US Navy marked Setchell Carlson BC-1206 CM2 radio range receiver

[BC312]

Bought a USAAF Seychelles Carlson BC-1206 C radio range receiver and managed to get it working with 2x 12 volt Batteries to make up the 24-28 volts needed to run it. Had some issues with the aerial and could pick up two stations on LW radio 4 etc here in the UK. Decided to buy another which I thought was only good for spares as the advert showed that the caps were different to normal and there was something not right at the back of the set that looked wrong in the photos but at a really low price good for spares.

When the set arrived it turned out to be a Navy marked CM2 model and what I thought was a tinkered radio by a radio ham turned out to be an untouched set all original. All the tubes are navy marked and the connections for the aerial are at the back rather than the side of the set on a terminal strip. There is also an extra connector for an output, not sure if this would be for a dial. The only down side is the missing casing, if anyone has one let me know. Just wondering if anyone would know what the output connector is for and if anyone had any information if the navy used these sets for marine boat use as there is mention that they were used for harbour use using the A-N radio range or 4 course range set up.

.

[BC312]

More photos

[BC312]

I tested this set at an airfield here in the UK and picked up 4 stations Crystal clear. So a useful radio that can at least pick something up, rather than some radios that are very limited. Thinking about using a 4000ohms LS-7 speaker than headphones.

[MIFlyer]

I have one of those, as well as a few of the Detrola set that was similar in terms of use but a bit different in design.

 

I do not believe that the terminal strip on the back is original. The original had the phone jack on the front, the antenna jack on the left side and a wire coming out of the back. That's all. The case would short out that terminal strip if installed.

 

Here is little write up i did on those sets:

 

The Cutest Aircraft Radios They Ever Made: The Detrola Model 438 and the BC-1206

 

In the 1940’s the standard aircraft radio navaid system in the U.S. was the AN Range. The AN Range predated the widespread use of Automatic Direction Finding receivers and used the 200-400 KHZ aircraft navigation band. Use of the system only required an ordinary AM receiver tuned to the band. Pilots would tune in the station that best corresponded with their destination, listen to the signal, and hear either the Morse code signal “A” which indicated they were to the left of the desired course, the Morse code signal “N” that indicated they were to the right of the desired course, or a continuous tone, which indicated they were right on course. Everyone with an aircraft sophisticated enough to have a radio used the AN Range, and so many light aircraft were equipped with only receivers for the 200-400 frequency that most control towers were set up to transmit on 278 KHZ for the purpose of giving landing and takeoff clearances to aircraft. For this reason, when the USAAF adopted the SCR-274N “Command Set” receivers and transmitters early in WWII, a standard equipment set consisted of a BC-453 receiver for 190-550 KHZ, a BC-454 receiver covering 3-6 MHZ and a BC-455 for 6-9.1 MHZ, together with a couple of transmitters, enabling coverage of both the AN Range as well as the standard control tower frequencies and other required military communications.

 

When the USAAF got to Europe, it found that the RAF had adopted VHF for fighter aircraft communications, using a crystal controlled set known as the TR1143. The Americans had to be compatible with the British when it came to fighters, and VHF gave far superior short range communications anyway, so the U.S. built the British set as the SCR-522, and adopted it as the standard radio for fighters, at least in Europe.

 

VHF was a big advancement but it caused a bit of a dilemma, especially for fighters operating in the U.S., which had to still use the AN Range for navigation. Overseas, low frequency beacons were less available and a lost fighter pilot would call for DF steer from a ground station. But fighters flown in the U.S., at least, had to have the low frequency receiving capability. Problem was, the SCR-522, while no more bulky than the SCR-274N receivers, transmitters, and modulator, still took up virtually all of the available room in the aircraft. Also, the fighters deployed to Europe would not necessarily require the low frequency capability, so an easy add-on capability was desirable to keep things as standard as possible.

 

The answer to this problem were the two cutest aircraft radios ever built; the Detrola Model 438 and the BC-1206.

 

Both the Detrola and the BC-1206 were designed to operate directly from 24VDC, without a dynamotor, and to be set up so that they could fit into a standard aircraft 3 inch instrument panel hole. They were small enough to be mounted directly in the cockpit with no more than a power lead and an antenna connection. Using their headphone jack, the sets could be plugged directly into the same audio circuit used by the SCR-522, so switching between radios was not required. They could be installed or removed within minutes without affecting the VHF installation.

 

The Detrola went into the later model P-38, P-51, P-47, and some P-63’s, fitting right into the cockpit, possible because the remarkably small receivers were only about twice the size of the control boxes used for the larger radios. The P-51 and P-47 had the little set right next to the pilot’s seat, facing upward at an angle, while on the P-38 it was to the right of the pilot’s seat, almost resting on the floor, facing up. On the P-61 it was in a rather strange installation behind pilot’s right shoulder, the dial facing forward. The P-63 manual I have describes the Detrola as a “portable” installation, even though it is bolted down under the main radio panel at the bottom of the instrument panel and the P-38 manual says the Detrola “may still be installed.” Presumably this indicates the possibility that the set was yanked out when the aircraft was deployed overseas. Interestingly enough, none of these installations used the set’s ability to be installed in an instrument panel hole. All installations used long wire antennas; on the P-51D, the Detrola antenna is the long wire coming through the hole in the top of the bubble canopy and stringing back to the tail.

 

In contrast to the Detrola use and installations, the only manual I have found that mentions the BC-1206 shows it installed in a side instrument panel hole in a P-80A, the early model Shooting Star jet fighter.

 

The two sets fulfilled an identical function and were clearly made to identical specs, but are actually quite different electronically. I have always assumed the Detrola and BC-1206 were just related models of the same radio but recently found out they are very different. The Detrola Model 438 was made by the Detrola Company, and employs five standard WWII type octal tubes, including a VT150 oscillator/mixer and a couple of 6L6’s for audio output. The BC-1206 was built by Setchell Carlson and uses five 14 volt loctal tubes like the 14A7 and 14J7 and a 28D7 output tube. Both have an unusual antenna spring loaded lead socket on the left lower side near the front, use a combined volume/on/off switch, and have a ¼ inch headphone jack on the front. While the tuning knob on the Detrola simply operates a geared pointer against a frequency dial painted on the face of the set, the BC-1206 has a window over a dial to show the selected frequency.

 

While the Detrola was used extensively in the U.S., I don’t know if it actually went to combat. However, the period photos of P-51’s in Europe show the long wire antenna, even though an SCR-522 usually can be seen behind the pilot, so one would presume those wire antennas were hooked to something

 

Postwar, the Detrola and BC-1206 were replaced in refitted WWII aircraft and the newer jets by the BC-453 and/or the new ADFs such as the ARN-6 and ARN-7. No doubt the larger sets were much better receivers, - but they were not half as cute!