I found out that my city, changed some street lights with a low energy  bulbs  similar to the curly Q bulbs for the home. These bulbs give off some strange noises and gives us havoc  among the ham bands.
I wonder how these ever got past part 15 on giving off spurious  interference.
Last year my wife and I purchase a new furnace system, When it was installed the dc motor gave off  interference, with the threat of reporting the manufacture of not being compliant, the furnace people replace  the furnace  with one that was at no charge.
The interference that gave off from the furnace could be heard  yards from my house, the wires  to my thermostat was the antenna. So perhaps if my neighbors were hams and I was not  I would have caused problems  for them.
Walking around with a ,A M broadcast radio is fun sniffing out these problems
Pierre k9eye