[squarefoot]

Radio interference from switching voltage regulators, power supplies etc. is normal as most of them work from several hundred KHz to above 1 MHz generating PWM square waves whose harmonics fill the spectrum up to hundreds of MHz and beyond. They're circuit-wise very close to RF transmitters, so it's a normal behaviour. The RF junk they produce however can be filtered out both by putting them behind good screening and by filtering both their input and output lines. This cost money though so cheap ones will perform much worse, and some of them don't employ any method at all to reduce interference.

[kurthr]

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.

[retSava]

Did you report it to the FCC? I understand if you didn't, as a consumer, and this is not an attack on you. But this kind of thing should be punished, and one of the main ways to do this is to bring this to the attention of the regulating authorities.

We can only keep the spectrum in good shape by, as a producer or designer, test and design to comply. As an importer, require and check certifications on what we import. As a consumer, report when we find something being funky. (again, not blaming you)

[TeMPOraL]

Change "buzz" to "scream" or "whisper", and this would be a great horror story...

[mark-r]

Any device operating at those frequencies should have an FCC sticker, meaning they've been tested to make sure radiated RF is below some legal limits. If the cheap devices don't have the sticker or have a fake sticker or were materially changed after passing the tests, they're illegal in the US.