Circularly disposed antenna array: Difference between revisions

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{{More citations needed|article|date=October 2016}}

[[File:NSGA Galeta Island Site.jpg|thumb|Direction-finding system [[Galeta Island (Panama)|Galeta Island]], [[Panama]] ]]

A '''circularly disposed antenna array (CDAA)''', sometimes referred to as a '''circularly disposed dipole array (CDDA)''' or a '''''wullenweber''''',<ref>the original name introduced by Dr. Hans Rindfleisch was Wullenwe'''v'''er</ref> is a large circular [[antenna (radio)|antenna]] array used for [[radio direction finding]]. They are used by military and government agencies to [[Triangulation|triangulate]] radio signals for radio navigation, intelligence gathering, search and rescue, and enforcement of broadcasting laws. Because their huge circular reflecting screens lookslook like circular fences, some antennas have been colloquially referred to as "''elephant cages''". The term "''wullenwever''" was the World War II German [[Code name|cover term]] used to identify their secret CDAA research and development program; its name is unrelated to any person involved in the program.

Many such CDAA systems are used by many nations, such as the former [[Soviet Union]] and modern-day [[Russia]], [[Germany]], the [[United Kingdom]], and the [[United States]].

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===Post-war development===

Although Pietzner, Schellhoss, and Wächtler retired in West Germany, some of their second-echelon technicians were taken to the [[USSR]] after the war. At least 30&nbsp;Krug (Russian for circle) arrays were installed all over the Soviet Union and allied countries in the 1950s, well before the U.S. military became interested and developed their own CDAAs. Several Krugs were installed in pairs less than 10&nbsp; kilometers offrom each other, apparently for radio navigation purposes. At least four Krugs were installed near Moscow; just to the north, east and south ({{coord|55.46408|N|37.3698|E|scale:10000}}) of the city. The Krugs were used to track the early Sputnik satellites, using their 10 and 20&nbsp;MHz beacons, and were instrumental in locating re-entry vehicles. The Soviet Krug arrays also use the 40-element CDAA configuration.

The array in Skibsby was extensively studied by the British, and then destroyed following the war in accordance with the Geneva Convention. Dr.&nbsp;Wächtler arranged to have a second array built, at Telefunken expense, at Langenargen/Bodensee, for further experimentation after the war. In the years following the war, the U.S. disassembled the Langenargen / Bodensee array and brought it back to the U.S., where it became known as the "''Wullenweber''" array.

One of the German antenna researchers, Dr.&nbsp;Rolf Wundt, was one of hundreds of German scientists taken to the U.S. by the Army after the war under [[Operation Paperclip]]. He arrived in New York in March&nbsp;1947 on the same ship as [[Wernher Von Braun]] and his wife and parents. He was first employed by the U.S.&nbsp;Air Force, thenand bythen GT&E&nbsp;Sylvania Electronics Systems on CDAA and other antenna projects.

Professor Edgar Hayden, then a young engineer in the [[University of Illinois at Urbana-Champaign|University of Illinois]] Radio Direction Finding Research Group, led the reassembly of the ''Wullenweber'', studied the design and performance of [[HF/DF]] arrays and researched the physics of HF/DF under contract to the U.S.&nbsp;Navy from 1947 through 1960.

Hayden led the design and development of a large circularly disposed array at the university's Bondville Road Field Station, a few miles southwest of Bondville, IL. The array consisted of a ring of 120&nbsp;vertical monopoles covering 2–20&nbsp;MHz. Tall wood poles supported a {{convert|1000|ft|m|adj=mid|&nbsp;diameter}} circular screen of vertical wires located within the ring of monopoles. His research is still used today to guide the design and site selection of [[HF/DF]] arrays. Records of his research are available in the university's archives. Hayden was later employed by [[Southwest Research Institute]] where he continued to contribute to HF direction finding technology.

===The 1960s–1970s construction boom and subsequent demolition===

In 1959, the U.S. Navy contracted with [[ITT Corporation|ITT]] Federal Systems to deploy a worldwide network of [[AN/FRD-10]] HF/DF arrays based on lessons learned from the Bondville experimental array.