[David]

Wall warts  can be a real problem things like power supplies for lap tops, phone chargers some LED lights and touch lamps. Try using a portable radio walk around your place and try and find the trouble makers. Have a touch lamp even turned off still sends out a signal in the air have to unplug the thing! High voltage power line near your place say 1 or 2 KM away can send out lots of noise over the air. During the summer storm season with a power outage thing are nice an quiet on the air waves and listening to a radio is so nice.