[ETS/PARC List] LED replacement light bulbs and RFI

[Christopher Fine]

Hi all and looking forward to seeing you this evening!

Just sharing an experience with RFI, which might be useful if you encounter unexplained behavior that appears to result from RFI.

I recently installed an LED bulb - standard 60W replacement, decent brand - in my garage door opener.  This promptly impacted the performance of the remote transmitters in both cars.  I didn’t relate the two things at first, because it didn’t totally kill the system - just made performance highly intermittent.  I thought it was the batteries in the transmitters, so I replaced both sets.  The problem persisted.

I did some research online and found a flowchart for debugging garage door radio control problems.  Working down the flowchart, I replaced the bulb with an old-school incandescent, and the problem went away.  Further research revealed that the garage door opener manufacturers recommend avoiding CFL and LED bulbs.  There are certain types of bulbs that are stated OK, but only a few of the more expensive ones.

The openers operate in the range of 333 MHz.  The bulb sits close to the radio module.  I’m guessing the module isn’t well shielded, and nowadays the opener case isn’t metal on the sides.  So either conducted or radiated RFI could get through.  The bulb is right next to the antenna, too.

Moral of the story is - definitely this applies to garage door openers, but might be relevant to other environments too, like the shack.  I have no idea what the radiation coming out of these bulbs actually looks like, at least in the case I found, but whatever it is has enough nasty harmonics to impact a VHF system.  I’m certainly going to check for bulb-related issues if I encounter RFI in the home again.

QST had an article about this awhile ago, and they basically gave the bulbs a clean bill of health, but buyer beware: http://www.arrl.org/files/file/RFI/Light_Bulbs.pdf <http://www.arrl.org/files/file/RFI/Light_Bulbs.pdf>

Anyone else had this experience?

73,
Chris
KC2PI