Bringing another RBZ back to life

And what have we here ? I unpacked an old, somewhat worn, box with the partial label indicating it was "Model RBZ Equipment" and "US Navy". After a short Internet search, it looks like these were used in WWII as "Marine Raider" receivers to receive commands from team leaders and later, with expanded frequency coverage, given to Resistance fighters in Europe to monitor transmissions from the BBC. Interesting bit history, although the military use is unconfirmed by firsthand experience. If you have any firsthand experience with these units, please send me a note and I'll include it. The Internet has quite a bit of information on these receivers, especially the I0JX website.

The box says this is serial #1331, which matches the number on the receiver. There are only two controls, ON/OFF/Gain and Tuning. The tuning knob is "push to tune" to prevent accidental de-tuning by bumping the knob. The edge marked 2.1-5.8Mhz dial is one of the old radium units for night time viewing and the numbers are readily visible through the small plastic dial face. The superhet receiver uses 5 miniature tubes; 1T4 RF Amp, 1R5 Osc/Mix, 1T4 IF Amp, 1S4 Det/ AF Preamp, 1L4 AF Output. It is permeability tuned, and The design and the construction appear excellent and well thought through (a minimum of components). I've seen 5 of these radios now and all were made by Emerson Radio and Electronics (Emerson Radio and Phonograph Co.) and have RCA tubes.

The receiver connects to the soldier's helmet with a thumbscrew clip to provide an antenna. The receiver and it's battery power unit are housed in identical waterproof phenolic housings. Both are carried in a canvas pouch along with the headset. The headset is a skull cap to be worn under the helmet and contains two thin headphones labeled "CARRON US-42". Reception is excellent.

The battery box originally contained two 1.5V "A" batteries for the 5 tube filaments and a 67.5V "B" battery for the B+. The 1.5V batteries are easy and the 67.5V battery can easily be substituted by using seven or eight 9V batteries in series (fits nicely).

Here are the component numbers. US Navy identification consists of a prefix which defines the manufacturer/supplier followed by a numerical item identifier, so the prefix may be different (CEX is Emerson).

All the components of the RBZ receiver in it's canvas bag

RBZ Receiver, side "a"

RBZ Receiver, side "b"

RBZ Battery Power Unit