Those old Soviet over-the-horizon radars would cause interference here in the west, especially close to the borders where I lived. Sounded like a chopper.
Other interference memories is Soviet TV suddenly fading in and out on your screen.
Yes. That’s why Duga was known as the Russian Woodpecker, as it would put out a series of pulses on UHF bands that would (apparently, to someone who had never heard a woodpecker) sound like a woodpecker. This is probably what you were hearing, as it sounds more like a chopper than a woodpecker to me, too.
I grew up relatively near 'RAF' Fylingdales and the signal from the US BMEWS was so strong that it would interfere with listening to tapes because the tape heads would pick up the magnetic flux 'thrum.... thrum' of the radar sweeps, whenever you got within about 2km of it.