Circularly disposed antenna array

CDAA technology was developed by the German navy communication research command, Nachrichtenmittelversuchskommando (NVK) and Telefunken, working on the Wullenweber 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)).

The first Wullenwever was built during the war at Skibsby, north-east of the city of Hjørring (in German: Hjörring), Denmark (57°29′10″N 10°00′38″E / 57.48611°N 10.01056°E / 57.48611; 10.01056).

Although Pietzner, Schellhoss, and Wächtler 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 CDAAs.

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.

Tall wood poles supported a 1,000-foot  diameter (300 m) circular screen of vertical wires located within the ring of monopoles.

Hayden was later employed by Southwest Research Institute where he continued to contribute to HF direction finding technology.

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.

Later in the 1970s, Plessey (now Roke Manor Research Limited) of the United Kingdom developed the smaller, more economical Pusher CDAA array.

Therefore, it is believed to be still in service being used by BND and NSA as part of a larger complex of combined informational technology.

the Strategic Reconnaissance Command of the German Armed Forces operates a circularly disposed array in Bramstedtlund with a diameter of 410 metres (1,350 ft) as one of its three stationary Sigint battalions.