In the 1970s and 1980s, if you were to tune in to shortwave radio frequencies across the world, you would hear a ”rat tat tat tat” noise permeating from seemingly nowhere. This ticking sound sank infused into communications networks around the world and even disrupted television signals.
It was soon found that the signal was coming from a massive device built by the Russians, nicknamed the “Woodpecker,” a reference to its repetitive tapping noise.
The woodpecker was a network of antennas with 2 arrays hidden deep in the woods near Chernobyl, Ukraine and a third one on the Russian Pacific coast. This mysterious and obtrusive antenna network together formed an early warning radar system called Duga that the Soviets implemented to detect incoming ballistic missiles.
Image Source: Wikimedia
It’s hard to grasp the scale of this massive antenna arrays without reference. One near Chernobyl, the Duga-3 Array, was 2010 meters wide, 85 meters tall, and made up of more than 300 individual transmitters. That’s the equivalent width of 4.5 Empire State Buildings laid end to end and the height of a 28-story building. The devices operated at extremely high power levels, requiring 10 million watts, needed to achieve proper resolution. These power levels allowed the signals to reach massive distances without any form of amplification – thus making it good for missile detection.
The signal the antennas output would bounce around frequencies in the range of 7 to 20 MHz and a bandwidth of 40 kHz. As the entire system was first shrouded in mystery to the rest of the world, the signal source was quickly triangulated by both Hobbyists and NATO to be originating from modern-day Ukraine.
HAM radio operators built woodpecker silencing devices that would send out a wave essentially reverse to the signal transmitted from the Duga arrays. These two opposite waves would cancel each other out, the same way that active noise canceling works today, thus removing the annoying “rat tat tat tat” noise from radio waves.
While the large antennas and the signals that exuded from them pestered the world’s radio signals, they served a rather innovative purpose at the time.
Image Source: Concerning Reality
The system worked by detecting small variances in the return signal from the radio waves it transmitted. The ground would naturally return a signal bounced back from the transmitted waves, but they would be essentially the same as those transmitted. Instead of listening for this return, receiving arrays would listen for the transmitted signal at a slightly higher pitch. Thanks to something called the Doppler effect, a missile flying through the air would return a higher pitched signal. Much like how a police siren sounds higher when it’s coming towards you, the return signal bounced of a missile would have a higher frequency. By tracking this change, the Soviets could detect and track missiles at great distances.
Luckily, a higher pitch return was never detected, because if it was, a nuclear war likely would’ve broken out.
When the Cold War came to an end in 1989 and the Soviet Union broke apart, the woodpecker eventually fell silent and ultimately obsolete due to new satellite systems.
So, that’s the story of a mysterious tapping noise that permeated the world’s radio signals for nearly two decades and a missile detection network that could’ve triggered WWIII.