Electromagnetic properties of soil in the 500 kHz to 5 MHz range are determined experimentally to predict plane wave propagation. The ratio of the characteristic impedance of a coaxial probe filled with fluid or soil to the same probe filled with air is used to determine the material's effective permittivity and conductivity. Open‐ and short‐circuit impedances are measured, corrected, and used to predict wave parameters. Measurements made on dry desert alluvium demonstrated the method. Wave attenuation increased linearly with frequency between 0.5 × 10−2 Np/m at 1 MHz to 2.5 × 10−2 Np/m at 5 MHz because of increasing soil conductivity; the ratio of soil wavelength to free‐space wavelength remained approximately constant at 0.4 because of the almost constant permittivity in this frequency range.

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Napenille IllinoisABsIllAcT A numerical method is presented that can be used to analyze an infinite array of pyramid absorben such as those used in anechoic chambers excited by a plane wave of arbitrary frequency and angle of incidence. The method can be adapted to any absorber geometry. The problem is solved using Transmission Line Matrix analysis (TLM) over a mesh placed around one absorber pyramid. Link voltages exiting the side of the single cell are delayed by a phase factor dependent upon the frequency and angle of incidence and re-inserted into the opposite side. This effectively simulates an infinite array of such absorbers. The method works because of the fact that the exciting signal looks the same everywhere (except for phase). The method yields gross reflection coefficient as a function of frequency and angle of incidence for any given absorber shape.