Turn off main house breaker. Radio must be on battery. If RFI stops, turn Main on and start turning off one breaker at a time.
If RFI remains and you can hear it on an HT go to fox hunting. Forums, Education, RWK Fox down load. Check your download file. If you can not do it with just an HT, remove the HT antenna. I you still can not locate it, go back to Forums, Education, RWK Fox down load, Below the down load is a PDF on building a beam for 445 MHZ, or you may have to build one for a freq that you can hear the RFI on.
Did you buy a new radio power supply? Did you put in a solar power system? If the RFI in intermittent, Take notes. It took me almost a year to find one that happened about 2 minutes twice a week. If you can not hear it on the HT, do you have a battery powered AM radio with S meter?