Extremely Low Frequency (ELF) Propagation Measurements Along a 4900-km Path

Extremely low frequency (ELF) electromagnetic wave propagation was investigated by measuring the amplitude of a CW signal transmitted from the Sanguine site in North Carolina to receiving sites located in New York State, Labrador, and Iceland. The attenuation factor α and the reciprocal of the excitation factor
h_{i} (\sigma_{e}S_{0})^{1/2}
were determined. Data for daytime, nighttime, and sunrise transition paths were obtained. The attenuation factors obtained for 78 and 156 Hz are compared with the value of α obtained from measurements of atmospherics. The attenuation values at 78 Hz of 1.29 and 1.01 dB/1000 km, and a value of 0.75 dB/1000 km at 45 Hz, obtained by interpolation of results of this and other experiments, were used in Sanguine systems analysis.