ELF communication system design

Radio waves of frequency below about 1 kHz propagate around the earth-ionosphere cavity with very little attenuation. These waves also can propagate useful distances down into the ocean. They are attractive therefore, for providing long-range communication to submarines from a single site. By considering the various components of the communication channel in turn, the paper develops the design principles for such a system. Significant features are the use of insulated horizontal dipoles, grounded at each end, as the antennas, an optimum operating frequency below 150 Hz, non-linear processing in the receiver to reduce the effective atmospheric noise, and the large size but sparse installation density of the transmitting antenna.