Of all the military Services, the Navy was the most interested in airborne signals intelligence prior to the beginning of the war. Installed on many of their patrol aircraft, the General Electric RAX-1 trio provided a continuous search capability from 200kHz to 27 MHz, as well as doubling as a fine liaison receiver capability. Shown here is the entire set, including the junction box and shock mounted racks.

This receiver had a number of unique characteristics, including excellent stability and performance. For example, it used fairly conventional circuits but plate voltages that were 2/3 of those in most other designs. The dynamotor on the rear of the receiver provided 160vdc, lowering noise and extending tube life. A single antenna could be daisy-chained through all three receivers, and was carefully isolated by filters to avoid local oscillator interference between receivers. For unknown reasons, this 1940 GE RAX design followed the ARC's circa 1934 Type K in using the concept of plug-in shelf racks for the receivers. (See The Original "Command Set" for more on the Type K.) The approach may have been driven by a Navy design specification, but I haven't yet located any documentation on it. In any case, the RAX had a more complex execution of the idea than the ARC design - it required special aluminum castings in both the receiver and rack, adding unnecessary weight and expense to the design, but was none the less an elegant engineering solution. The built-in tube puller for each receiver was a wonderful idea, though the cad plated steel is slippery and could have benefitted from a rubber or plastic coating on the business end. ARC offered a servicing kit that had an almost identical puller, but it wasn't attached to every receiver.

One of the more frustrating collection challenges has been the search for the uncommon connectors. The RAX uses a 4 pin "coarse thread" Cannon connector that I've seen on no other piece of WWII equipment. To compound the problem, the entire set (with junction box) requires seven of them! Below is a photo of the triplets installed below an ATC/ART-13 in a Navy PB4Y2:

This set originally began in a 1940 contract in a slightly different form. The initial manual for the equipment covers only receivers with serial numbers 1 to 75, and displays a single rack for all three receivers, shown here.