Tuesday, August 11, 2015

Radio Inside the Elephant Cage

Wullenweber was a code name. In and of itself the word meant nothing. Originally spelled "Wullenwever"which was a Germanic surname. Jürgen Wullenwever was probably the most famous of the clan, was burgomaster of Lübeck Germany from 1533 to 1535. The aristocrats rose to power in 1535 and Jürgen was beheaded. His connection to the Wullenweber is highly dubious.

Wullenweber German code word used to identify secret Circularly Disposed Antenna Array (CDAA) research and development program. The name was probably selected by Dr. Hans Rindfleisch. The CDAA is a large circular antenna array used for radio direction finding. It was used by the military to triangulate radio signals. This can be used for things like navigation, search and rescue, but also search and destroy. the nickname "Elephant cage" for the antenna probably comes from a AN/FLR-9 Wullenweber installation at RAF Chicksands near Bedfordshire England. But the name may go all the way back to Illinois. More here.

Wherever it was first used, the metaphor makes sense. The Wullenweber antennas were ten stories tall and one thousand feet across. Its huge circular reflecting screen looks like a circular fence tall enough to contain even an elephant. One hopes that Rindfleisch had a sense of humor. CDAA technology was developed by the German Naval Communication Research Command and Telefunken. It's sounds more intimidating in German:  Nachrichtenmittelversuchskommando (NVK.) Many of the German engineers and scientists like Dr. Rolf Wundt,were taken to the U.S. by the Army after the war under Operation Paperclip. For the U.S. Military they continued to work on projects derived from Wullenweber technology.  Strangely the U.S. Dawdles on the project and even with less senior technicians, the USSR began building CDAA antennas as early as 1950. At least 30 "Krug" arrays were built in Russia and western Europe to listen to the West.

The Germans built the first Wullenwever at Skibsby, near the city of Hjørring. It used forty vertical radiator elements, placed on the arc of a circle with a diameter of 120 meters. The later Soviet Krug arrays derived their designs from this model and also use a 40 vertical radiator configuration. The array in Skibsby was studied by the British, then destroyed following the war per the Geneva Convention. A second array was built at Langenargen, also in Germany but this was disassembled and brought back to the U.S.  and reassembled at Bondville Road Field Station, near Bondville, IL under the supervision of Professor Edgar Hayden from the University of Illinois. The impressive performance of the Wullenwever led the Navy start building a global network of CDAA antennas in 1959.

One AN/FRD-9 was built in Richardson, Alaska, another in Clark AFB, Philippines another in Karamursel, Turkey, more in Thailand, Italy and Japan. Two AN/FRD-10 systems were installed in Canada, One in Okinowa, another at Imperial Beach, CA. A pair of FRD-10s were also constructed in 1969 at a Naval Radio Station in Sugar Grove, WV. A third and smaller variant, the AN/FRD-13 continued to be built into the 1970s. As of 1024 the last operating Wullenweber was the one in Richardson, Alaska. The cold war is over and spying is easier today than ever. They just wait for you to install Windows 10. More here.