"The Duga systems were extremely powerful, over 10 MW in some cases, and broadcast in the shortwave radio bands. They appeared without warning, sounding like a

"The Duga systems were extremely powerful, over 10 MW in some cases, and broadcast in the shortwave radio bands. They appeared without warning, sounding like a sharp, repetitive tapping noise at 10 Hz, which led to it being nicknamed by shortwave listeners the Russian Woodpecker." https://en.wikipedia.org/wiki/Duga_radar https://en.wikipedia.org/wiki/Duga_radar http://www.brogers.dsl.pipex.com/Wpecker5.html http://www.brogers.dsl.pipex.com/Wpecker5.html