Original U.S. WWII BC-348 Army Signal Corps High Frequency Radio Receiver
Original Item: Only One Available. The Signal Corps Receiver BC-348 is a eight valve superhet all wave receiver produced in the U.S. during World War II in many different variants; it has mainly been in use as airplane onboard receiver, that's the reason for the remarkably light aluminum chassis and cabinet.
The receiver BC-348 comes in a relatively light aluminum case with black wrinkle finish, it is 46 x 23 x 22 cm (About 18" x 9" x 9") in size and has a weight of 20 kg. The BC-348 is intended to be powered from an airplane 28V DC power supply, the high tension is generated by a rotary converter, a so called "Dynamotor".
In the middle of the front panel, You find the frequency dial, a rotating round dial behind a dial window, a mechanical shutter let's You read only from the dial of the active band. The bandswitch in the form of a star shaped control is located just below the dial window, the tuning knob slightly below at the right. In the right lower corner of the front panel, You find the antenna and earth terminals and the antenna tuner control.
The on/off switch lets You select manual (M.V.C.) or automatic (A.V.C.) gain control, just below, You find the headphones jacks, volume control and the BFO note control. The BFO switch for the reception of CW and single sideband signals and the crystal filter switch are found just left of the main tuning dial window; a dial illumination control in the right upper corner lets You reduce the brightness of the dial illumination.
There are two pull out buttons to unlock the chassis, then it can be pulled towards the operator for changing valves. Remember this set was intended to use onboard planes, so the signal operator could not simply crawl under his desk to get access to the back of the radio to change a valve...
To operate the receiver, connect the correct voltage, a suitable antenna and an earth connection to the respective wire terminals. Set the power switch to A.V.C., now You should hear the dynamotor working.
Use the band selector to switch to the 6000-9500 kHz band and the main tuning knob to locate the signal of radio "Deutsche Welle" from cologne near the 6,075 MHz marks. Use the volume control to adjust the volume, the C.W. OSC switch should be set to OFF, it should only be activated when You intend to listen to morse code transmissions in the ham bands.
All controls seem to be a bit scattered over the front panel, but the receiver has many features of a more modern all wave receiver - remember, it has been designed in 1940 when front panel control ergonomics have not yet been a subject of discussion.
The BC-348 is a rugged and uncomplicated receiver to work on, but it is not easy to find a power supply delivering the correct power of 28V DC, sometimes You get problems with the mechanical dynamotor (works like a motor with a mechanically coupled alternator) and many sets have been modified to mains operation with a external mains power supply bypassing the dynamotor.
Technically, the receiver is as 28 V DC variant of receiver BC-224-B for airplane onboard use; technically it's based on the BC-224-A 14-Volt version developed by RCA in the middle of the thirties and in some parts on the improved B variant.
-The BC-348-B is powered by Dynamotor DM-28, it isusually mounted on a FT-154 / FT-167 shock mount. The receiver covers 1,5 - 18 MHz in six ranges.
-In models from BC-348-E and later. the longwave / VLF beacon range of 0,2 - 0,5 MHz has been added, the band coverage 1,5 - 18 MHz is now covered in only five slightly bigger band segments.
-In 1943, Belmont (Chicago IL) modified a number of BC-348-C for VLF reception, these sets have been given the new type number BC-348-S.
-All early variants BC-348-B and C have been built by RCA, they used a 41 as final audio tube.
-The variants BC-348-E, H, K, M, O, P, R have been built by Belmont (Chicago, IL), in contrast to the early BC-348 - variants from RCA, they used a 6K6GT in the final audio stage.
-The variants BC-348-J, N, Q have been built by Wells Gardner gebaut, in these sets, a 6K6GT is used as final audio amp, too; the sets from Wells Gardner can be recognized from the rotary knob to activate the BFO and from the lacking antenna tuner, there are some minor circuit changes.
This example is offered in excellent condition and appears to be complete but we have not tested it and do not guarantee functionality.
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