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 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, its name no relationship a 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. 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 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 -- their codename in the USSR -- were installed all over the Soviet Union and allied countries before the U.S. military became interested and developed their own versions of the technology. Curiously, several Krug arrays were installed as pairs within less than 10 km kilometers of each other. At least three Krug arrays were installed near Moscow just to the north, east and south of the city.
The first Wullenweber array 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 and studied the array and researched the physics of HF/DF under contract to the U.S. Navy from 1947 through 1960. Records of his research are in the university 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 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 clearly visible in high resolution aerial photography posted on the internet.
In the early 1960s, the U.S. Navy deployed a worldwide network of fourteen AN/FRD-10 arrays 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 arrays were installed in 1970-71 by the Canadian Forces in Gander, Newfoundland and Masset, British Columbia. As of 2007, fourteen of the 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 in Mountain View, CA (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. Installation of the first two systems was 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.
A second contract was awarded to Sylvania to build 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 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 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 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 Udon Thani array was dismantled in 1975 following base closure. The Augsburg array was turned over to the Bundesnachrichtendienst -- the German Intelligence Service -- in 1998, and it is no longer believed to be in service.
In the 1970s, the British developed a smaller, more economical CDAA array codenamed Pusher. At least 20 Pusher arrays 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.
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External links
Aerial photos of Krug and Wullenweber arrays]