The propagation time of a radio pulse

The propagation of the ground-wave pulse between points on the ground is of considerable practical importance, particularly in the application of the Loran-C navigation system to the absolute time synchronization of geographically separated clocks. Thus, the envelope of the pulse is frequently used to remove ambiguities which would otherwise result from the pulse synchronization at the characteristic or carrier frequency of the pulse. The propagation of the ground wave over finitely conducting ground modifies the propagation time of the tagged point-in-time on the envelope by amounts which may be sufficiently large as to cause cycle ambiguity radians at the carrier or characteristic frequency of the pulse. It is therefore the purpose of this paper to investigate the magnitude of this error by ascertaining the true signal velocity as determined by tagging a point-in-time on the leading edge of a groundwave pulse and calculating the time corrections for various ground conductivities and distances. These calculations can then be applied to resolve the radians ambiguity of the precision phase velocity instrumentation for Loran-C especially when the system is used for absolute-time synchronization.