Many vacuum tube 50KW AM out there?
 

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.
Regards,
Tom

In article ,
t.hoehler wrote:
I wonder if there are any 50KW AM vacuum tube transmitters in use
anymore?

They are certainly dwindling. I've visited a few sites that still
have Continental 317s active, but for the most part these transmitters
are being retired rather rapidly now, in favor of new Harris and
Nautel solid-state units.

The situation is less clear on the UHF-TV side. Many high-power UHF
stations still use Klystron-based transmitters, and newer high-power
installations still use tube-based transmitters.

-GAWollman

--
Garrett A. Wollman | As the Constitution endures, persons in every
| generation can invoke its principles in their own
Opinions not those of| search for greater freedom.
MIT, LCS, CRS, or NSA| - A. Kennedy, Lawrence v. Texas, 539 U.S. ___ (2003)

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.

In article , Garrett Wollman wrote:

They are certainly dwindling. I've visited a few sites that still
have Continental 317s active, but for the most part these transmitters

Especially since the older tube transmitters won't work well with IBOC
according to articles I've read in BE Radio magazine. You really need a
solid-state transmitter.

--
Sven Weil
New York City, U.S.A.

"Garrett Wollman" wrote in message
...
In article ,
t.hoehler wrote:
I wonder if there are any 50KW AM vacuum tube transmitters in use
anymore?

They are certainly dwindling. I've visited a few sites that still
have Continental 317s active, but for the most part these transmitters
are being retired rather rapidly now, in favor of new Harris and
Nautel solid-state units.

But aren't there still a lot of tube 50s in backup role? A couple of years
ago WTOP still had a tube rig as backup.

In article ,
R J Carpenter wrote:

But aren't there still a lot of tube 50s in backup role? A couple of years
ago WTOP still had a tube rig as backup.

At a lot of the sites I've visited, this used to be the case but has
changed in the not-too-distant past (or is scheduled to change soon).
A lot of the effort is due to IBOC, but even in its absence I've been
told that the advantages even of the ``Destiny'' over the original
DX-50 are sufficient to make it worth stations' while to buy one and
move their DX-50s to standby status. (It's a great racket for Harris,
certainly....)

Ten years ago it was pretty common to see a DX-50 as the main tx with
a Gates or Continental tube backup, but now -- among the full-timers
at least -- the usual state is two solid-state transmitters. Some
stations (particularly the ex-I-As) made a substantial investment in
solid-state transmitters and bought a pair of DX-50s when they came
out, or have a DX-50 and a 3DX-50, and alternate on a weekly or
monthly basis.

-GAWollman

--
Garrett A. Wollman | As the Constitution endures, persons in every
| generation can invoke its principles in their own
Opinions not those of| search for greater freedom.
MIT, LCS, CRS, or NSA| - A. Kennedy, Lawrence v. Texas, 539 U.S. ___ (2003)

"Garrett Wollman" wrote in message
...
In article ,
R J Carpenter wrote:

But aren't there still a lot of tube 50s in backup role? A couple of
years
ago WTOP still had a tube rig as backup.

At a lot of the sites I've visited, this used to be the case but has
changed in the not-too-distant past (or is scheduled to change soon).
A lot of the effort is due to IBOC, but even in its absence I've been
told that the advantages even of the ``Destiny'' over the original
DX-50 are sufficient to make it worth stations' while to buy one and
move their DX-50s to standby status. (It's a great racket for Harris,
certainly....)

Visit 980-Washington the same day as WTOP. They has 3 solid state rigs. A
Harris DX=50 for days, a Nautel 5 kW for night, and a Nautel 10 kW for
spare. Greater Media had done almost everything in at least triplicate. The
station was sold shortly thereafter and I wonder about the present
situation.

But aren't there still a lot of tube 50s in backup role? A couple of years
ago WTOP still had a tube rig as backup.

710 WOR in New York City had a Continental 317C as their main
transmitter until about 1997, when they replaced it with a Harris
DX-50. The Continental is now their backup transmitter. They use it
weekly during Joe Franklin's show -- the last music show left on WOR.

WOR also used the Continental during that big blackout a few weeks
ago. They chose it over the Harris because it's less sensitive to
power fluctuations. (Northeastern NJ had its power restored more
quickly than the City itself, but people reported voltage swings of
their household AC all the way from 50 to 148 volts, and I doubt the
three-phase power at WOR's transmitter site was any better controlled
at the time.)

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

"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

In article , Rich Wood wrote:
Maintenance, not sound is the reason. Very soon there will be a new
transmitter site across the street from the current one. As I recall,
the new site will have 2 DX-50s.

Why get new transmitters? Aren't the existing ones still good (and one of
them is pretty modern?)

Wouldn't it be easier to just move the existing transmitters, one by one
to the new site?

Why is WOR changing transmitter sites ... again?

--
Sven Weil
New York City, U.S.A.

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.

Why is WOR changing transmitter sites ... again?


The state is taking the site for a freeway.

The new pattern is quite different from the old one, although both are
asymmetric, three tower arrays.

WOR is being "ratcheted", even though the move is supposedly within established
limits for "walking" an array without such ratcheting.

(Another array design by the same engineer, Cynthia Jacobs, is also being
ratcheted, and under the same conditions).

WOR's nulls will be deeper, and will protect "notified" Canadian stations which
actually no longer exist.

What a pile of crap!

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.