The mystery of the Russian woodpecker

What is the mystery behind the Russian woodpecker and how does it relate to the communication stuff.?

People used to walk across the endless cold wilderness in Ukraine and meet some enormous metal structures located in the snow near the famous Chernobyl site at Pripyat (the famous site relates the Chernobyl reactor accident). In first glimpse it looks like someone stuck a huge metal wall in the middle of the wilderness. The conformation was built of a large number of metal arrays. These arrays were enormous and it's measured 210 meters wide by 85 meters tall what made people try guess the true purpose of these huge metal bars. The huge constellation was first identified in the 70'S and 80'S during the dying days of the Cold War.?

This construction was a set of massive arrays of antennae constructed in secret in woods close to Chernobyl. Two massive arrays were built near Chernobyl with a third located on the Russian Pacific Coast near Sakhalinsk. The arrays were built by the Soviet Union to provide an early warning radar system. The purpose of these arrays was to allow the Soviets to detect any incoming ballistic missiles from America and European NATO members. The " Woodpecker" system is an over the horizon radar that enables to overcome the curve of the earth.?Any shortwave radio owner was familiar with a sharp, repetitive "rat tat tat tat" noise. This interference permeated the airwaves and disrupted over air communications and television signals all over the world. This characteristic tapping sound gave the device(s) its now-famous nickname "The Russian Woodpecker" or the Duga Radar system.

The?" Russian woodpecker " consisted of over three hundred individual transmitter elements. Each array operated at very high power levels, in some cases as much as 10 million watts. The Soviets had little regard for which frequency they would use and a 10MW transmission become such a nuisance that receivers began to include "Woodpecker Blankers" in their circuitry to attempt to filter out the interference.

Normally radar systems have a problem that relates the bend of the Earth surface. The maximum range of these radars is limited by the radio horizon – slightly far away than the optical horizon. OTH radars use very long wave lengths with special properties of propagation.?

There are several ways to implement over the horizon radars, some of them relates very long wave length like OTH-SW.?OTH-SW radars use a very low transmission frequency from 3 MHz up to 20 MHz. These electromagnetic waves tend to bend or “diffract” around edges or curves, they are coupled to the conductive ocean surface forming a “ground wave”. They can bend over the horizon and will follow the curvature of the earth.

It is also possible to build radar that has “over the horizon” range, obtained by “bouncing” or “backscattering” radio waves off the ionosphere, the ionized layer at the top of the atmosphere.?The advantage of the low frequency usage is that radio waves of these frequencies are refracted (bent) by the ionosphere so that the waves return to the Earth’s surface at long distances beyond the horizon, as shown in the figure. This permits target detection at very long distances (500 to 2,000 nautical miles). Thus, an over-the-horizon (OTH) radar can detect aircraft at distances up to 10 times that of a ground-based microwave air-surveillance radar, whose range is limited by the curvature of the Earth. Besides detection and tracking of aircraft at long ranges, an OTH radar can be designed to detect ballistic missiles.

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