My favorite source of noise was a Korean fluorescent lamp with power factor correction (makes the inductive lamp load look resistive to prevent parasitic current flow in the power lines). It was square wave chopping the 120-240VAC=175-350Vpp input to the ballast at the plug with a variable frequency (100kHz-1MHZ) based on input voltage phase. A very simple circuit that efficiently coupled >1Wrms into a narrow band (~10kHz fundamental)swept square-wave into a 2m antenna.

I integrated the total power with a spectrum analyzer... but any radio I tested (including GPS, FM, WiFi & GSM maybe due to IF or saturation?) would stop working within 10ft=3m of the lamp. Driving around I could tell if the lamp was on using my AM radio (set to any station) due to the 120Hz buzz from several blocks away.

As far as I could tell it had passed Korean FCC equivalent, several tens of thousands were imported, and sold (at Frys at one point) around the country.

I destroyed ours, but sometimes, just driving around, I think I can hear one when I switch to AM.