Woodpecker The Russian Duga 3 First heard in 1976, it continued for ten years. Named after its readily identifiable repetitive tapping note. It used an high-power signal estimated at around 10 Megawatts. It continually switched between shortwave frequencies and caused disruption to other broadcasts. Post the Cold War it was confirmed that the strange signal originated from an over-the-horizon (OTH) radar as part of the Soviet Anti Ballistic Missile early warning system. The Soviet Duga-3 OTH system is located in Chernobyl (now Ukraine). Transmitter was codenamed Steel Yard by Western military intelligence. (A sound recording of this can be found on our Cold War Signals page).

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