File:Log periodic VHF TV antenna 1963.jpg

Summary

DescriptionLog periodic VHF TV antenna 1963.jpg	Early log-periodic television antenna used on the VHF TV channels 2-13, 54 - 216 MHz, from 1963. It consists of 11 dipole driven elements of gradually decreasing length, each consisting of a pair of aluminum rods. The dipoles are mounted in a line, attached to the feedline to the TV in parallel, with alternating phase. The log-periodic dipole antenna was developed by R. H. Du Hamel and Paul Mayes at the University of Illinois.around 1962 and immediately became popular as a rooftop television antenna. Previous high-gain rooftop antennas for fringe TV reception were based on the Yagi-Uda antenna. The Yagi has an inherently narrow bandwidth and could not cover the entire VHF band with flat gain. The log-periodic antenna was unique in that it could achieve as high gain as the Yagi over a broad bandwidth, and so could cover the entire VHF-TV band. Log-periodic antennas for VHF TV reception had V-shaped elements, as shown in this antenna. This was because on the high channels the dipoles resonated at their 3rd harmonic; they functioned as 3/2 wavelength dipoles. At these frequencies the main lobe of the radiation pattern of each element splits into two lobes at an angle to the rod axis. Slanting the two sides of the dipole in a V shape caused the main lobes of both sides to combine into one lobe, increasing the gain on the high channels.
Date	June 1963
Source	Retrieved July 5, 2015 from Edward Finkel, "Log Periodic V" in Radio-Electronics magazine, Gernsback Publications, Inc., New York, Vol. 34, No. 6, June 1963, p. 24 on http://www.americanradiohistory.com archive
Author	Edward Finkel
Permission (Reusing this file)	This 1963 issue of Radio-Electronics magazine would have the copyright renewed in 1991. Online page scans of the Catalog of Copyright Entries, published by the US Copyright Office can be found here. Search of the Renewals for Periodicals for 1990, 1991, and 1992 show no renewal entries for Radio-Electronics. Therefore the copyright was not renewed and it is in the public domain.

Licensing

This work is in the public domain because it was published in the United States between 1929 and 1963, and although there may or may not have been a copyright notice, the copyright was not renewed. For further explanation, see Commons:Hirtle chart and the copyright renewal logs. Note that it may still be copyrighted in jurisdictions that do not apply the rule of the shorter term for US works (depending on the date of the author's death), such as Canada (70 years p.m.a.), Mainland China (50 years p.m.a., not Hong Kong or Macao), Germany (70 years p.m.a.), Mexico (100 years p.m.a.), Switzerland (70 years p.m.a.), and other countries with individual treaties.

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