When working for an ISP I was told a story of a huge amount of noise getting into the system sporadically on a node in a neighborhood. Happened during a certain time only about once a week and only for about 15-20 minutes. They finally tracked it down to some guys electric weed wacker. They bought him a brand new one and took the offending one. I guess it was bringing the service to its knees every time he used it.
