[ARC5] BC-1206-CM...and other WWII Beacon Band Units

[Mike Morrow]

> also a 512 model that is for 12volts but this requires a separate B+ supply about
> 150v will do ..different tubes..may be made by Detrola but no maker on mine..

Definitely not Detrola.  Detrola made the Model 438, BC-1206-A, and BC-1206-B,
which are all basically the same.

The 12-vdc filament model is the Setchell-Carlson Model 512.   In military service,
The Model 512 has the JAN nomenclature of R-76/ARR-13, and it was used with the
RCA AVT-112 HF transmitter and AVR-20-A1 HF receiver set in 12-vdc light observation
aircraft.  These three units used one AVA-126 vibrator supply for HV, which was
250 vdc.

RCA made an AVR-15 beacon band receiver that is the same size as the AVR-20-A1.
The AVR-15 is considerably larger than the S-C Model 512, and also lacks the RF stage
found in the Model 512 (AN/ARR-13).  I suspect that led to the use of the AN/ARR-13
rather than the AVR-15 in these applications.

> ...the 512 has a switch for a single beacon frequency or the normal 200 to 400khz.

No.  That switch selects three pre-adjusted capacitors to place the receiver on
278 kHz, which was the most common **tower** transmission frequency of the pre- 
and post-WWII era.

There is another Setchell-Carlson beacon band unit...the dry-battery-powered
S-C Model 591 (A and B batteries are required).  In military service it is the
AN/CRR-1, and it was intended as the receiver companion to the SCR-578-* (BC-778-*)
500 kHz "Gibson Girl" hand-cranked emergency transmitter for USAAF aircraft
operating over Arctic regions.  It operates from 190 to 420 kHz.

So, common beacon band units of the WWII era in US military service were:

Detrola Model 438
Detrola Model 438 (BC-1206-A)
Detrola Model 438 (BC-1206-B)
Setchell-Carlson Model 512 (R-76/ARR-13)
Setchell-Carlson Model 524
Setchell-Carlson Model 524 (BC-1206-C, two major mechanical variants)
Setchell-Carlson Model 524 (BC-1206-CM)
Setchell-Carlson Model 524 (BC-1206-CM2)
Setchell-Carlson Model 591 (AN/CRR-1)
Ranger Model 111-C (BC-1206-D) 
RCA AVR-15

IIRC, there are some tube-line up variations between the BC-1206-A and -B models,
and the BC-1206-C, -CM, and CM2 models.

IIRC, the main difference between the BC-1206-CM2 and earlier Setchell-Carlson
beacon band Model 524 receivers is that a square four-pin Jones plug was used
at the rear for the power connections.  I don't have a schematic for mine, but
it is child's play with an ohm-meter to figure out the +28 vdc, common, and
(maybe) AF output connections on ANY of these beacon band units.

Mike / KK5F