Institute for Telecommunication Sciences / December 1964

December 1964: First Description of VLF Propagation Published

Dr. James Wait and Kenneth Spies of the Central Radio Propagation Laboratory (CRPL) published NBS Technical Note 300 on December 30, 1964. “Characteristics of the earth-ionosphere waveguide for VLF radio waves” was an important contribution to understanding radio propagation in the Very Long Frequency (VLF) range between 8kc/s and 30kc/s (3–30 kHz). It was the first description of how VLF waves propagate in the space between the Earth and the ionosphere. Using a man-made waveguide which directs radio waves as a model of the atmosphere, Wait and Spies described the natural phenomenon in simple terms. Today, VLF signals are used for some data (including radio clocks) and navigation services. In 1964, CRPL was investigating VLF for submarine communication, a VLF use that continues today. Tech Note 300 was notable not only for the concepts it described, but because it was the first publication to present the propagation algorithms to describe the behavior of radio waves trapped between the Earth and the ionosphere. The graphical and numerical results in Tech. Note 300 were the only representation of these propagation phenomena available for many years, and were extensively relied upon by researchers of the time. ITS researchers follow in the footsteps of Wait and Spies by investigating and characterizing the propagation of radio waves in all frequencies for improved communications.