Para usar esta imagem numa página da Wikipédia inserir: [[Imagem:Log periodic VHF TV antenna 1963.jpg|thumb|180px|Legenda]]
Descrição do ficheiro
DescriçãoLog periodic VHF TV antenna 1963.jpg
English: Early log-periodictelevision antenna used on the VHF TV channels 2-13, 54 - 216 MHz, from 1963. It consists of 11 dipoledriven 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.
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.
Licenciamento
Public domainPublic domainfalsefalse
Este trabalho está em domínio público porque foi publicado nos Estados Unidos entre 1929 e 1963, com um aviso de direito autoral, e seu direito autoral não foi renovado. A menos que seu autor esteja morto por vários anos, não é do domínio público nos países ou áreas que não se aplica a regra do curto prazo para as obras dos E.U.A, como o Canadá (70 apm), China (50 apm, com exceção de Hong Kong e Macau), Alemanha (70 apm), México (100 apm), Suíça (70 apm), e de outros países com tratados individuais. Veja Commons:Hirtle chart para maiores explicações.