Electromagnetic ground-wave field of vertical antennas

Communication between the shore and a ship and between ships makes use of frequencies from 1 to 30 MHz. Distances up to 10000 km are involved. The analysis presented in this paper provides new simple formulas for the ground wave along the surface of the sea. These include not only the range in which the surface of the sea is well approximated by a plane but also the range where accurate account must be taken of the curvature of the spherical earth. Of practical significance is the fact that when f/spl ges/10 MHz, the amplitude of an outgoing wave decreases much more rapidly than when f<10 MHz.