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Rewind - The Russian Woodpecker
The Russian Woodpecker was a notorious Soviet signal that was heard on the shortwave radio bands
worldwide between July 1976 and December 1989. It sounded like a sharp, repetitive tapping noise, at
10 Hz, giving rise to the "Woodpecker" name. The random frequency hops disrupted legitimate broadcast,
amateur radio, and utility transmissions and resulted in thousands of complaints by many countries
worldwide. The signal was long believed to be that of an over-the-horizon radar (OTH) system. This
theory was publicly confirmed after the fall of the Soviet Union, and is now known to be the Duga-3
system, part of the Soviet ABM early-warning network.
The Appearance Of The Woodpecker
Starting in 1976 a new and powerful radio signal was detected worldwide, and quickly dubbed the
Woodpecker by radio amateurs. Transmission power on some woodpecker transmitters was estimated to
be as high as 10 MW EIRP. As well as disrupting shortwave amateur radio and broadcasting it could
sometimes be heard over telephone circuits due to the strength of the signals. This led to a thriving
industry of "Woodpecker filters" and noise blankers. One idea radio amateurs had to combat this
interference was to attempt to "jam" the signal by transmitting synchronized unmodulated continuous
wave signals, at the same pulse rate as the offending signal. This idea was considered, but abandoned as
impractical. Simple CW pulses didn't appear to have any effect. However, playing back recordings of the woodpecker transmissions sometimes caused the woodpecker transmissions to shift frequency leading to speculation that the receiving stations were able to differentiate between the "signature" waveform of the woodpecker transmissions and a simple pulsed carrier.
Identification Of The Woodpecker
Triangulation quickly revealed the signals to come from Ukraine. Confusion due to small differences in the
reports being made from various military sources led to the site being alternatively located near Kiev,
Minsk, Chernobyl, Gomel or Chernihiv. All of these reports were describing the same deployment, with the transmitter only a few kilometers southwest of Chernobyl (south of Minsk, northwest of Kiev) and the
receiver about 50 km northwest of Chernobyl (just west of Chernihiv, south of Gomel). Unknown to most
observers, NATO was well aware of the new radar installation, which they referred to as Steel Yard. Even
from the earliest reports, it was suspected they were tests of an over-the-horizon radar and this remained
the most popular theory during the cold war. Several other theories were floated as well, including
everything from jamming western broadcasts to submarine communications. The broadcast jamming
theory was debunked early on when a monitoring survey showed that Radio Moscow and other pro-Soviet
stations were just as badly affected by woodpecker interference as Western stations. More speculative
explanations were also offered, claiming it was a system for weather control or even an attempt at mass subconscious mind control. 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 pulse, which was eventually identified as a 31-bit pseudo-random binary sequence, with a bit-width of
100 μs resulting in a 3.1 ms pulse. This sequence is usable for a 100 μs chirped pulse
amplification system, giving a resolution of 15 km (10 mi) (the distance light travels in 50 μs). 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, this conclusion became inescapable. In 1988, the
Federal Communications Commission conducted a study on the Woodpecker signal. Data analysis showed
an inter-pulse period of about 90 ms, a frequency range of 7 to 19 MHz, a bandwidth of 0.02to 0.8 MHz,
and typical transmission time of 7 minutes.
Disappearance Of The Woodpecker
Starting in the late 1980s, even as the FCC was publishing studies of the signal, the signals became less
frequent, and in 1989 disappeared altogether. Today Google Map photography of the area shows that
the antenna has been removed. The original Duga-3 site lies within the 30 kilometer Zone of Alienation
around the Chernobyl power plant. It appears to have been permanently deactivated, since their
continued maintenance did not figure in the negotiations between Russia and Ukraine over the active
early warning radars at Mukachevo and Sevastopol. The antenna still stands, however, and has been
reported to have been used by amateurs as a transmission tower (using their own antennas) and has
been extensively photographed. Text from http://en.wikipedia.org/wiki/Russian_Woodpecker
Further pictures and information available from
http://www.artificialowl.net/2008/12/abandoned-giant-duga-3-system-antenna.html [wia]
| February, 2009 | |
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