File:Early radar antenna - US Naval Research Laboratory Anacostia.jpg

Size of this preview: 464 × 600 pixels. Other resolutions: 186 × 240 pixels | 550 × 711 pixels.

Original file (550 × 711 pixels, file size: 101 KB, MIME type: image/jpeg)

This is a file from the Wikimedia Commons. Information from its description page there is shown below.
Commons is a freely licensed media file repository. You can help.

Summary

Description	English: Antenna of one of the first experimental US radars being developed during the late 1930s on the roof of the US Naval Research Laboratory, Anacostia, Washington DC. Operating at 200 MHz, it was the first rotating radar antenna. Research in radiolocation was started as early as 1922 by Naval radio engineers Albert Hoyt Taylor and Leo Clifford Young. In 1930 at the newly opened NRL, with another engineer Lawrence Hyland they began a research program. In 1934 they patented a radar system. This picture shows a "bedspring" antenna made of multiple dipole antennas which was needed to create a beam narrow enough to locate ships or planes. The antenna is mounted on a mast so it can rotate and also tilt to point up into the sky. The rotating mast extends through the roof to a large manual wheel in the room below which contains the radar equipment, so it can be rotated by hand. Caption: Closeup of the antenna of the first complete radar, installed "topside" of a building at the Naval Research Laboratory, Anacostia, D. C. in the late 1930s. It is a "dirigible" antenna, meaning that it is so mounted that it can be turned to allow for around the compass search
Date	October 1945
Source	Retrieved September 30, 2014 from "Radar: The Silent Weapon of World War 2" in Radio News magazine, Ziff-Davis Publishing Co., New York, Vol. 34, No. 4, October 1945, p. 30 on American Radio History site
Author	Unknown authorUnknown author
Permission (Reusing this file)	This 1945 issue of Radio News magazine would have the copyright renewed in 1973. Online page scans of the Catalog of Copyright Entries, published by the US Copyright Office can be found here. [1] Search of the Renewals for Periodicals for 1978 and later show no renewal entries for Radio News. Therefore the magazine's 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.

العربية ∙ Deutsch ∙ English ∙ español ∙ français ∙ galego ∙ italiano ∙ 日本語 ∙ 한국어 ∙ македонски ∙ português ∙ português do Brasil ∙ русский ∙ sicilianu ∙ slovenščina ∙ українська ∙ 简体中文 ∙ 繁體中文 ∙ +/−