VLF Phase Delay Variability and the Design of Long Range Navigation Aids

摘要

A review is given of the experimentally determined characteristics of the propagation of VLF radio waves to great distances in the earth ionosphere waveguide, and these characteristics are examined in the light of waveguide mode theory. In particular the phase delay variations as a function of frequency, distance from transmitter, time of day, year, solar activity are discussed. Most of this experimental data refers to frequencies of 16 kHz and above, and detailed information on frequencies in the lower portion of the VLF band (10-14 kHz) has had to await the recent experimental OMEGA transmissions (1966 onwards). Included in the review are experimental data gathered during the past 12 months on OMEGA transmissions, and the role that the propagation data plays in the design of a navigation system such as OMEGA is brought out. (Author)