My wife and I just visited a unusual attraction in Thailand, a former US signals intelligence HF direction finding station used during the Vietnam war and commonly referred to as an "Elephant cage".
But first a background. This is a huge facility. The AN/FLR-9 Antenna was a large circular array built at 8 locations during the Cold War. Collectively the 8 stations could locate and intercept HF communications anywhere on the planet, an individual station had accurate direction finding up to 7,400 km away.
The antennae was gigantic, consisting of three concentric rings with outer ring 440 metres in diameter. The antenna two outer rings were supported by 96 pillars of 40 metre height.
In Thailand an "Elephant cage" was built in 1970 at the tiny village of Non Sung, about 15 km south of Udon Thani in the north East region. Operated by the 7th RRFS (rather blandly described as a "Radio Research Field Station") it was really a top secret intell gathering station under the command of the Army Security Agency. In fact the 7th RRFS had been operating there since 1967. By 1970 the station had a 1,000 linguists, O5H (high speed morse intercept operators), cryptologists and communication staff. The development of the 320 acre site (which cost the US $400 to buy) cost US$50 million. Primarily purpose was listening in to NVA and Viet Cong radio traffic and monitor Chinese military movements.
But political wind changes saw the Thai Government asking the US to close the Station in 1976, and it remained of limits to civilians until September 2018 when the Thai Army opened the Ramasun Historical museum.
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