Measured Extremely Low Frequency Propagation Characteristics in a Simulated Earth-Ionosphere Model

The design and implementation of a physical model, simulating the earth-ionosphere space appropriate for extremely low frequency (ELF) wave propagation are described and propagation characteristics as derived from the measured model data over a propagation path up to 20 000 km and for a frequency range of 35-55 Hz are presented in this paper. Measured data on the ELF propagation in the form of amplitude and phase variations of a signal along the propagation path for various simulated ionospheric reflection heights are also discussed. The exponential signal attenuation rates in the form of dB/Mm are derived for various assumed ionospheric heights.