Measurements of the phase of signals received over transmission paths with electrical lengths varying as a result of atmospheric turbulence

A system for the measurement of the variations in effective lengths of radio propagation paths is described. The observed path-length instabilities are considered to be caused by the same atmospheric turbulence responsible for the existence of VHF and UHF signals far beyond the radio horizon. Preliminary results obtained on 172.8 mc and 1046 mc along a 3-1/2 mile path are reported. It is pointed out that measurements of this type should provide a powerful tool for the study of the size and intensity of the refractivity variations of the atmosphere giving rise to the observed phenomena.