and this interfered with the VHF radios in the vehicles
Same thing happened to me, good point Marshall.

Anyhow that makes me recall an incident from long ago: Before low drift amps were available we modulated the input from the sensors of an extremely fast OCR reader (paper moving at 18 MPH) onto a ~600kHz (I do not remember exactly) ac. In a building in New York City the equipment refused to work and we were flabbergasted. Then, when scoping I saw the waveform and to my surprise, the probe was not connected. I found out that the equipment were located below the antenna of an AM transmitter at the same frequency. After changing umpteen capacitors to change the modulation frequency, the equipment worked.

Erik