The Wullenweber is a type of Circular 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 the occasional maritime rescue. The antenna is colloquially known as the elephant cage. "Wullenweber" was a cover term the used to identify the German World War II development program, it has no relationship to the people involved in the German 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 of the system 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. Pietzner, Dr. Schelhorse, and Dr. Wächtler. The latter was a co-founder of Plath Co and later a consultant to Plath and Telefunken (electronic companies). Although all men retired in West Germany, some of their second-echelon technicians were taken to the USSR after the war. This led to the Soviets deploying 20 CDAAs before the United States military became interested and developed their own version of the technology.
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 CDAA and studied the array and researched the physics of HF/DF under contract to the U.S. Navy from 1947 through 1960. Hayden led the design and development of a very large Wullenweber array at the university's Bondville Road Field Station, a few miles southwest of Bondville, IL. The array consisted of 120 vertical monopoles covering 2-20 MHz. Tall wooden 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 (88.37983W, 40.04982N) and all other post-war Wullenweber arrays are still clearly visible in aerial photography posted on the internet.
In the early 1960s, the U.S. Navy deployed a worldwide network of 14 AN/FRD-10 direction finders based on lessons learned from the Bondville experimental array. Two additional arrays were installed at Sugar Grove, WV for naval HF communications (not direction finding), and two additional AN/FRD-10 direction finders were installed in 1970-71 by the Canadian Forces in Gander, Newfoundland and Masset, British Columbia. As of 2007, only the two Canadian AN/FRD-10 arrays remain in use.
In 1959 the first contract to build the next generation Wullenweber array -- AN/FLR-9 antenna receiving system -- was awarded by the U.S. Air Force to the Sylvania Corporation (now General Dynamics Advanced Information Systems). The contract called for the completion of two AN/FLR-9 systems at San Vito dei Normanni Air Station, Italy and RAF Chicksands, United Kingdom. Both were completed in 1962. The San Vito array was dismantled following base closure in 1993 and the Chicksands array was dismantled following base closure in 1996.
Following the completion of these CDAAs, a second contract was awarded to Sylvania to build Wullenwebers at Misawa AB, Japan and Clark AB, Philippine Islands; one in Pakistan (never built), one at Elmendorf AFB, Alaska, and one at Karamursel AS, Turkey. The last two were completed in 1966. The Karamursel array was dismantled in 1977 following a conflict over foreign aid to Greece. The Clark AB array was decommissioned immediately after the Mt. Pinatubo volcano eruption in 1991. As of 2007, only the Elmendorf and Misawa arrays remain in service, but 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 two AN/FLR-9s; one at USASA Field Station Augsburg, Germany and one at Udon Thani, Thailand. Both were completed in 1970. The Army's version of the AN/FLR-9 has the same antenna 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 Augsburg array was turned over to the German Intelligence Service (BND) in 1998, and it is no longer believed to be in service. The Udon Thani array was dismantled in 1975 following base closure.
In the 1970s, the British developed a smaller, more economical CDAA antenna (but not a Wullenweber) codenamed Pusher. The Pusher array is used primarily by the British, Canadians and their allies. In the U.S. military, this array is known as the AN/FRD-13.