So a friend of mine who lives off-grid brings in an LED MR-16 type bulb.... His issue was that when the LED bulbs are on, they completely wipe out AM, FM and weather radio reception in his place.....
He has one type, a warm white that he likes from Home Despot for $30, and a bluer type that he doesn't like, but that is 8 bucks delivered from a chinese source.
Both are to blame for this noise. Both are CE marked, which may be a simple "self-certified lie", at least as far as the EMI situation.
Whan I checked the 8 buck one out, it produced full quieting of an AM radio several feet away from the bulb and wires, completely wiping out a local AM station that the radio was actually tuned to..... all you heard was either near silence at the 550 khz end, or strong hash noise at the 1600 kHz end of the dial.
Investigation with the equipment here produced the information that it gave a strong wide-band noise output up to at least 5 mHz, which was as far as my easily-brought-in radios would go.
Interference with FM was also noticed, but not as strong. He plugs his FM radio into the 12V DC wiring at his place, which also runs the 12V lights. If he plugs into the inverter output 120v wiring, he has less problem with the noise, presumably due to the isolation between them.
These little bulbs apparently use a totally unfiltered SMPS to reduce 12V input (AC or DC) to 4V or so to run the LEDs.
At 12V input, they are as noisy as sin. With 9V DC input, they are pretty quiet, no doubt due to the variation of SMPS duty cycle with input voltage.
I intend to use the spectrum analyzer at work to check them out in detail, but even without that, I am shocked at the amount of RF noise this little 4W LED "bulb" puts out.
I had figured that OK, a capacitor across the DC input would probably do the job.....
Uh-Uh.... not even close. The direct broadcast noise, presumably from an inductor in the SMPS, evaded any line filters I tried, so that even though the DC lines were filtered and quiet, the radio still picked up strong interference. It took a pretty decent Corcom line filter to clean up just the wires, with no effect on directly emitted RF noise.
I do NOT like this....................
Here is the perpetrator..... known as an "LX051S"