NSGA Imperial Beach AN/FRD-10 HF/DF Array

USA / California / Imperial Beach /
 military, antenna, abandoned / shut down
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There were sixteen AN/FRD-10 high-frequency direction-finding arrays built by the United States and Canada during the 1960s and 1970s. These sixteen stations, along with a number of Pusher HF/DF arrays, comprised the US Naval Security Group's BULLSEYE HFDF net. Pushers was simply the name given to simpler CDAAs.

The arrays operated in the range of 2 to 32 MHz. Their function was to detect, monitor, and plot the location of Soviet submarines and other radio emitters in the Atlantic and Pacific oceans. The largest array was some 260 m in diameter, 36 m high, and sat on a ground plane of 390 m diameter, with a two storey building at its centre, housing the main equipment and operators.

Naval Security Group Activity San Diego's history began on May 20, 1920, when the Secretary of the Navy authorized a Navy Radio Compass Station to provide navigational aid at Imperial Beach. In 1932, the unit was renamed Navy Direction Finder Station, and in 1940, a permanent Direction Finding (DF) station was established on the Coronado Strand Military Reservation.

By 1953, the station known as Naval Radio Receiving Station Imperial Beach became the Naval Security Group Department of Naval Communication Station San Diego. In 1965, the Wullenweber Circular Display Antenna Array, the last built, was commissioned at Imperial Beach. Finally, in 1998, Naval Security Group Activity San Diego was commissioned. The array was closed 30 Sep 1999.

www.navycthistory.com/Imperial_beach_intro.html
www.niocsd.navy.mil/history.htm
luxexumbra.blogspot.com/2005/06/frd-10-endangered-speci...
Wikipedia article: http://en.wikipedia.org/wiki/Wullenweber
Nearby cities:
Coordinates:   32°35'36"N   117°7'44"W

Comments

  • for communicating with submarines via ultra low frequency transmissions.
  • It is actually a VLF antenna array. Due to the long wavelength of Very Low Frequencies an long antenna is required hence the array looks so large.
  • It is a nonoperational High Frequency Direction Finding site. It has a Circularly Disposed Antenna Array originally designed to locate radio signals from 2 to 30 MHz. For more info and history, visit http://www.navycthistory.com/Imperial_beach_intro.html
  • The antenna type is a "Wallenwebber" and has been removed from service. It will be demolished when funds become available, kinda sad really.
  • Bob and Former Squid are correct: this was a HFDF Wullenweber array (aka "Elephant Cage"). The array was for receiving signals in the 2-30Mhz range. For another example, check out the Wullenweber array at Northwest: http://www.wikimapia.org/#lat=36.549673&lon=-76.258121&z=17&l=0&m=a&v=2
  • This array was part of the ECHELON network set up by the NSA and run by the US Navy. (The US Army and Air Force had their own installations). It was used to intercept HF communications from Soviet naval activity in the Pacific. It could also be used as a direction finding array. Of course it would only provide one vector indicating the direction from Imperial Beach. So at least two other vectors were required to pin point the location of the target. Those vectors would come from similar installations in northern California and near Seattle Washington. (or from the Canadian intercept site near Vancouver or from Elmendorf AFB in Alaska.)
  • Dismantling of this antenna began February 2105.
  • I WORKED THERE 1969 AND 70.WE ALL GOT A MEDAL FOR OUR STATION DEBRIEFING THE PUEBLO CREW
  • Interesting! I was there as an O Brancher from 68 to 70. Chief Sanders, George Ferriea, Larry Goematt. I was known a Frank Trumble and later went to NavCommStaPhil
  • This was not a VLF antenna. I work there from 1986 to 1989 and part of that time I was the LPO of the HFDF shop. This is a Wullenweber antenna AN/FRD-10 and was used to provide High Frequency Direction Finding in the 2-30MHZ range.
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This article was last modified 7 years ago