[ETS/PARC List] LED Interference

[Martin Minnicino]

I sent out a little primer on this issue a few months ago, but I cannot find it, so I will summarize again.

I too discovered this RFI problem with the new LED lights about three years ago when I upgraded all of my driveway lights.  Suddenly one day I had all kinds of interference on my radios, including the broadcast AM band.

Not all of these new LED lights are created equal.  You can purchase the simpler ones that contain only a rectifier, resistor, and capacitor that do not generate any RFI.  The more sophisticated models which (typically) have some complex surface mount technology tend to have some switching circuitry and/or more creative current limiters that creates havoc.

You have to experiment with the various brands and models.  I have a Sylvania decora candle bulb that generates no RFI, but the Sylvania regular base lamp version could be used to jam enemy radar...  If an LED bulb is to be used in "my" house, it must pass my very sophisticated laboratory testing procedure (I hold an AM radio up to the bulb and listen for noise).

As a rule of thumb, the brighter LED bulbs tend to have the RFI problem because they are driven harder and usually have the more complex power supplies.  Unfortunately, the manufacturers do not list this information.  You will have to experiment yourselves.

I too am amazed at what the FCC will allow to be manufactured today.  It is not like the FCC of years ago.  If you walk around your house with a portable de-tuned AM radio, you will discover about a million devices that produce a decent amount of RFI.  Even my digital toaster is a culprit!  And don't even get me started about my computer.

Hope this helps...

Martin Minnicino
WN2SJL


The following message was forwarded by another member of the Amateur Radio Club of the National Electronics Museum - I think you'll find it interesting.

A couple of weeks ago I posted a message on the reflector about 2 meter RFI that completely rendered the 2 meter spectrum unusable. While I got a few suggestions about common sources, this was something completely new to me at least.

At last the source of the RFI has finally been positively identified!

To recap, the wideband RFI centered on 145 MHz which began in mid-December was isolated to a specific house in Caldwell, NJ about 700 feet from my home. The RF level was about 20db over S-9, or nearly 1 millivolt, yes, "millivolt', at my receiver. It wiped out the entire 2 meter band as well as the lower portion of the public safety and aircraft spectrum.

While the RFI sounded like AC line buzz, looking at it on a spectrum analyzer showed a 20 MHz wide signal that swept and pulsated. PSEG (the local electric provider) was instrumental in first identifying that the RFI was wideband and close to the residence in question as I had determined from walking the area. I then used a 4 element, 2 meter yagi to positively identify the direction of the source.
I considered that the problem might be channel 18 leakage from Comcast cable, but that did not prove to be the case.

I was able to talk to the home owner who was very cooperative in working with me to find the source. I first thought that it was associated with TV usage but several tests did not yield the precise problem though the Comacast cable box and Samsung large screen TV were able to be heard inside the house on my Yaesu HT in AM mode but nowhere near the level I was seeing at times at my home. It seemed that when the homeowner was not home the RFI would disappear and in that case TV's were off.

Today, another test was made where the homeowner turned off all TV's and the RFI was still present. She then started tripping breakers and the RFI completely disappeared! It was now positive that the RFI was from something In the home. Further testing revealed the source as 9 LED lamps in the kitchen that had been installed in mid-December, at the time I first noticed the beginning of the problem.

The lamps were obtained at Home Depot, and are the Eco-Smart brand, MR-16 halogen replacements, and are rated at 50w = 8 watts consumption. Obviously this is going to become a really big problem, not only for PSEG as people bite the bullet and purchase these things, but it will also become a FCC issue as well, as they clearly exceed any radiated emission spec's for consumer devices.

For now, since we know the source of the problem, I am working out with the homeowner a plan to perhaps go back to the halogen lamps. This problem needs to be escalated to Home Depot, the FCC, and anybody else that should be notified before the entire 2 meter spectrum is lost to licensed users in this country and others.

So, if you are thinking about LED replacements as was I, it might not be the best thing to do or if you do, make sure you can return them or take up some other hobby!

73, Roger, NJ2R