The invention of the Superheterodyne Radio Receiver is attributed to Edwin H. Armstrong in 1918, whilst he was posted in France in WW1. The superheterodyne works on the basis of converting a high incoming radio frequency carrier to a lower intermediate radio frequency. The facilitates more controllable amplification and filtering. The superheterodyne principle is now universal and used by almost all radio devices manufactured since the 1930's.

Edwin H. Armstrong (right) with assistant and friend Harry W. Houck (left) with three superhet designs - The Signal Corps.set built in France (left), the pre-production 2nd harmonic superhet (center) and the production 2nd harmonic superhet, the 1924 Radiola AR-812 (right).

The documentation of the operation and early development of the superheterodyne may be found at the following links:

How Does a Superheterodyne Radio Work? (This excellent site details the historical background and practical theory of the superheterodyne receiver.)

Edwin H. Armstrong 1890 - 1954 (Here Mike Katzdorn has assembled an excellent collection of historical documents relating to Edwin Armstrong's career.)

RCA Radiola AR-812 was the first production superheterodyne radio receiver. It's commercial development was spurred on by the Radio Corporation of America in 1923. Prior to 1930, all RCA receivers were manufactured by either General Electric or Westinghouse and except for the do-it-yourself kit market, RCA refused to licence the superheterodyne to other manufacturers until after 1930.

The AR-812 appears most certainly a product of General Electric. I suspect it came out of the factory at Schenectady, New York in 1924 and 1925, but I am not sure of this.

I am in the process of restoring an AR-812. If you wish to follow my progress, please continue; I hope to share my experiences to all who are following a similar course!

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