[Milsurplus] BCs 638, 639, 640

[Cletus W Whitaker]

de WB2CPN South Central Pennsylvania  2003.11.23

Marty, from 1946 to 1966 I was in the USAF AACS and
the AFCS where I installed, maintained, and overhauled
the BC-639/BC-640 combination, and I never once heard
of an SCS-1 or 2.  The original collocated configuration
placed the BC-639 in the control tower or whatever
operating room where the operators could get at the knobs,
the BC-640 was downstairs, and the antenna relay connected
all this to an RC-81 balun-matched vertical dipole antenna.
The small diameter antenna elements, (three sets to cover
100 to 156 MHz), were upgraded to one set that looked like
they were made out of beer cans.  After years passed the
upgraded version of the BC-640 which had only one meter
showing came out. Along about 1954 when the USAF came
out with the AN/FRC-19 control tower, and the AN/FSA-4
approach control the transmitter sites and receiver sites
were separated by a couple of miles or more.  The first
time I ever heard of it, in about 1951 we remoted both
the BC-640 and the BC-639 from K-2 Tageu in Korea to the
top of a mountain about 4 miles crow fly away.  And, I
came up with a way to use AN/TRC-1 with CF-1 and CF-2
bays and ringers to do it. (I have pictures of all this!)

The BC-638 and BC-639 power supplies would run on 110 or
220 VAC, 50 or 60 cycles.  As you know, the bottom of
the BC-640 rack held a AC voltmeter with a red mark at
220 volts, a 7 KW "Variac" to adjust the meter reading,
and a bread box size autotransformer to permit operation
on 110 VAC.  It was a single phase set up, not three
phase.  This is all in the tech manuals.  If the facility
had a three phase feed it would be separated and used
as single phase to various equipment.

In my experience fighter squadrons, etc, used aircraft
radios and 28 volt supplies for their communications.
If the radio broke it was easy to just swap it with
one from the radio shop.  The 522 worked better if the
case was changed to include a good fan blowing through
it.  AN/TRC-1 was designed for Radio Relay, but I don't
think it was used in WWII.

And, the BC-640 didn't eat 24G's if it was neutralized
and tuned properly. The plates are not supposed to run
so white that you can see the grids through them.

73 all    Clete