World's Longest Radio Antenna
January 1967 Popular Science

January 1967 Popular Science [Table of Contents] Wax nostalgic about and learn from the history of early electronics. See articles from Popular Science, published 1872-2021. All copyrights hereby acknowledged.

This little news item appeared in the "PS Readers Talk Back" section of the January 1967 issue of Popular Science magazine. It was submitted by Ronald L. Sefton, the Station Scientific Leader at Byrd Station, Antarctica. He wrote to challenge a piece in an earlier edition of the magazine which claimed another entity had the world's longest radio antenna. According to Mr. Sefton, his outfit had both 21-mile-long and a 10-line-long VLF dipole antennas erected for experimental communications. An amazing paper titled "University of Washington Research Program in Antarctica, 1965-1966,"  on the VLF Longwire system is available. It shows the antenna configuration used for the ionospheric studies which included sporadic E measurements. It would be interesting to know how the curvature of the Earth over that distance affected the radiation pattern. A wire dipole supported above the ground at end point would exhibit a catenary shape (hyperbolic cosine - cosh) curving downward in the center, but the wire lying on the curved Earth would be more circular and curving upward in the center. For a dipole antenna to resonate at its fundamental frequency, its length is typically half the wavelength of the signal. At a length of 21 miles, the corresponding wavelength would be 42 miles. This translates to a frequency of about 4.4 kHz. In practice, this frequency is within the VLF range (3 - 30 kHz) and aligns with applications of such antennas for scientific research.

PS Readers Talk Back: World's Longest Radio Antenna

We at Byrd Station take exception to the description of the world's longest radio antenna (two miles) in "Science Newsfront" [July]. Two antennas here are considerably longer. One is a 21-mile dipole, the other is a 10-mile dipole oriented at right angles to the longer antenna. The antennas were placed on the snow surface approximately 8,000 feet above the earth's surface. This places them at an effective height of around 2,000 feet when the dielectric properties of the snow and ice are considered.

At present the installation is being used by the University of Washington and Stanford University for geophysical research.

Ronald L. Sefton, Station Scientific Leader, Byrd Station, Antarctica.