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. The analysis presented 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⩾10 MHz, the amplitude of an outgoing wave decreases much more rapidly than when f<10 MHz. This is true in the planar region when ρ_i<ρ<ρ_c , and throughout the spherical region ρ_s>ρ _c