Tuesday, October 19, 2010

Mysterious Cold War Signals

An important part of the Cold War was fought in the aether. All sorts of radio signals, communications in voice, Morse or in data, radar and navigation signals were transmitted and intercepted by East and West. A shortwave receiver with a good antenna was, and still is, all you need to discover innumerable signals. Of course, these signals also caught the attention of both Intelligence organisations and civilian radio amateurs.

TechELINT (Technical Electronic Intelligence), the interception and analysis of signals from weapons systems, navigation and radar systems, were an important part of the Cold War, and still are an indispensable part of modern intelligence gathering and warfare. What system is a signal originating from, what does it tell about the opponent's equipment and its performance, and how can we take countermeasures? Advances in electronics for communications and weapons systems constantly fueled a race between those who developed various types of transmitters and those who wanted to intercept and analyse these signals.

Often, the secrets behind the signals were revealed, either by TechELINT or espionage. However, some signals remained unidentified and some of them even rose to the stardom of mysterious Cold War signals. There was much speculation about the purpose of these signals, some of which broadcast continuously for decades. Possible explanations were occupying certain frequencies to have them available in case of a crisis or war, beacons, or even the notorious so-called Dead Hand, an autonomous launch system for nuclear missiles that supposedly would be activated if the mysterious signals were interrupted because of the elimination of Soviet military command. Scary scenarios! Nothing more than speculations.

One of these mysterious signals was nicknamed the Russian Woodpecker, because of its characteristic repetitive tapping noise. The Woodpecker's annoying high-power signal (an estimated 10 Megawatt) switched between different shortwave frequencies and disrupted legitimate utility and amateur broadcasts all over the world. The broadcast started in 1976 and continued for 10 years. For decades, its purpose remained unknown to the general public.

After the fall of the Soviet Union 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). The transmitter site was called Chernobyl-2. The system was codenamed Steel Yard by Western military intelligence, who apparently managed to photograph the transmitter site during the Cold War (image: view from on top of the gigantic Duga-3 antenna).

Normal radar works line-of-sight, the curvature of the Earth therefore limiting its range to a few hundred kilometers. This was insufficient to provide early warning in case of an attack against the Soviet Union with ICBM's (Intercontinental Ballistic Missiles). OTH radars transmit very powerful signals towards the ionosphere. The ionosphere reflects these signals over very long distances towards the ground. A very small portion is reflected back to the atmosphere and received by the OTH station. Moving objects like ICBM's create a small frequency shift (Doppler effect) in the reflected signals. It requires complex filtering to extract the very weak shifted signals from the backscatter, and its accuracy and resolution are low, but the system works perfectly for a raw early warning.

Noteworthy is that the Duga-3 site is located only 6 miles (10 Km) from the Chernobyl nuclear power plant. According to Vladimir Musiyets, former Commander of the Chernobyl-2, the installation was damaged during the 1986 Chernobyl disaster and never became operational again. The site now lays within the 18 miles (30 Km) Chernobyl exclusion zone. Some sources state that the Woodpecker continued broadcasting until 1989. These possibly refer to two other OTH sites.

Another famous mysterious Soviet signal is known under its call-sign UVB-76. The station, nicknamed The Buzzer, started in 1982 with a two-seconds beep tone and switched after a decade of operation to a monotonous 25 buzz tones per minute, every single day, until 2010. The station was extensively observed by radio amateurs (without doubt an equally monotonous job) and only a handful of voice conversations were recorded in its 28 years of operation. Its call-sign UVB-76 was revealed during one of its rare voice conversations. The purpose of The Buzzer remains unknown until today. UVB-76 stopped broadcasting in August 2010 and remains silent since then. The transmitter site is located near Povarovo, 25 miles (40 Km) north-west of Moscow, and now appears abandoned.

Another true Cold War icon are the notorious Numbers stations. The stations broadcast streams of numbers or letters in voice or Morse and are used by intelligence agencies to communicate with their agents, operating abroad. Although the Cold War officially ended, there are still many active numbers stations and new keep popping up! I previously wrote several posts on these spy stations. This weblog query will show them all.

More information on the Soviet Duga-3 OTH system is found on Global Security and Wikipedia. Photo's of the so-called Chernobyl-2 site with its huge antenna's (inside the nuclear exclusion zone) are now available on English Russia (see 14th photo with people below, to get an idea of the immense size of the antenna: each dipole cone is larger in diameter than a person!), Lost Places (hit "next" at the end of the pages) and Egorka's gallery. There's a nice video on YouTube of two guys climbing the OTH antenna (see below). If you enter 51°18′19.06″N 30°03′57.35″E in the Google Earth Fly To box, and use the 3D Buildings option, you get a good view of the enormous OTH antenna.

More on the UVB-76 Buzzer at Wikipedia. Photo's of the - abandoned - alleged UVB-76 Buzzer site are published on English Russia. More about ELINT on this previous blog post and details on the real Soviet Dead Hand missile launch system on this previous blog.

To end with a more "cheerful" note, here are some other video's of the quiet surroundings of the Woodpecker: Chernobyl's reactor No 4 with another kind of signal: radiation meter alarm. Talking about scary signals!

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