Tuesday 20 March 2018

The Russian Woodpecker

Anyone who listened to shortwave radio or was a ham radio operator from the mid 1970s to the late 1980s will be familiar with a sharp, repetitive “rat tat tat tat” noise that permeated the airwaves disrupting communications and television signals the world over. Nicknamed the “Woodpecker”, the signal came from a massive array of antennas hidden deep in the woods—two located near Chernobyl in Ukraine, and a third one on the Russian Pacific coast, near the island of Sakhalnsk. These antennas formed part of an early warning radar system called Duga, that the Soviets developed to detect incoming ballistic missiles from America.
Photo credit: Bert Kaufmann/Flickr
The transmitting antennas used by Duga were massive. The one near Chernobyl was 210 meters wide and 85 meters tall and was made of more than three hundred individual transmitting elements. They operated at extremely high power levels, as high as 10 million watts, that completely drowned any legitimate transmissions taking place at that frequency. Apart from disrupting shortwave amateur radio and broadcasting, including Moscow’s own radio stations, the repetitive tapping noise could sometimes be heard over telephone circuits as well due to the strength of the signals.
The Soviets used whatever frequency was suitable at that particular time, operating often in the 3 MHz to 30 MHz range, without any regard for frequency allocation and planning. The signal became such a nuisance that some receivers such as amateur radios and televisions actually began including 'Woodpecker Blankers' in their circuit designs in an effort to filter out the interference.
Although the Soviets never acknowledged the Woodpecker, it became apparent where the signals were coming from and that there were more than one source. NATO was confident that it was an over-the-horizon radar, but they were not sure what the radar was used to scan for. Others thought its purpose was to jam western broadcasts or disrupt submarine communications. The secrecy led some to believe that it was a system for weather control or even an attempt at mind control.
Photo credit: Matt White/Flickr
As more information about the signal became available, its purpose as a radar signal became increasingly obvious. Analysis of the signal revealed that it contained a sequence of pulses identified to be a 31-bit pseudo-random binary sequence that’s usable on a chirped pulse amplification system, giving the radar a resolution of not a very precise 15 km. When a second Woodpecker appeared, this one located in eastern Russia but also pointed toward the US and covering blank spots in the first system's pattern, the radar’s real purpose became as clear as day.
In Russian Strategic Nuclear Forces, published in 2001, author Bukharin disclosed that the first experimental system, built outside Mykolaiv in Ukraine, successfully detected rocket launches from Baikonur Cosmodrome located 2,500 kilometers away. A second prototype, built on the same site, was able to track launches from the far east and submarines in the Pacific Ocean as the missiles flew towards Novaya Zemlya despite it being fairly low power. Only when the concept was proven, work began on the ultra-high powered operational system.
The Woodpecker eventually fell silent in 1989 as the Cold War came to an end and the Soviet Union broke apart. In any case, the system had become technologically obsolete having been replaced by satellite based early-warning systems that were more accurate, more secure and less prone to atmospheric interferences.
The Ukrainian government now allow tourists to visit the still standing antennas of Duga. Because it is located within the Chernobyl Exclusion Zone—a 30-km exclusion zone created around the site of the Chernobyl nuclear reactor disaster—permits must be obtained in advance.
Photo credit: Ernestas Narmontas/Flickr
Photo credit: Daniel Weber/Flickr
Photo credit: Kevin Dooley/Flickr
Photo credit: Jorge Franganillo/Flickr
Photo credit: Matt White/Flickr
Photo credit: Bert Kaufmann/Flickr
Inside the Duga training center. Photo credit: thepurpleblob/Flickr

The Duga control center.

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