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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.
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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 entitled "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.
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