ELF propagation measurements

An experimental measurement program has been conducted to determine parameters for propagation in the 40-50 and 70-80 Hz range. These measurements have utilized a transmitter in Wisconsin radiating approximately 0.25W at 45Hz and 0.5W at 75 Hz. Simple sinusoidal signals have been received and estimated at several sites, some on the same great circle path. Sites have been located in Nova Scotia, Utah, Hawaii, Norway, Greece and Saipan. Based on a simplified propagation model it has been possible to estimate attenuation rates and mode excitation factors with high accuracy subject to some constraints which are discussed. Both daytime and nighttime attenuation rates and excitation factors are discussed.