Wullenweber
From Wikipedia, the free encyclopedia
The Wullenweber is a type of Circularly Disposed Antenna Array (CDAA) sometimes referred to as a Circularly Disposed Dipole Array (CDDA). It is a large circular antenna array used by the military to triangulate radio signals for intelligence gathering and search and rescue. The antenna is colloquially known as the elephant cage. "Wullenweber" was the World War II German cover term used to identify their CDAA research and development program, its name is unrelated to any person involved in the program.
CDAA technology was developed by the German navy signal intelligence research and development center (Nachrichtenversuchsanstalt der Marine NVA) during the early years of World War II. The inventor was NVA group leader Dr. Hans Rindfleisch, who worked after the war as a Technical Director for the northern Germany official broadcast (Norddeutscher Rundfunk - NDR). Technical team leaders were Dr. Joachim Pietzner, Dr. Schelhorse, and Dr. Maximilian Wächtler. The latter was a founder of Plath GmbH in 1954 and later a consultant to Plath and Telefunken.
Although the three men retired in West Germany, some of their second-echelon technicians were taken to the USSR after the war. At least 30 Krug arrays -- the cover term for the Soviet CDAA program -- were installed all over the Soviet Union and allied countries before the U.S. military became interested and developed their own CDAAs. Curiously, several Krugs were installed as pairs within less than 10 km kilometers of each other. At least four Krugs were installed near Moscow; just to the north, east and south of the city.
The first Wullenweber was built during the war at Joring, Denmark; however, it was destroyed following the war in accordance with the Geneva Convention. Dr. Wachtler arranged to have a second array built, at Telefunken expense, at Langenargen/Bodensee, for further experiments 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.
Professor Edgar Hayden, then a young engineer in the 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. Navy from 1947 through 1960. 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 led the design and development of a large Wullenweber array at the university's Bondville Road Field Station, a few miles southwest of Bondville, IL. The array consisted of a ring 120 vertical monopoles covering 2-20 MHz. Tall wood poles supported a 1000 foot diameter circular screen of vertical wires located within the ring of monopoles. Due to their immense size, the locations of the Bondville array and all other post-war Wullenweber arrays are clearly visible in high resolution aerial photography available on the internet.
In the early 1960s, the U.S. Navy contracted with ITT Federal Systems to deploy a worldwide network of sixteen AN/FRD-10 CDAA arrays based on lessons learned from the Bondville experimental array. Two arrays were installed at Sugar Grove, WV for naval HF communications (not direction finding) in 1969, and arrays were installed in 1971 for the Canadian Forces in Gander, Newfoundland and Masset, British Columbia. As of 2007, fourteen AN/FRD-10 arrays have been decommissioned, only the Canadian arrays remain in service.
In 1959 the first contract to build the next generation Wullenweber array -- the AN/FLR-9 antenna receiving system -- was awarded by the U.S. Air Force to GT&E Sylvania Electronics Systems (now General Dynamics Advanced Information Systems). The first FLR-9 was installed at RAF Chicksands , United Kingdom in 1962. The second FLR-9 was installed at San Vito dei Normanni Air Station, Italy also in 1962. The Chicksands array was dismantled following base closure in 1996 and the San Vito array was dismantled following base closure in 1993.
A second contract was awarded to Sylvania to install AN/FLR-9 systems at Misawa AB, Japan; Clark AB, Philippine Islands; Pakistan (never built); Elmendorf AFB, Alaska; and Karamursel AS, Turkey. The last two were completed in 1966. The Karamursel AS was closed and array was dismantled in 1977 in retribution for the suspension of U.S. military aid to Turkey. The Clark AB array was decommissioned after the Mt. Pinatubo volcano eruption in 1991. It was later converted into an outdoor amphitheater. As of 2007, only the Elmendorf and Misawa arrays remain in service, but both are likely to be decommissioned soon due to their age and unavailability of repair parts.
The U.S. Army awarded a contract in 1968 to F&M Systems to build AN/FLR-9 systems for USASA Field Station Augsburg, Germany and Udon Thani, Thailand. Both were installed in 1970. The Army version has the same design as the Air Force version, but the design of the delay lines in the Beam Forming Networks inside the Central Building are different. The Army used what is called a "Lamp Cluster" delay line design and the Air Force used a "Coaxial" delay line design. The Udon Thani array was dismantled in 1975 following base closure. The Augsburg array was turned over to the Bundesnachrichtendienst -- the German Intelligence Service known as the BND -- in 1998, and it is no longer believed to be in service.
During the 1970s, the Japanese government installed two large Wullenweber arrays at Chitose and Miho.
Later in the 1970s, the Plessey company of Great Britain developed their smaller, more economical Pusher CDAA array. At least 25 Pusher CDAAs were installed in many countries around the world. Several Pusher arrays were installed in U.S. military facilities, where the array is known as the AN/FRD-13.
