"Lynn Coffelt" wrote in message
...

"K3HVG" wrote in message
. ..
Lynn Coffelt wrote:
Keith Martin, W7KGV used a rig that was a wonder
to watch. Whole
garage
floor covered with used automobile batteries, charger
working 24/7 for a
few
days, then the fun began!
BC-375 (from B-17's and B-24's) ran off 28vdc.
Motor generator
turned
out 1000vdc for the rig. Basically an MOPA
(remember????) with a VT-4C
oscillator and another for PA. (now the VT-4C's around
are for
audiophile's
output tubes... some now referred to as 211's)
The MOPA transmitter worked on all bands, with
proper tuning unit,
up
through 20 meters. Best output was on lower bands, 40
meters was Keith's
favorite, as his "off-center fed extended Zepp" antenna
fit on his lot,
with
just a little over on the neighbor's lot.
Keith could contact "ZL's" in the evening, with
reports ranging
from
336 to 589C. (Honest operators always included the
"C"in the signal
report,
as the BC-375 had a distinctive "yooup di dit dit"
which the "C"
designated
as a chirp, but was closer to a Yooup) It got really
distinctive when
the
batteries ran low, and the filaments dimmed and the
motor generator
almost
stalled on long CW dashes.
Keith eventually mastered a "bug" and increased
his operating speed
so
more than one contact could be made before the
batteries went dead
again.
Receiver was the venerable BC-312, which had a
handy crank on the
tuning knob to follow the "state of the art" signals as
they drifted
around
the band.
Some, who disliked drifting around on the bands,
invested in a pile
of
FT-243 surplus crystals for other rigs, that didn't
eliminate the
friendly
and reasuring "chirp", but didn't make drifting so much
of an issue.

Old Chief Lynn, W7LTQ




Lynn, Not a few of us currently have BC-375's and '191's
on the air,
regularly. With a bit of tweaking, FMing can be
"minimized" but they
still drift. I'd like to find the xtal control mod that
CAP used in the
50's for these rigs! Power supply wise, fortunately,
currently there
are supplies capable of running (at least) the DY-88 24v
dynamotor and
ac HV supplies are also around for both. They do present
a very
impressive setup when the BC-348 or BC-342 are included,
along with the
other SCR- accouterments. Look for some of these on the
Old Military
Radio Net, an East Coast, early morning net on Saturdays
on 3885.

One can't buy a new and complete SCR-284 for about $100
anymore, but
nice gear does show up from time to time. I was lucky
and got a new
one a few years ago.... a time machine, to be sure! de
Jeep/K3HVG

Wow! I'm going to have to try listening! I don't
remember hearing a
BC-375 on AM phone!
Around 1959 I got mine new and complete for $50.
Another young man had
just paid $75 for it and decided he didn't want it any
more. After using it
a few months, I tore it up for parts and ended up with a
push-pull final
amplifier. (using the VT-4C's, of course, and the plug-in
coils borrowed
from another friend's BC-610) Always had some remorse
about parting out the
BC-375 with it's tuning units, and antenna tuner, but sure
had a lot of fun
building stuff with the parts.
The modulation transformer worked great in a much
later (1958) home
brew 15 meter rig. Oh, how the bands rocked in those days!
Old Chief Lynn, W7LTQ


My first transmitter was a BC-375-E which I had
modified to work with an external exciter. I used it on AM
with a preamplifier to allow using a dynamic mic instead of
the carbon mic the input stage was designed for. I even had
this thing on sideband using a Barker and Williamson SSB
generator and some self bias for the amplifier stage.
Probaby the only Class-A linear on the air but it worked.
Mostly, I used it for CW where it worked very well.
The exciter was completely home built using an electron
coupled oscillator circuit copied from a General Radio
frequency meter. Given a reasonable warmup it was very
stable.
I still have this rig in storage but its too large for
my current situation.


--
---
Richard Knoppow
Los Angeles, CA, USA

"Richard Knoppow" wrote in message
...

"Lynn Coffelt" wrote in message
...

"K3HVG" wrote in message
. ..
Lynn Coffelt wrote:
Keith Martin, W7KGV used a rig that was a wonder
to watch. Whole
garage
floor covered with used automobile batteries, charger
working 24/7 for a
few
days, then the fun began!
BC-375 (from B-17's and B-24's) ran off 28vdc.
Motor generator
turned
out 1000vdc for the rig. Basically an MOPA
(remember????) with a VT-4C
oscillator and another for PA. (now the VT-4C's around
are for
audiophile's
output tubes... some now referred to as 211's)
The MOPA transmitter worked on all bands, with
proper tuning unit,
up
through 20 meters. Best output was on lower bands, 40
meters was Keith's
favorite, as his "off-center fed extended Zepp" antenna
fit on his lot,
with
just a little over on the neighbor's lot.
Keith could contact "ZL's" in the evening, with
reports ranging
from
336 to 589C. (Honest operators always included the
"C"in the signal
report,
as the BC-375 had a distinctive "yooup di dit dit"
which the "C"
designated
as a chirp, but was closer to a Yooup) It got really
distinctive when
the
batteries ran low, and the filaments dimmed and the
motor generator
almost
stalled on long CW dashes.
Keith eventually mastered a "bug" and increased
his operating speed
so
more than one contact could be made before the
batteries went dead
again.
Receiver was the venerable BC-312, which had a
handy crank on the
tuning knob to follow the "state of the art" signals as
they drifted
around
the band.
Some, who disliked drifting around on the bands,
invested in a pile
of
FT-243 surplus crystals for other rigs, that didn't
eliminate the
friendly
and reasuring "chirp", but didn't make drifting so much
of an issue.

Old Chief Lynn, W7LTQ




Lynn, Not a few of us currently have BC-375's and '191's
on the air,
regularly. With a bit of tweaking, FMing can be
"minimized" but they
still drift. I'd like to find the xtal control mod that
CAP used in the
50's for these rigs! Power supply wise, fortunately,
currently there
are supplies capable of running (at least) the DY-88 24v
dynamotor and
ac HV supplies are also around for both. They do present
a very
impressive setup when the BC-348 or BC-342 are included,
along with the
other SCR- accouterments. Look for some of these on the
Old Military
Radio Net, an East Coast, early morning net on Saturdays
on 3885.

One can't buy a new and complete SCR-284 for about $100
anymore, but
nice gear does show up from time to time. I was lucky
and got a new
one a few years ago.... a time machine, to be sure! de
Jeep/K3HVG

Wow! I'm going to have to try listening! I don't
remember hearing a
BC-375 on AM phone!
Around 1959 I got mine new and complete for $50.
Another young man had
just paid $75 for it and decided he didn't want it any
more. After using it
a few months, I tore it up for parts and ended up with a
push-pull final
amplifier. (using the VT-4C's, of course, and the plug-in
coils borrowed
from another friend's BC-610) Always had some remorse
about parting out the
BC-375 with it's tuning units, and antenna tuner, but sure
had a lot of fun
building stuff with the parts.
The modulation transformer worked great in a much
later (1958) home
brew 15 meter rig. Oh, how the bands rocked in those days!
Old Chief Lynn, W7LTQ


My first transmitter was a BC-375-E which I had
modified to work with an external exciter. I used it on AM
with a preamplifier to allow using a dynamic mic instead of
the carbon mic the input stage was designed for. I even had
this thing on sideband using a Barker and Williamson SSB
generator and some self bias for the amplifier stage.
Probaby the only Class-A linear on the air but it worked.
Mostly, I used it for CW where it worked very well.
The exciter was completely home built using an electron
coupled oscillator circuit copied from a General Radio
frequency meter. Given a reasonable warmup it was very
stable.
I still have this rig in storage but its too large for
my current situation.


--
---
Richard Knoppow
Los Angeles, CA, USA


SALUTE, Richard!
You really took that great rig for a ride! Mine was also a BC-375E, I
did try the T-17 microphone once with a guy using a NBFM adapter, and he
reported me working just as well on AM as NBFM! (or maybe phase modulation?
who could tell the difference?) CW was best, especially when one could get
the antenna to load where you could hardly find the plate "dip" anymore, and
looong dashes caused the graphite plate to glow a little red! Wow!

Old Chief Lynn, W7LTQ