The propagation of l.f. and v.l.f. radio waves with reference to some systems applications

An outline is presented of the theoretical methods available for determining the propagation characteristics of v.l.f. and l.f. waves for both long and short transmission paths. Attention is drawn to the differences between the ray-hop and wave guide mode theories which have been applied to these frequency bands. The experimental study of v.l.f./l.f. propagation is discussed and the variations in the phase and amplitude of the received signals during normal and disturbed conditions are described. A comparison is made between the experimental results and those predicted from theoretical considerations. Some examples are given of the application of v.l.f./l.f. waves to navigation (mainly Omega) and to communications.