Any smart appliance with a switchmode power supply or processor chip can do that, and CFL lamps have an electronic ballast operating in the 40 to 60 kHz range. Rare
that a CFL lamp would be that loud on harmonics unless very near the antenna or it's an older lamp going bad. Prime suspects would be anything large enough to radiate Q-5 (like a plasma TV) or something with a fair amount of wire it can couple into... Like a satellite TV box.
As mentioned previously, step one is to shut down your entire house to determine if the noise is internal or external. If internal (no power = no noise) bring up each individual circuit in your breaker box one by one until the noise returns. That should narrow down the source to a few devices. I know you checked everything in the house, but some things are easily overlooked. Like a porch light, nightlights, cable (or DSL) modem and router. The breaker box misses nothing.
If the noise source is external to you, think of this as a golden opportunity to learn the arts of direction finding by triangulation and public relations.