[Milsurplus] BC-375

[WF2U]

Ron,

Congratulations for the nice find.

The BC-375 was the "liaison"  transmitter in many bombers in WW2, with the
BC-348 as the companion receiver. The ground version of the BC-375 is the
BC-191, they differ only in filament voltage arrangement and the matching
dynamotor since the BC-191 operated on 12V DC and the BC-375 operated on 28V
DC. The BC-191 was used with the BC-312 receiver. The tube lineup is
identical in both transmitters. The BC375/191 is capable of putting out
around 75-80 W in CW and 25W in AM (grid modulated).

They went out of fashion soon after they came out as surplus because if they
are handled properly,  they can be nasty TVI generators and had the tendency
to chirp badly on CW. The Conversion Manuals especially gave them the bad
rap, which is absolutely not true if the proper precautions and tuning
procedures are observed.  Load it lower than the MAXIMUM 230 ma, for 60 W
output and the transmitter stays stable, non-chirpy on CW and with good
audio on AM.
Hams have the tendency to squeeze out the last milliwatt that the system has
and if it becomes unstable, chirpy and/or distorted, then the transmitter is
blamed.
You can hear quite a number of BC-191/375's on several local "old military
radio" nets on the low bands and with the precautions mentioned above ALL
these transmitters sound good.
And lastly: don't use it above 40 M -  the stability is not good above that
band - stick to 160, 80 and 40 M

 With most people using  cable or satellite  TV nowadays,  the TVI problem
is not bad (or non-existent), especially in the suburbs and in the
country...

For the B+ you need 475 VDC and 1100 VDC (at about 350 ma),  and 24VDC for
the filaments and relays.
The original dynamotor is the PE-73 and they pop up  for sale every once in
a while.

Have fun with it on the air.

73, Meir WF2U
Gowensville, SC


 -----Original Message-----
From: 	milsurplus-bounces at mailman.qth.net
[mailto:milsurplus-bounces at mailman.qth.net]  On Behalf Of TVComlGuy at aol.com
Sent:	Monday, May 31, 2004 12:10 PM
To:	milsurplus at mailman.qth.net
Subject:	[Milsurplus] BC-375

I just picked up a very nice BC-375E in the box along with three TU's and
the antenna tuner.
Reading in my Surplus Conversion Manual it says that you shouldn't try to
put these on the air due to their instability.  Is this true?  I would  like
to
get this on 80 and 40.  Does anyone have a schematic for a modern  power
supply to supply the voltage for it or even an original power  supply.  I
have a
couple of Heathkit HP-23's that supply 700 volts at  250ma.  Would this work
for
the B+.  Any help would be  appreciated.
Thanks,
Ron, KB0WAR
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