Duga-1 Antenna System, Chernobyl

Duga-1 was part of the Soviet Union early warning system for Air Based Missiles (ABM), forming part of an over-the-horizon radar (OTH) system. This site is sometimes called Duga-3 online, but that is seemingly incorrect. Built in the 1970s, it measures measure 479 feet tall and spans a nearly half a mile. The site was shrouded in secrecy during the height of the Cold War, and on official maps it was marked as a children’s summer camp.

Duga-1 was nicknamed “The Russian Woodpecker” due to the sharp, repetitive tapping noise of its broadcasts on shortwave radio bands between July 1976 and December 1989. NATO military intelligence code-named Duga-1 “Steel Yard” for their reports during the Cold War. It randomly changed frequency which disrupted legitimate broadcasts and amateur radio,  resulting in thousands of complaints by many countries worldwide during its years of operation.

The U.S. Federal Communications Commission (FCC) was investigating these signals Starting in the late 1980s, when the signals became less frequent, and in finally disappeared altogether in 1989.  No public announcement has been made to explain the shutdown of the Duga Antenna Systems.

Read more about Duga-1 on Wikipedia.