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The energy-saving LED bulb that switched off the radio

An LED bulb lighting up the darkness

We get sent some weird and wonderful tales of products going wrong, but one story piqued our interest so much that we just had to send it to the lab to test it out. Can you help us shed more light on the mystery?

Last year we received this intriguing message:

‘I recently changed six halogen down-lighters to more energy efficient LED bulbs. Unfortunately when the lights were switched on, the DAB signal on my radio was wiped out!’

To try and figure out this conundrum, we sent a batch of cheap, generic 12V LED bulbs to our lab and found that when a digital radio was placed within a few metres of the switched-on bulbs the signal went fuzzy. When the radio was placed within a few centimetres of the LED bulbs, it cut out all together.

The plot thickens

LEDs are ultra energy efficient light bulbs that can last up to twenty years and have been hailed as the future of home lighting.

It seems our members are not the only ones who have had this problem. There are other accounts of LED bulbs affecting radios, with AVForums also collecting stories. Nick Tooley shared his experience:

‘I had the same problems with LED bulbs wiping out DAB reception and tried several types of bulbs, but to no avail.’

And it seems that the issue may not just be limited to digital radios – TVs may also be affected. After fitting LED down-lighters in his kitchen, Jackord noticed the following problem:

‘While the lights are much better, we then by accident noticed that the digital TV would not work (I was complaining that we had no reception at all, did not make any sense, began to think that there had been some sort of catastrophic disaster which stopped the TV stations from broadcasting…lol) then someone turned off the ceiling lights in the kitchen and, hey presto, on came the TV.’

Shedding light on cheap bulbs

So what bulbs are affected? We tested three 12V generic LED bulbs and we also compared them to branded 240V GU10 LEDs and some halogens. We found only a very minor interference with our radio signal. So at this stage, the issue seems to be limited to cheap knock-offs rather than branded goods.

We’ve only done preliminary tests on this problem, so can’t make any concrete conclusions on why this is happening or how widespread this bizarre problem is.

That’s where you come in. We need your help – have you had this problem? If so, please enlighten us in the comments below, including what model bulb you were using and where you bought it.

Dave - TheRetiredPhyicist says:
28 October 2016

It is an inherent propert of a semiconductor PN junction (including the junction in an LED) , that it creates radio noise when energised(technically pink noise as the noise is not constant strength out to infinity, if it was it would be white noise). This is from the fundemental physis of semiconductor materials. And the only thing you can do is keep the aerials of TVs and Radios away from such devices. If commonsense prevails som time post-BITEX they will be banned and we can all revert to incadecent lamps along with coal fired power stations, and pull down all the eye-sore wind-mills now polluting the English skylines.


All well and good Dave but the large scale RF interference is being caused by cheap filtering and components in the SMPS , as well as deterioration due to overheating of passive filter components -C+R confined in less than ideal cramped conditions /noise generation of resistors/ capacitor ESR changing due to overheating , even exploding in some cases.


That’s different from the general view that the electronics in LED lamps and the drivers used for low voltage lamps are the source of interference. If the problem was semiconductor noise then why do some LED lamps produce severe interference whereas others create no problems?


Bang on Wavechange and he also says its pink noise , I am looking at a simple 70,s circuit diagram using a reversed bias zener diode as a white noise generator .


Do you know if a white noise generator produces frequencies as far as those used in FM and DAB radio, Duncan? I remember circuits for white noise generators when I was younger, but never build one.


Yes Wavechange but you need digital iC generators to amplify the circuits . I am looking at a 10Hz to 18Ghz broadband noise generator in the US commercial electronic engineering field but we are talking university test lab prices ( car prices or more ) . Under the conditions of an LED light there is nowhere near the power generation /amplification factor to make LEDs generate this , the LED,s are at the end of the chain of electronics not the input side which is the SMPS , they do not have the ability to act like a massive transmitter their junctions would be destroyed by a massive input of signal . If it was reversed and the SMPS with a large Mosfet was at the output fed from LED,s at the input which are amplified by the Mosfet -yes it could do this . Small circuits at 5 Mhz bandwidth can be built using zeners reversed biased not LED,s


It’s not Pink Noise (I’ve swept rooms with pink noise for equalization efforts) and it’s not White Noise. It’s just trashy, overdriven static being produced by a cheaply designed power supply.


I am not arguing with that Ed.


Some of us have been disappointed that Which? has not paid more attention to radio interference in their tests on LED bulbs. I am pleased to report that we have not been ignored and the April 2016 issue of Which? magazine has advice on how to get better DAB reception (page 58). This includes the suggestion: “Turn off LED lights”. 🙂

The other suggestions are more practical.