Radio Propagation over Spherical Earth

The paper shows how Watson´s solution for the propagation of electromagnetic waves over perfectly conducting spherical earth merges into the Abraham solution for propagation over a perfectly conducting plane for shorter distances. The effects of refraction by the lower atmosphere and of the imperfect conductivity of the earth are taken into consideration. The magnitude of the former, which is appreciable, is obtained. The latter is relatively unimportant for ocean water and frequencies of the order of a megacycle and less. The theoretical solution for radio propagation over perfectly conducting spherical earth with atmospheric refraction is in agreement with available experimental data for propagation over ocean water for frequencies below a few megacycles. Eckersley´s extension of Watson´s solution to take into account the effect of the imperfect conductivity of the earth by the phase integral method is found to contain approximations which render its results questionable.