four phase" rectifier in the same way as a
three-phase, full-wave rectifier is called a "six phase" rectifier.

To avoid confusion I call it a 4 pulse, or 6 pulse rectifier, as the case
may be.

Oh, these 5Ks and 5Ks actually run on three-phase feeders, as the primaries
are connected in a Scott-T, while the secondaries are connected as two-phase.

Yes.

Buffalo and Philadelphia (including Camden, and undoubtedly RCA's plant as
well) were the last hold-outs of two-phase power in the U.S.

Are you saying that is what inspired RCA to build these transmitters with
a two phase feed to the rectifiers, I think they were the BTA-5G, BTA-10G,
BTA-5H, and BTA-10H?


Regards,

John Byrns


Surf my web pages at, http://users.rcn.com/jbyrns/

Buffalo and Philadelphia (including Camden, and
undoubtedly RCA's plant as well) were the last
hold-outs of two-phase power in the U.S.

Are you saying that is what inspired RCA to build these transmitters with a two
phase feed to the rectifiers, I think they were the BTA-5G, BTA-10G, BTA-5H,
and BTA-10H?


I am hypothesizing that RCA utilized some ingenuity and well-known (to
two-phase aficionados) engineering techniques to make an unusual box which had
some unique cost-savings features.


To avoid confusion I call it a 4 pulse, or 6 pulse rectifier, as the case may
be.


However "incorrect" it may be, the literature calls these "four phase" and "six
phase".

"Twelve phase" is also employed. This is really three-phase, full-wave, using a
"zig zag" transformer.