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Diffraction and Refraction of Radio Waves

Nature volume 142, page 681 (08 October 1938) | Download Citation



THE increasing application to various radio purposes of ultra-short electric waves of less than 10 m. in wave-length has given a new stimulus to the problem of calculating the field strength at distances from the transmitter such that the ionosphere is of negligible influence. The solution of the problem of the diffraction of electric waves around the earth was first given on a sound basis by G. N. Watson in 1918, but this analysis involved assumptions which, while perfectly valid for the long and medium waves then in use for radio communication, are not justifiable for the ultra-short waves now being considered. For example, at long wavelengths, the conductivity of the earth may be assumed to be infinitely great for analytical purposes, but as the wave-length is reduced through and below 10m., the actual value of the conductivity and also the dielectric constant of the soil over which the waves are propagated has an important influence on the field strength at a distance from the source. Furthermore, the height of the receiver above the earth's surface may no longer be assumed to be a negligibly small fraction of a wavelength, when the latter is only a metre or two.

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