FB-7 Series Coils

• alternative name: National Toy Co.
• Brand: Thrillbox

The National FB-7 Series Coils are wound on R-39 coil forms and are protected by a bakelite sleeve with a metal "handle" to facilitate removal from the receiver. (R-39 is a low-loss dielectric.) The coils also have National's special 6-prong base, which is not compatible with standard 6-pin tube bases or sockets. These coils are air-tuned.

Each band requires an Oscillator and Detector coil, and are marked "OSC" and "DET" along with the frequency range. These coils plug into the front of the receiver.

Coils were not supplied with the receiver. Each band cost $10 (US) per pair of coils.

Note: The original coils were air tuned, but the National Bulletin No. 240 from 1934 shows both air and mica tuned coil form options. It is unclear if these correlate to the FB-7 and FB-7A receivers, as National literature used the designations "FB-7" and "FB-7A" interchangeably. Also, it is unclear if the mica tuned coil forms were ever used for production models.

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