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.

[1] 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.

[2] The unclaimed signal was a source of speculation, giving rise to theories such as Soviet brainwashing and weather modification experiments.

[3] This massive structure formed a phased array and was necessary in order to provide high gain at HF as well as facilitating beam-steering, though it is unconfirmed whether the latter was actually used in normal operation.

While the amateur radio community was well aware of the system, the OTH theory was not publicly confirmed until after the dissolution of the Soviet Union.

The first experimental system, Duga, was built outside Mykolaiv in Ukraine, successfully detecting rocket launches from Baikonur Cosmodrome at 2,500 kilometres (1,600 mi).

This was followed by the prototype Duga, built on the same site, which was able to track launches from the far east and submarines in the Pacific Ocean as the missiles flew towards Novaya Zemlya.

These signals even caused interference on 27 MHz CB radios in the late ’60s and early ’70s, sometimes completely blocking even local communications in Portugal, for example, leading to the supposition of several megawatts of RF power transmission.

[citation needed] Triangulation by amateur radio hobbyists and NATO showed the signals came from a location in present-day Ukraine, at the time called the Ukrainian Soviet Socialist Republic (part of the USSR).

[citation needed] A second installation was built near Komsomolsk-on-Amur, in Bolshya Kartel and Lian, but did not become active for some time.

[10][11][12] Even from the earliest reports it was suspected that the signals were tests of an over-the-horizon radar,[6] and this remained the most popular hypothesis during the Cold War.

When a second Woodpecker appeared, located in eastern Russia, but also pointed toward the US and covering blank spots in the first system's pattern, this conclusion became inescapable.

Although the reasons for the eventual shutdown of the Duga systems have not been made public, the changing strategic balance with the end of the Cold War in the late 1980s may have had a part to play.

Another factor perhaps was the success of the US-KS early-warning satellites, which began entering service in the early 1980s, and by this time had grown into a complete network.

According to some reports, the Komsomolsk-on-Amur installation in the Russian Far East was taken off combat alert duty in November 1989, and some of its equipment was subsequently scrapped.

], the radar appears permanently deactivated and will not likely receive future maintenance because such arrangements were not included as part of the 1992 Russian and Ukrainian talks; with regards to the Dnepr early warning radar systems at Mukachevo and Sevastopol, most of the antenna still stands and is often used by radio amateurs who visit the area using their own portable radio equipment.

[15][16] It was built outside the Black Sea port of Mykolaiv in southern Ukraine, and successfully detected rocket launches from Baikonur Cosmodrome about 2,500 kilometres (1,600 mi) away.

Markiyan Kamysh's book Stalking the Atomic City: Life Among the Decadent and the Depraved of Chornobyl depicts illegal trips to the Chernobyl Exclusion Zone, including to the Duga, and was praised by reviewers.

The film includes interviews with the commander of the duga, Vladimir Musiets, as well as the Vice-Commander, the Head of the Data Center, and others involved in building and operating the radar.

[20] The Duga radar is also featured in the films of the Divergent series, where it was used as the giant wall and fence surrounding the main city.

A Duga radar is featured in the 2017 game PUBG: Battlegrounds in a map which portrays a fictional Russian Military base.

The Chernobyl DLC for the game Spintires features a representation of the sarcophagus and an antenna array similar in appearance to Duga.