If you live in an urban area RFI source discovery is a pain. I have worked with neighbors and the local AC power utility to eliminate most of the RFI generated by dirty power insulators, bad connections, neighbor's TVs, hot tub equipment, light dimmers, touch panels, etc. I was surprised how many AC main distribution panels in older homes have bad or even floating "grounds" and buzzing breakers.
I was frustrated by one final constant source that I could not find that was "20 over" on all the HF bands and into 6-meters. I finally took my own advice to others and ran my station on batteries and then shut down, in turn, each of the breakers in my own house. The spaced RFI signal remained. I finally pulled the main disconnect and the noise went away! I finally remembered a small 2-circuit spaniel out in the gargage that was installed by the previous homeowner. When I reset the main and then tripped the breakers in the garage panel the noise went away again. I could not find anything plugged into the panel circuits except for the garage door opener and disconnecting that had no effect. I was stumped.
The following weekend I was digging through a large built-in cabinet in the garage and behind boxes was a battery charger for a cordless drill that the previous owner had forgotton when they moved. A duplex outlet was in the back wall of the cabinet. A battery was still in the charger. I unplugged the charger and that afternoon when I turned on the rig the RFI noise source had disappeared! Ah-ha! I went out and plugged in the charger in and he noise returned.
So, now I check every battery charger I have and half of them cause RFI! When I checked the 25 amp /13.8 vdc Radio Shack power supply I had just bought to power my rc aircraft LiPo charger on the bench, it wiped out most of the HF bands.