Woodpecker signal (Spectral Investigation Collective – Bureau d’études, 2006)

What is Woodpecker ? The term Woodpecker refers to the high-power OTH  radar which operated in Europe during the years 1976  – 1986. The signal from the Chernobyl-2 OTH station  (C-2) is pulse-modulated at a rate of several times a  second [most sources state 10 pulses per second],  sounding like a woodpecker. The radar was observed  using three repetition rates: 10 Hz, 16 Hz and 20 Hz.  The most common rate was 10 Hz, while the 16 Hz  and 20 Hz modes were rather rare. The pulses  transmitted by the woodpecker had a wide  bandwidth, typically 40 kHz.  Also in the 2000s on the HF bands, over-the-horizon  radars from other countries, using other pulse  frequencies, have been audible. The 10-Hz  Woodpecker was, and will be remembered as a unique  phenomenon that generated more interference  reports and speculations than any other radio  emission.  When it first began operations, the transmitter  interfered with several communications channels,  including emergency frequencies for aircraft on  transoceanic flights. Subsequently the operational  practice was modified so that the radar skipped these  critical frequencies as it moved across its operational  spectrum.  When the transmissions were first detected in the  West, some suggested that the Soviets were  developing a new radio system for communicating  with strategic submarines. Others suggested that it  was designed to detect and track low-flying aircraft or  missiles. Far less plausible theories extended to  suggestions the Soviets were trying to modify the  weather; experimenting with radio waves to control  human behavior; or developing a weapon to shoot  down nuclear-tipped missiles.  (source : ABM AND SPACE DEFENSE A. Karpenko  Nevsky Bastion, No. 4, 1999, pp. 2-47 and The Woody  Woodpecker Story by Väinö Lehtoranta)

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