Duga radar

Duga (Russian: Дуга, lit. 'arc' or 'curve') was an over-the-horizon radar (OTH) system used in the Soviet Union as part of its early-warning radar network for missile defence. It operated from July 1976 to December 1989. Two operational Duga radars were deployed, with one near Chernobyl and Liubech in the Ukrainian SSR, and the other in eastern Siberia. The Duga system was extremely powerful, reaching over 10 MW, and emitted in the shortwave radio bands. It was given the nickname Russian Woodpecker by shortwave listeners for its emissions randomly appearing and sounding like sharp, repetitive tapping noises at a frequency of 10 Hz. The random frequency hops often disrupted legitimate broadcasts, amateur radio operations, oceanic, commercial, aviation communications, and utility transmissions, resulting in thousands of complaints from many countries worldwide. The signal became such a nuisance that some communications receivers began including "Woodpecker Blankers" in their circuit designs. The unclaimed signal used to be a source of speculation, giving rise to theories such as Soviet brainwashing and weather modification experiments. However, because of its distinctive transmission pattern, many experts and amateur radio hobbyists realized it was an over-the-horizon radar system. NATO military intelligence had already given it the reporting name STEEL WORK or STEEL YARD, based on the massive size of the antenna, which spanned 700 metres (2,300 ft; 0.43 mi) in length and 150 metres (490 ft) in height.