The Russian Woodpecker: Official Chilly Struggle hen nests in big antenna
On July 4, 1976, as Americans celebrated the country’s bicentenary with beer and bottle rockets, a strong signal began to disrupt shortwave, marine, aerospace, and telecommunications signals around the world. The signal was a fast 10 Hz knock that sounded like a woodpecker or a helicopter hopping on the roof. It had a wide bandwidth of 40 kHz and sometimes exceeded 10 MW.
This was during the Cold War, and many people concluded that it was some sort of Soviet mind control scheme or weather control experiment. However, amateur radio operators traced the mysterious signal to a radar antenna over the horizon near Chernobyl in Ukraine (then part of the USSR) and named it the Russian Woodpecker. Here is a clip of the sound.
The frequency hopping woodpecker signal was so strong that it made communication on certain channels impossible and, under the right conditions, could even be heard over telephone lines. Several countries filed official complaints with the USSR through the United Nations, but the Russian woodpecker was unstoppable. Russia would not even accept the existence of the signal, which has since been due to an immense antenna structure nearly half a mile long and 490 feet high, and slightly higher than the Great Pyramid in Giza.
This imposing steel structure is located in the irradiated forest near Pripyat, an idyllic town that was founded in 1970 to house the workers of the Chernobyl nuclear power plant. Pictured above is the transmitter, also known as Duga-1, Chernobyl-2, or Duga-3, depending on who you ask. The area is 30 miles northeast of Chernobyl and is simply referred to as the Boy Scout Camp on old Soviet maps. Today everything is in the Chernobyl exclusion zone.
It was such a secret that the government denied its existence and yet was heard all over the world. What was this mammoth installation used for?
Distant early warning
The Duga radar was one of two transmitter / receiver pairs built in response to the DEW Line, a collection of antennas built over the Arctic Circle in collaboration between the United States and Canada. As with any over-the-horizon radar, the theory behind the Russian system was that Moscow would have about 25 minutes to respond to ICBMs in kind rather than only about 10 minutes to duck, cover and say goodbye to the world. To get a better idea of the size of this thing, check out Tom Scott’s short tour in the video embedded below.
The DEW, Mid-Canada and Pinetree radar lines. Image via Wikipedia
Over-the-horizon radar is based on a similar phenomenon that offers such a long range for amateur radio – the signals bounce off the ionosphere and can thus overcome the curvature of the earth, which means that launches can be detected much earlier than with standard ground penetrating radar.
In the documentary The Russian Woodpecker 2015, a film team led by an artist from Kiev tries to uncover the secrets of the antenna. He believes the Chernobyl nuclear incident was staged to divert attention from the structure slated for an upcoming inspection that would never happen.
According to the documentary, the Duga antenna cost twice as much as the Chernobyl plant itself – around 7 billion rubles. It is difficult to put these costs in historical context. Using Treasury Reporting’s exchange rates as of June 30, 1976, we find that the exchange rate at that time was 0.7550 rubles to dollars. That puts the 1976 cost of around $ 9.27 billion. Adjusted for inflation, that’s $ 43.16 billion in 2021 – a staggering sum that makes us question the cost assessment of the documentary (and the accuracy of our own conversion process).
Some sources say the radar system never worked. Other sources claim this was the case and that they were able to detect every single shuttle launch with it. And when it was reported that the woodpecker was interfering with Russian SOS signals, they changed the frequency. But after they did that, it stopped working because Aurora borealis intervened.
Production of Moscow silencers
Eventually, businesses and individuals built blanker circuits to stop the incessant knocking. Conventional interference blanking circuits look for a short pulse duration with a fast rise time and generate a signal to turn off a gate in the signal path. However, these would be useless to drown out the woodpecker as they do not work with pulses of lower amplitude.
The Moscow silencer WB-1. Image via QRZ forums
The problem with fading out the woodpecker signal was that it had a wide bandwidth and inconsistent pulses. Ionospheric reflection stretched the pulses and sometimes created echoes, making them a slap in the mouth. To make matters worse, they often looked like normal signals, which made it even more difficult to isolate the woodpecker from the desired signal.
The Datong SRB2 Woodpecker Blanker. Image about radio world
A popular device was the AEA Moscow Muffler (PDF), in which an internal signal of 10 or 16 Hz was generated to block out the woodpecker. However, when the ionosphere stretched the pulses, the pulse width of the blanker had to be increased to compensate for this, which often meant that the desired signal was lost in the shuffle.
Another device, the Datong SRB2, was much more of a set-it-and-forget-it deal (PDF, page 39). The SRB2 worked similarly to the Moscow silencer in that it generated an internal clock and compared it with the woodpecker signal.
The nice thing about the SRB2 is that it was automatic. Once a match was found, it adjusted the blocking pulse by dialing in the pulse width, the number of blanking pulses and their ideal positions. Conversely, the Moscow silencer used fixed-width pulses, so you had to keep playing with them to block out the signal.
The interference of the Russian woodpecker stopped after the fall of the Soviet Union in 1989. At this point, their existence was finally confirmed by the Soviet government. By then, the Russians had switched to satellites for their early warning purposes.
In 2013, a similar signal began to terrorize the shortwave, albeit not as strong as the original. It is believed to have originated from a new Russian OTH radar system called Container, which appears to be almost the size of Duga. If you’d like to try it out, tune in to shortwave 14.270 and let us know what you hear!
[Main image source: The Duga radar antenna, human for scale. Image by Corsairoz CC BY-SA 4.0]