Wullenweber The Wullenweber ( the original name introduced by Dr . Hans Rindfleisch was Wullenwever ) 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 for radio direction finding . It was used by the military to triangulate radio signals for radio navigation , intelligence gathering and search and rescue . Because its huge circular reflecting screen looks like a circular fence , the antenna has been colloquially referred to as the " elephant cage . " The term " wullenwever " was the World War II German cover term used to identify their secret CDAA research and development program ; its name is unrelated to any person involved in the program . History . Wullenweber technology was developed by the German navy communication research command , Nachrichtenmittelversuchskommando ( NVK ) and Telefunken during the early years of World War II . The inventor was NVK 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 . Hans Schellhoss , and Dr . Maximilian Wächtler . The latter was a founder of Plath GmbH in 1954 and later a consultant to both Plath and Telefunken . Dr . Rolf Wundt , a German antenna researcher , 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 1947 on the same ship as Wernher Von Braun and his wife and parents . He was first employed by the U . S . Air Force , then by GT & E Sylvania Electronics Systems on Wullenweber and other antenna projects . 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 ( 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 kilometers of each other , apparently for radio navigation purposes . At least four Krugs were installed near Moscow ; just to the north , east and south ( ) of the city . The Krugs were used to track the early Sputnik satellites , using their 10 and 20 MHz beacons , and were instrumental in locating re - entry vehicles . The first Wullenwever was built during the war at Skisby ( in German : Hjörring ) , Denmark ( ) . It used forty vertical radiator elements , placed on the arc of a circle with a diameter of 120 meters . Forty reflecting elements were installed behind the radiator elements , suspended on a circular wooden support structure with a diameter of 112 . 5 meters . To more easily obtain true geographic bearings , the north and south elements were placed exactly on the North - South meridian . The Soviet Krug arrays also use the 40 radiator Wullenwever configuration . The array in Skisby was extensively studied by the British , then destroyed following the war in accordance with the Geneva Convention . Dr . 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 . 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 was later employed by Southwest Research Institute where he continued to contribute to HF direction finding technology . 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 circular screen of vertical wires located within the ring of monopoles . Due to their immense size , the location of the Bondville array ( ) and the other post - war Wullenweber arrays are clearly visible in high resolution aerial photography available on the internet . In 1959 , the U . S . Navy contracted with ITT Federal Systems to deploy a worldwide network of AN / FRD - 10 HF / DF arrays based on lessons learned from the Bondville experimental array . The FRD - 10 at NSGA Hanza , Okinawa was the first installed , in 1962 , followed by eleven additional arrays , with the last completed in 1964 at NRRF Imperial Beach , CA . ( Silver Strand ) A pair of FRD - 10s not equipped for HF / DF were installed in 1969 at NAVRADSTA ( R ) Sugar Grove , WV for naval HF communications , replacing the NSS receiver site at the Naval Communications Station in Cheltenham , MD . The last two FRD - 10 HF / DF arrays were installed in 1971 for the Canadian Forces in Gander , Newfoundland and Masset , British Columbia . After the Hanza array was decommissioned in 2006 , the Canadians now operate the last two FRD - 10 arrays in existence . Also in 1959 , a contract to build a larger 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 ( ) in the 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 Camp Ramasun in Udon Thani Province , 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 " Lumped Constant " delay line design and the Air Force used a " Coaxial " delay line design . The Camp Ramasun 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 , similar to the FRD - 10 , at Chitose and Miho . Later in the 1970s , Plessey — now Roke Manor Research Limited — 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 . Today , the Strategic Reconnaissance Command of the German Armed Forces operates a wullenweber array in Bramstedtlund with a diameter of 410m as one of its three stationary Sigint battalions .