[ARC5] Bendix System 3801 WWII Aircraft Set

[Mike Morrow]

A couple of days ago I took possession of an interesting WWII-era aircraft radio set made by the Pacific Division of Bendix Aircraft in Hollywood, CA, apparently of WWII vintage.

The set consists of receiver and transmitter RF stages in a small 6x14x6 inch (HWD) case that weighs about 10 lbs.  It is labeled as "System 3801."

The receiver section is further labeled as a "Model 3103 24," and covers 180 to 430 kc A2 and A3 modes, and 2300 to 6700 kc A1, A2, and A3 modes.  Dots on the dial scale mark 278, 3105, and 6210 kc.

The transmitter section is labeled as a "Model 3006 24," and has a single odd-ball crytal unit that contains three crystals (3105, 4495, and 6390 kc).  No doubt 6210 kc could also be covered by doubling 3105 in the PA stage.  The transmitter is a MOPA using a 60-turn roller inductor for PA tuning and a 8-step cap bank as a load control.  The transmitter unit functions in A1, A2, A3, or interphone mode.

The RT unit has *only* the RF and mixer stages for the receiver (12SK7, 12SA7), and the MOPA (12SK7, 1625)stages for the transmitter.  The IF, BFO, audio (12SK7, 12SQ7, 12SC7, and a 1625 plate modulator), and dynamotor (28 vdc in, 450 vdc at 210 mA out) are located externally on a 8x6x8 inch, 21 lb. power supply unit "Model 3206 24."  A 15-foot shielded 14-conductor cable connects the RT and PS unit together, using military-style Cannon AN connectors at both ends.

Overall, this appears to have been quite a capable little set.  Its plate-modulated 1625 covers four HF air frequencies that could be selected just as quickly as one could reposition the 60-turn PA inductor and the loading cap settings.  

The unit I have is all original and pristine on the inside, but has spotted, mottled, corroded areas on the front panel, and chipped and missing paint on the top.  The cases were very dirty and had a few dents, now straightened.  The shock mount screw holes show signs of the set having actually been installed somewhere.  The worst item was the plastic receiver dial pointer, which had dried up and curled way back so that it was pointing back toward the operator.  Some work with it in a plate of just-boiled water corrected that.

This is obviously not related to the many post-war light aircraft 3105/278kc sets.   It's somewhat larger and heavier, but also much more flexible and fully supports A1 operation.  The most interesting thing about this set is that "USN" and "U S in an anchor" marks are stamped on the RT unit, the PS unit, and the crystal unit.   The tubes are JAN-marked military tubes.

I wonder what use the US Navy had for this type of set.  One sees a lot of those USAAF ferry and observation craft radios of the RCA AVT-15/AVR-20 or AVT-112/AVR-20 series, but I've never seen anything like that for the USN until now.  The closest thing was the somewhat unusual BC-1206-CM2 (note the "2") beacon receivers, all of which I've seen have USN and anchor mark stamps.

Has anyone come across one of these before, or knows where the USN would have used them?

Mike / KK5F