A thousand different things from poor shielding in absolutely
anything and everything cheaply engineered that generates RF,
to RF traveling along cables - ethernet, audio, home wiring.
Maybe a dimmer, fluorescent light, poor ground on powerco
xfmr, cheap CATV amp, loose or improperly installed
cable tv cables, blah, blah, blah.
Routers and ethernet cables are super common sources of
interference along with loose or improperly installed cable tv
coax fittings. They spew out all kinds of noise.
The tough part is that it could be in any of your neighbor's homes, too.
If only on one or several freqs,
Have you put that freq in a handheld and done a walk around???????
Are you using a laptop or PC with UPS?
If so turn off the AC main at the house.
That will eliminate many possible sources.
I'd bet you'd find all kinds of ideas on how to solve
interference problems by using the search feature
in the RR forums.
It's been discussed hundreds of times.
Good luck.