Duga radar

Duga was a Soviet over-the-horizon radar system used as part of the Soviet missile defense early-warning radar network. The system operated from July 1976 to December 1989. Two operational Duga radars were deployed, one near Chernobyl and Chernihiv in the Ukrainian SSR, the other in eastern Siberia.

The Duga systems were extremely powerful, over 10 MW in some cases, and broadcast in the shortwave radio bands. They appeared without warning, sounding like a sharp, repetitive tapping noise at 10 Hz repetition rate, which led to it being nicknamed by shortwave listeners the Russian Woodpecker. The random frequency hops disrupted legitimate broadcasts, amateur radio operations, oceanic commercial aviation communications, and utility transmissions, resulting in thousands of complaints by many countries worldwide.