One of the ‘offenders’ in my area of “expensive last mile internet” is PoE where local ISPs may be using indoor grade UTP between their radio internet transceivers and the point of power injections. UTP acts like an antenna and power from dirty imported wall worts (switching power supplies) is very dirty (spectrally speaking.)

Had my ISP replace my UTP with STP and problem went away. However, when dealing with weak signals, the noise can be blocks/miles away and pretty broad spectrum.

Doug, N6UA