I replaced all the light bulbs in my house a few years ago with Cree brand LEDs from Home Depot. I immediately noticed that all 2m amateur reception on a hand held radio in the house disappeared.
After some experimentation I found the flood lights used in recessed ceiling lighting were the worst offenders and soon after I got a deal on a bunch of snap on ferrite cores with a #43 mix. I tried one, two and three ferrite cores around the excess wiring in the ceiling cans and three had the most effect and there was not enough excess wiring inside the cans to add any more.
With three ferrites on each recessed ceiling light in the house I can hear distant 2m repeaters again but I know there is still some interference generated by the LED lights. I also experimented with 2 turns of wire through a single #43 mix ferrite using a scaler network analyzer and inductance meter and found it does multiply the inductance and choking resistance by 4X, but the frequency that benefits the most goes from about 140MHz around the 2m amateur band to abut 70MHz and any benefit in the 2m band is negligible.
I think changing to a different ferrite mix like #61 and using 2 turns around a single core might give better results and someday I'll buy more ferrite and report the results. Using a different single ferrite core with 2 turns in my existing lighting will allow me to remove about 30 existing snap on ferrites to use on other projects.
prcguy
I'm just running through all the options that I can to eliminate as much artificial noise that I can from getting to my scanner and ran across this little article about EMI/RFI that is emitted because of LED light bulbs. I never would have thought about it, but it's right in the 30 - 300 mhz range. I replaced the ones that I had with cfl's.
So, if anyone else is experiencing the interference issues, read this.
LEDBenchmark - LED EMI Interference Issues