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I have heard of loose electric pole hardware vibrating in the wind and causing interference in the 400mhz range.

Basically they were looking to see if it was the source, and the guy banged the pole with a hammer, and the banging showed up on the listening station some 20 miles away.

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I've had a similar experience making an FM transmitter. I used a small air coil inductor that wasn't well secured to the PCB as part of the resonating circuit. My FM tuner would pick up ambient noise since the small sound vibrations would ever so slightly change the size of the inductor, modulating the frequency. Ceramic capacitors also have this problem. The small metal 'fingers' are susceptible to vibrations which change the plate distances, and thus the capacitance. Use your imagination to think about cases when this might be of interest for certain groups!

aka Microphonics.

The movement must have been diddling a flaky contact, causing sparking.

Most of the hardware on an electric pole should be grounded and the only attachment from the primary wire(s) to the pole is through an insulator or series of insulators.

That said, if there's a bolt on or near the primary, it's possible it worked it's way out and started mechanically vibrating making contact between some induced voltage and ground say.

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