Notes on the Recent Arlington - Salem Tests

Detectors are classified as of the relay or of the transformer type. Relay detectors are arranged so that the energy for the indicator response comes from a local source of energy at the receiving station. Transformer detectors utilise the received energy for producing the indicator response. The need of an amplifying transformer type detector, which selectively neglects static, is, mentioned. The basis of the heterodyne receiver, namely, the aud'ible beats produced by the interference of two vibrations of inaudible (radio) frequency received on a nonpolarized receiver, is then fully considered. Tho development of the heterodyne receiver, its circuit arrangements, and the apparatus- employed are described in detail. The use of the heterodyne in the Arlington - Salem tests and the results obtained are given.