''Duga'' (, ) was an

over-the-horizon radar Over-the-horizon radar (OTH), sometimes called beyond the horizon radar (BTH), is a type of radar system with the ability to detect targets at very long ranges, typically hundreds to thousands of kilometres, beyond the radar horizon, which is t ...

(OTH) system used in the

Soviet Union The Union of Soviet Socialist Republics. (USSR), commonly known as the Soviet Union, was a List of former transcontinental countries#Since 1700, transcontinental country that spanned much of Eurasia from 1922 until Dissolution of the Soviet ...

as part of its

early-warning radar An early-warning radar is any radar system used primarily for the long-range detection of its targets, i.e., allowing defences to be alerted as ''early'' as possible before the intruder reaches its target, giving the air defences the maximum tim ...

network for

missile defense Missile defense is a system, weapon, or technology involved in the detection, tracking, interception, and also the destruction of attacking missiles. Conceived as a defense against nuclear weapon, nuclear-armed intercontinental ballistic mi ...

. It operated from July 1976 to December 1989. Two operational ''duga'' radars were deployed, with one near

Chernobyl Chernobyl, officially called Chornobyl, is a partially abandoned city in Vyshhorod Raion, Kyiv Oblast, Ukraine. It is located within the Chernobyl Exclusion Zone, to the north of Kyiv and to the southwest of Gomel in neighbouring Belarus. ...

and

Liubech Liubech ( Ukrainian and Russian: ; ) is a rural settlement in Chernihiv Oblast, northern Ukraine. Liubech is located north of the capital of Ukraine, Kyiv, and located near the border with Belarus. It hosts the administration of Liubech settl ...

in the

Ukrainian SSR The Ukrainian Soviet Socialist Republic, abbreviated as the Ukrainian SSR, UkrSSR, and also known as Soviet Ukraine or just Ukraine, was one of the Republics of the Soviet Union, constituent republics of the Soviet Union from 1922 until 1991. ...

, and the other in eastern

Siberia Siberia ( ; , ) is an extensive geographical region comprising all of North Asia, from the Ural Mountains in the west to the Pacific Ocean in the east. It has formed a part of the sovereign territory of Russia and its predecessor states ...

. The ''duga'' system was extremely powerful, reaching over 10 MW, and emitted in the

shortwave radio Shortwave radio is radio transmission using radio frequencies in the shortwave bands (SW). There is no official definition of the band range, but it always includes all of the High frequency, high frequency band (HF), which extends from 3 to 30& ...

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 Amateur radio, also known as ham radio, is the use of the radio frequency radio spectrum, spectrum for purposes of non-commercial exchange of messages, wireless experimentation, self-training, private recreation, radiosport, contesting, and emer ...

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 was a source of speculation, giving rise to theories such as Soviet

brainwashing Brainwashing is the controversial idea that the human mind can be altered or controlled against a person's will by manipulative psychological techniques. Brainwashing is said to reduce its subject's ability to think critically or independently ...

and

weather modification Weather modification is the act of intentionally manipulating or altering the weather. The most common form of weather modification is cloud seeding, which increases rainfall or snowfall, usually for the purpose of increasing the local water su ...

experiments. However, because of its distinctive transmission pattern, many experts and amateur radio hobbyists realized it was an over-the-horizon radar system.

NATO The North Atlantic Treaty Organization (NATO ; , OTAN), also called the North Atlantic Alliance, is an intergovernmental organization, intergovernmental Transnationalism, transnational military alliance of 32 Member states of NATO, member s ...

military intelligence had already given it the

reporting name Reporting may refer to * any activity that leads to reports * in particular business reporting * Data reporting * Sustainability reporting * Financial reporting * international reporting of financial information for tax purposes under the OECD's ...

''STEEL WORK'' or ''STEEL YARD'', based on the massive size of the antenna, which spanned in length and in height. This massive structure formed a

phased array In antenna (radio), antenna theory, a phased array usually means an electronically scanned array, a computer-controlled Antenna array, array of antennas which creates a radio beam, beam of radio waves that can be electronically steered to point ...

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 Soviet Union was formally dissolved as a sovereign state and subject of international law on 26 December 1991 by Declaration No. 142-N of the Soviet of the Republics of the Supreme Soviet of the Soviet Union. Declaration No. 142-Н of ...

History

Genesis

The Soviets had been working on

for their

anti-ballistic missile An anti-ballistic missile (ABM) is a surface-to-air missile designed to Missile defense, destroy in-flight ballistic missiles. They achieve this explosively (chemical or nuclear), or via hit-to-kill Kinetic projectile, kinetic vehicles, which ma ...

systems through the 1960s, but most of these had been line-of-sight systems that were useful for rapid analysis and interception only. None of these systems had the capability to provide early warning of a launch, within seconds or minutes of a launch, which would give the defences time to study the attack and plan a response. At the time, the Soviet

early warning satellite An early warning satellite is an artificial satellite that detects ballistic missile launches in order to provide rapid early warning of a potential missile attack. Modern examples are often multi-purpose vehicles also supporting other wide-area ...

network was not well developed. An over-the-horizon radar sited in the USSR would help solve this problem, and work on such a system for this associated role started in the late 1960s. The first experimental system, Duga, was built outside

Mykolaiv Mykolaiv ( ), also known as Nikolaev ( ) is a List of cities in Ukraine, city and a hromada (municipality) in southern Ukraine. Mykolaiv is the Administrative centre, administrative center of Mykolaiv Raion (Raions of Ukraine, district) and Myk ...

Ukraine Ukraine is a country in Eastern Europe. It is the List of European countries by area, second-largest country in Europe after Russia, which Russia–Ukraine border, borders it to the east and northeast. Ukraine also borders Belarus to the nor ...

, successfully detecting rocket launches from

Baikonur Cosmodrome The Baikonur Cosmodrome is a spaceport operated by Russia within Kazakhstan. Located in the Kazakh city of Baikonur, it is the largest operational space launch facility in terms of area. All Russian Human spaceflight, crewed spaceflights are l ...

at . 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 Novaya Zemlya (, also , ; , ; ), also spelled , is an archipelago in northern Russia. It is situated in the Arctic Ocean, in the extreme northeast of Europe, with Cape Flissingsky, on the northern island, considered the extreme points of Europe ...

. Both of these radar systems were aimed east and were fairly low power, but with the concept proven, work began on an operational system. The new Duga-1 systems, built in 1972, used a transmitter and receiver separated by about .

"Russian Woodpecker"

At some point in 1976, a new and powerful radio signal was detected simultaneously worldwide, and quickly dubbed 'the Woodpecker' by

operators. Transmission power on some Woodpecker transmitters was estimated to be as high as 10MW equivalent isotropically radiated power. Even prior to 1976, a similar woodpecker-style interference is remembered by radio amateurs occurring in the high frequencies. As early as 1963, or before, radio amateurs were calling this "the Russian Woodpecker". Little is known about the power levels or Russian designation but it was probably a forerunner of the Duga radar systems. It was also speculated at that time, at least among radio amateurs, that this was an over-the-horizon radar. These signals even caused interference on 27MHz 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.

Triangulation In trigonometry and geometry, triangulation is the process of determining the location of a point by forming triangles to the point from known points. Applications In surveying Specifically in surveying, triangulation involves only angle m ...

by amateur radio hobbyists and

showed the signals came from a location in present-day

, at the time called the

Ukrainian Soviet Socialist Republic The Ukrainian Soviet Socialist Republic, abbreviated as the Ukrainian SSR, UkrSSR, and also known as Soviet Ukraine or just Ukraine, was one of the Republics of the Soviet Union, constituent republics of the Soviet Union from 1922 until 1991. ...

(part of the

USSR The Union of Soviet Socialist Republics. (USSR), commonly known as the Soviet Union, was a List of former transcontinental countries#Since 1700, transcontinental country that spanned much of Eurasia from 1922 until Dissolution of the Soviet ...

). Confusion due to small differences in the reports being made from various sources led to the site being variously located near

Kyiv Kyiv, also Kiev, is the capital and most populous List of cities in Ukraine, city of Ukraine. Located in the north-central part of the country, it straddles both sides of the Dnieper, Dnieper River. As of 1 January 2022, its population was 2, ...

Minsk Minsk (, ; , ) is the capital and largest city of Belarus, located on the Svislach (Berezina), Svislach and the now subterranean Nyamiha, Niamiha rivers. As the capital, Minsk has a special administrative status in Belarus and is the administra ...

Gomel Gomel (, ) or Homyel (, ) is a city in south-eastern Belarus. It serves as the administrative centre of Gomel Region and Gomel District, though it is administratively separated from the district. As of 2025, it is the List of cities and largest ...

Chernihiv Chernihiv (, ; , ) is a city and municipality in northern Ukraine, which serves as the administrative center of Chernihiv Oblast and Chernihiv Raion within the oblast. Chernihiv's population is The city was designated as a Hero City of Ukraine ...

. All of these reports were describing the same deployment, with the transmitter only a few kilometers southwest of Chernobyl (south of Minsk, northwest of Kyiv) and the receiver about northeast of Chernobyl (just west of Chernihiv, south of Gomel). At one time there was speculation that several transmitters were in use. The radar system was given the code 5Н32-West by the Soviets, and was set up in two closed towns. Liubech-1 held the two transmitters and Chernobyl-2 the receivers. Unknown to civilian observers at the time, NATO was aware of the new installation. A second installation was built near

Komsomolsk-on-Amur Komsomolsk-on-Amur ( rus, Комсомольск-на-Амуре, r=Komsomolsk-na-Amure, p=kəmsɐˈmolʲsk nɐ‿ɐˈmurʲə) is a types of inhabited localities in Russia, city in Khabarovsk Krai, Russia, located on the west bank of the Amur R ...

, in Bolshya Kartel and Lian, but did not become active for some time.

NATO reporting name

The NATO reporting name for the Duga-1 is often quoted as STEEL YARD. Many online and several print references use this name. However some sources also use the term STEEL WORK (or STEEL WORKS). As any "official" sources using NATO Reporting Names are likely to be classified, establishing the true name will be difficult. The earliest found open source mention of a NATO Reporting Name for this system, a reference publication in print while the system was still active, unambiguously uses the term STEEL WORK. Jane's Information Group is an often quoted open source reference for information across several military fields and subjects. Their "Jane's Radar and Electronic Warfare Systems", several editions over a number of years, uses the term "Steel Works".

Civilian identification

Even from the earliest reports it was suspected that the signals were tests of an

, and this remained the most popular hypothesis during the

Cold War The Cold War was a period of global Geopolitics, geopolitical rivalry between the United States (US) and the Soviet Union (USSR) and their respective allies, the capitalist Western Bloc and communist Eastern Bloc, which lasted from 1947 unt ...

. Several other theories were floated as well, including everything from jamming western broadcasts to submarine communications. The broadcast jamming theory was discarded early on when a monitoring survey showed that

Radio Moscow Radio Moscow (), also known as Radio Moscow World Service, was the official international broadcasting station of the Union of Soviet Socialist Republics until 1993, when it was reorganized into Voice of Russia, which was subsequently reorga ...

and other pro-Soviet stations were just as badly affected by woodpecker interference as Western stations. As more information about the signal became available, its purpose as a radar signal became increasingly obvious. In particular, its signal contained a clearly recognizable structure in each BPSK modulated

pulse In medicine, the pulse refers to the rhythmic pulsations (expansion and contraction) of an artery in response to the cardiac cycle (heartbeat). The pulse may be felt ( palpated) in any place that allows an artery to be compressed near the surfac ...

, which was eventually identified as a 31-bit

pseudo-random A pseudorandom sequence of numbers is one that appears to be statistically random, despite having been produced by a completely deterministic and repeatable process. Pseudorandom number generators are often used in computer programming, as tradi ...

binary sequence with properties much like

Barker code In telecommunication technology, a Barker code or Barker sequence is a finite sequence of digital values with the ideal autocorrelation property. It is used as a synchronising pattern between the sender and receiver of a stream of bits. Explanat ...

s, with a bit-width of 100

μs A microsecond is a unit of time in the International System of Units (SI) equal to one millionth (0.000001 or 10−6 or ) of a second. Its symbol is μs, sometimes simplified to us when Unicode is not available. A microsecond is to one second, ...

resulting in a 3.1 ms pulse. The auto-correlation of this pulse/sequence results in a single 100μs pulse 31 times the amplitude of the received sequence, giving a resolution of (the distance light travels in 50μs) and process gain of almost 30 dB. This system took advantage of

pulse compression Pulse compression is a signal processing technique commonly used by radar, sonar and Ultrasound, echography to either increase the range angular resolution, resolution when pulse length is constrained or increase the Signal-to-noise ratio, signal ...

to increase the power of the received echoes thereby increasing the sensitivity and effective range. 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. These further installations allowed for more precise pin-pointing of potential targets or missiles in multiple dimensions thanks in part to the properties of the

s that allow for multiple radars operating on the same frequencies without significant interference. In 1988, the U.S.

Federal Communications Commission The Federal Communications Commission (FCC) is an independent agency of the United States government that regulates communications by radio, television, wire, internet, wi-fi, satellite, and cable across the United States. The FCC maintains j ...

(FCC) conducted a study on the Woodpecker signal. Data analysis showed a pulse repetition interval (PRI) of about 90ms, a frequency range of 7 to 19MHz, a bandwidth of 0.02 to 0.8MHz, and typical transmission time of 7 minutes. The pulses transmitted by the Woodpecker had a wide bandwidth, typically 40 kHz. Their repetition frequencies were 10Hz, 16Hz and 20Hz with the most common frequency of 10Hz, while the 16Hz and 20Hz modes were rarely used.

Jamming the Woodpecker

To combat this interference, amateur radio operators attempted to jam the signal by transmitting synchronized unmodulated continuous wave signals at the same pulse rate as the offending signal. They formed a club called The Russian Woodpecker Hunting Club.

Signal disappearance

Starting in the late 1980s, even as the FCC was publishing studies, the signals became less frequent, and in 1989, they disappeared. 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

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. The satellite system provides immediate, direct and highly secure warnings, whereas any radar-based system is subject to jamming, and the effectiveness of OTH systems is also subject to atmospheric conditions. According to some reports, the

installation in the

Russian Far East The Russian Far East ( rus, Дальний Восток России, p=ˈdalʲnʲɪj vɐˈstok rɐˈsʲiɪ) is a region in North Asia. It is the easternmost part of Russia and the Asia, Asian continent, and is coextensive with the Far Easte ...

was taken off combat alert duty in November 1989, and some of its equipment was subsequently scrapped. The original Duga-1 site lies within the

Zone of Alienation The Chernobyl Nuclear Power Plant Zone of Alienation, also called the 30-Kilometre Zone or simply The Zone, was established shortly after the 1986 Chernobyl disaster in the Ukrainian SSR of the Soviet Union. Initially, Soviet authorities declar ...

around the Chernobyl power plant. As of today , 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 Mukachevo (, ; , ; see name section) is a city in Zakarpattia Oblast, western Ukraine. It is situated in the valley of the Latorica River and serves as the administrative center of Mukachevo Raion. The city is a rail terminus and highway junct ...

and

Sevastopol Sevastopol ( ), sometimes written Sebastopol, is the largest city in Crimea and a major port on the Black Sea. Due to its strategic location and the navigability of the city's harbours, Sevastopol has been an important port and naval base th ...

, most of the antenna still stands and is often used by radio amateurs who visit the area using their own portable radio equipment.

Locations

The original Duga was the first experimental system. It was built outside the Black Sea port of

in southern

, and successfully detected rocket launches from

about away. Duga is able to track launches from the Far East and from submarines in the

Pacific Ocean The Pacific Ocean is the largest and deepest of Earth's five Borders of the oceans, oceanic divisions. It extends from the Arctic Ocean in the north to the Southern Ocean, or, depending on the definition, to Antarctica in the south, and is ...

, as the missiles fly towards

in the Arctic Ocean. This huge radar complex was restored in 2002 after a fire seriously damaged it. The transmitter was located at and the receiver at . It appears that the original Duga transmit and receive sites near Mykolaiv, Ukraine were demolished in 2006. The original Duga was supplanted by a pair of installations: western, Duga-1, and eastern, Duga-2. Duga-1 was built in northern Ukraine, between

and

-2. The receiver is located at , 12 kilometers west-north-west of Chernobyl; the transmitter is located at about northeast of Chernobyl (just west of

, south of

). Duga-2, the eastern system, is located near

Khabarovsk Krai Khabarovsk Krai (, ) is a federal subjects of Russia, federal subject (a krai) of Russia. It is located in the Russian Far East and is administratively part of the Far Eastern Federal District. The administrative centre of the krai is the types of ...

, with the receiver at , some southeast of the city, and the transmitter at , north of the city.

Media appearances

The Ukrainian-developed computer game series ''

S.T.A.L.K.E.R. ''S.T.A.L.K.E.R.'' is a first-person shooter survival horror video game franchise developed by Ukrainian game developer GSC Game World. The series is set in an Parallel universe (fiction), alternate version of the present-day Chernobyl Exclusio ...

'' has a plot focused on the Chernobyl Nuclear Power Plant and the

nuclear accident A nuclear and radiation accident is defined by the International Atomic Energy Agency (IAEA) as "an event that has led to significant consequences to people, the environment or the facility." Examples include radiation poisoning, lethal effect ...

there. The game features many actual locations in the area, including the Duga-1 array. The array itself appears in '' S.T.A.L.K.E.R.: Clear Sky'' in the fictional city of Limansk-13. While the 'Brain Scorcher' from '' S.T.A.L.K.E.R.: Shadow of Chernobyl'' was inspired by theories that Duga-1 was used for mind control, it does not take the form of the real array. However, in the 2024 entry of the series '' S.T.A.L.K.E.R. 2: Heart of Chornobyl'', the site of the Duga-1 array is an explorable part of the map. In the story, the game's "Monolith" faction attempts to use Duga-1 similarly to how the "Brain Scorcher" is used in '' S.T.A.L.K.E.R.: Shadow of Chernobyl''.

Markiyan Kamysh Markiyan Kamysh (, born 19 October 1988) is a Ukrainian novelist, best known for his works about the Chernobyl nuclear power plant and its environs. Biography Kamysh's father was a Chernobyl liquidator. From 2005-2009, Kamysh studied history ...

'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. TOP10 books of 2019 according to ''

La Repubblica (; English: "the Republic") is an Italian daily general-interest newspaper with an average circulation of 151,309 copies in May 2023. It was founded in 1976 in Rome by Gruppo Editoriale L'Espresso (now known as GEDI Gruppo Editoriale) and l ...

'' as one of the ''"Constellations of the ten books that best reflect the spirit of the times".''

The Guardian ''The Guardian'' is a British daily newspaper. It was founded in Manchester in 1821 as ''The Manchester Guardian'' and changed its name in 1959, followed by a move to London. Along with its sister paper, ''The Guardian Weekly'', ''The Guardi ...

called it a ''“remarkable book”.'' In '' Call of Duty: Black Ops'', the map "Grid" is placed in Pripyat near the Duga-1 array. A game later in the series, ''

'', uses the Duga as location for a possible final mission and as a map in the Zombies game-mode “Outbreak”, the map being appropriately named "Duga". The said map has rappel lines that can take the player(s) up to the top or middle of the Duga, despite the actual radar array lacking this. The Duga antenna array is also featured on the revised map "Verdansk '84" in the game Call of Duty: Warzone. The 'Russian woodpecker' appears in Justin Scott's novel ''The Shipkiller''. The Duga at Chernobyl was the focus of the 2015 documentary film, '' The Russian Woodpecker'', by Chad Gracia. 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. The documentary, which won numerous awards, also includes drone video footage of the array and handheld video footage of the surroundings as well as a climb to the top by the cinematographer, Artem Ryzhykov. The film also proposes a

conspiracy theory A conspiracy theory is an explanation for an event or situation that asserts the existence of a conspiracy (generally by powerful sinister groups, often political in motivation), when other explanations are more probable.Additional sources: * ...

that the

Chernobyl disaster On 26 April 1986, the no. 4 reactor of the Chernobyl Nuclear Power Plant, located near Pripyat, Ukrainian Soviet Socialist Republic, Ukrainian SSR, Soviet Union (now Ukraine), exploded. With dozens of direct casualties, it is one of only ...

was engineered to cover up failures in the radar's design. The Duga radar is featured in the

drone racing Drone racing is a motorsport where participants operate radio-controlled aircraft (typically small quadcopter unmanned aerial vehicle, drones) equipped with onboard digital camera, digital video cameras, with the operator looking at a compa ...

simulator Liftoff, as "The Russian Woodpecker". 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. In wide shots, its structure was used to create

computer-generated imagery Computer-generated imagery (CGI) is a specific-technology or application of computer graphics for creating or improving images in Digital art, art, Publishing, printed media, Training simulation, simulators, videos and video games. These images ...

of the superstructure and several close-up scenes were shot directly at its location. 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. The Duga radar is heavily featured in the virtual reality game ''Proze: Enlightenment'', a suspense/puzzle game with the theory that the radar is being used by mind controlling experiments during the 1950-60s. The game actually starts with the player ascending one of the pylons on a maintenance lift. A Duga radar is featured in the 2021 video game ''Chernobylite.'' In episode 12 of the first season of the NBC science fiction series ''Debris'', the Duga radar array makes an appearance as a fictional array in the state of Virginia. The Chernobyl Duga site is featured in the

Science Channel Science Channel (often simply branded as Science; abbreviated to SCI) is an American pay television channel owned by Warner Bros. Discovery. The channel features programming focusing on science related to wilderness survival, engineering, manu ...

series "Mysteries of the Abandoned" (season 1, episode 1)."Nazi Ghost Town", discovery.com
/ref>

References

External links

Chernobyl-2. Secret Military Facility in the territory of exclusion zone. Text and photos
2008
OTH-Radar "Chornobyl - 2" and Center of space-communication

"Circle" is an auxiliary system for OTH-Radar "Chornobyl - 2"

''Miami Herald'', July 1982.

globalsecurity.org
Some pictures of Chernobyl-2

'Duga' photos at englishrussia.com

Chernobyl-2

The Top Secret Military Base Hidden in Chernobyl’s Irradiated Forest

Obsidian Urbex Photography , Photos taken in 2016
{{Soviet Radar Cold War broadcasting Cold War history of the Soviet Union Amateur radio history International broadcasting Soviet military radars 1976 establishments in the Soviet Union 1989 disestablishments in the Soviet Union Science and technology in the Soviet Union Over-the-horizon radars Military equipment introduced in the 1970s Military installations established in 1976 Military installations closed in 1989