/ Home & Energy, Technology

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:

β€˜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.Β Nick Tooley shared his experience:

β€˜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:

β€˜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.


Here is a Youtube clip of my problem shot four years ago.

The portable is on FM despite saying DAB on the front, and the ReVox tuner is fed from a four element roof mounted FM aerial. I realise the ReVox is out of the ark, but that model was once used by a HiFi magazine as the bench mark against which all others were tested. I suspect that there is little or no chance of improvement so DAB it is!

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Thanks Motco. That’s good evidence of severe interference. πŸ™

It would be interesting to know whether the tuner picks up interference with the outside aerial disconnected because it is possible that the tuner circuitry rather than the aerial may be picking up interference due to lack of screening.

You might be interested in the Convos about the forthcoming switch-off of FM radio, this one being the most recent: https://conversation.which.co.uk/technology/fm-dab-radio-switch/ Even early DAB sets could become useless with the migration to DAB+, although the BBC has shown no sign of doing this.

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Sorry for being a heretic but I have seen problems with lack of screening in expensive hi-fi equipment. The circuitry of my Hacker RP38A portable radio (definitely not hi-fi but quite expensive in its day) picked up interference from TVs and CB radio much better than cheaper radios. πŸ™

I think Motco has an A76 Mk II tuner, which should go on for a few years yet.

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I made the point that it’s not hi-fi, but I have seen interference pick-up by hi-fi separates. If Motco unplugs the aerial we can find out whether the interference is coming in via the aerial or the circuitry.

Of course interference would not be a problem if LED lighting complied with the relevant standard.

John says:
4 February 2022

Just fitted new Aurora (branded & v expensive bulbs) that have killed DAB radio within a few metres, when the radio is placed at the far end of the kitchen where there are no downlighters signal is fine.

Duncan, the problem is easiest to describe by likening the noise to the hiss that is heard on cheap FM tuners on stereo reception (but not on mono) especially with weak signals. The sound is hiss-free until the LED lights are switched on and then a very obtrusive noise starts.

It is an A76 tuner and I also have a B795 linear tracking turntable, and an A77 four track open reel machine. I was quite keen on sound quality before my ears aged along with several other faculties! The tuner is not quite perfect at the moment; the stereo decoder is not operating. I have a service manual but have not yet got around to ploughing through the diagnostics. I suspect the old electrolytic capacitor(s) may well be to blame. My enthusiasm for HiFi equipment is now much reduced so I have not spent money on equipment since I realised my hearing stops at about 10kHz (I estimate) and is certainly not improving. A DAB tuner provides a sound quality good enough.

Duncan has not been seen here recently.

I think you have been unlucky with your choice of LEDs. If they were simple bulb replacements it would be very easy to replace them with ones that don’t cause interference. The simplest variety use a capacitor feeding a string of LEDs, which is crude, has a lousy power factor but does not cause interference. High frequency switching drivers using inductors are more efficient but can cause interference if poorly designed. It’s usually DAB rather than FM interference that is the problem.

LED panels are more of a challenge, but if you took a portable radio to a lighting shop with a display you might be able to find a solution.

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In Duncan’s absence, a little clarification on FM stereo noise, and a practical suggestion.

The hiss on stereo and not on mono is characteristic of weak signal to the tuner. Stereo FM has a signal to noise four times worse than mono so requires four times stronger signal to be as noise free as the equivalent mono. I thus deduce that the LEDs are getting in either at the aerial or at least in circuits before the quadrature detector/stereo separator.

The LEDs or more likely the wiring to them could be broadcasting FM increasing the noise at source/diminishing the signal. If your mains wiring extends to the roof area near the antenna, then it is entirely possible that the high frequency goes all the way up there too. If you can get to the power wire to the lighting unit, try clipping a ferrite ring around it – as near to the light as you can reasonably get, Amazon actually do a range quite cheaply – search out “ferrite clip-on”. This will at least substantially reduce any copper-born radiation.

That’s a thought, Roger. Round here it is common for TV aerials to have masthead amplifiers, fed by a mains power supply. If Motco’s roof-mounted FM aerial is near a TV masthead amplifier it could pick up interference.

Sorry Duncan, I had not seen you post recently.

Agreed, Wave – and cheap mast head amps could be more susceptible – so likely worth a bead at that end too.

I have got a near-masthead amp wavechange (in the loft) but it is a long way from the FM aerial.

Oh well, best of luck with the ferrite sleeves.

Duncan, I admit that I am only an occasional visitor to these forums (fora?) but I am truly grateful for your interest and amazed at your in-depth knowledge of what was only ever a minority market product, and is now verging on antiquity! I should give more attention to the tuner especially as it seems likely that FM transmissions could be switched off in the medium term. You have aroused my interest again and I shall look at my service manual for values and locations and acquire a selection of components so as not to have a dismantled unit lying around while they are sourced. I also have a pair of ReVox (re-badged Beyer actually) headphones but the polyurethane ear-pads decay by hydrolysis into crumbs of dry dust. Replacements are available at ridiculous cost despite the brand more or less disappearing back into Studer, but like you, I rely on hearing aids these days and they are not really compatible with cans. Mine are NHS ‘finest’ Oticon digital aids set up by a delightful Polish lady named Agnieszka at Wycombe Hospital after an extensive audio survey of my hearing. You are right when you say that the range of frequencies that they enhance is far wider than my hearing has had for many a year. In fact it is like having my own in-built graphic equaliser in my ears! The idea that aids amplify is inaccurate – in my case anyway, they actually emphasise the regions of the audio spectrum that the patient has lost.

The turntable, like the tape deck, was remaindered stock so didn’t cost full retail price or I wouldn’t have either of them. A Sony shop in High Wycombe had the turntable in its window for some weeks before I decided it had reduced as far as it would ever do, and the deck was heavily discounted by a Tottenham Court Road HiFi shop when the B77 was launched. Nevertheless I suspect that if I totted up the cost over the years it might well exceed the figure you suggest. Fortunately I was quite well paid at the time – penury came later!
Thank you for your valuable help, I enjoy indulging in a forum that is not testosterone fuelled anger like one of the motoring forums I visit to feed my horsepower addiction. Too late I’m sure but may I wish you a belated Happy Christmas, and hopefully a timely Happy New Year.

Here’s a small Christmas present, Motco – a service manual with circuit diagrams for the A76: https://www.google.com/url?sa=t&rct=j&q=&esrc=s&source=web&cd=12&ved=2ahUKEwjp-9fZvs_mAhUVM8AKHevUA74QFjALegQIAhAC&url=https%3A%2F%2Fwww.vintageshifi.com%2Frepertoire-pdf%2Fpdf%2Ftelecharge.php%3Fpdf%3DRevox-A-76-Service-Manual.pdf&usg=AOvVaw2_M96KSXyTD93e_yIXu9BR

Back in the 70s it was common to supply manuals with Hi-Fi equipment or provide customers with them on request. Happy days.

Thanks wavechange! I have got a printed copy – somewhere… The downloaded one you kindly linked me to will save me disrupting the whole house looking for the paper copy!

Light bulbs emit radio waves, as not all the electricity is converted into visible light (radio waves and visible light are simply different levels of the same electromagnetic energy).

That said, problems with radio inference only occur with some but not all LED lamps. No other lamp types seem to suffer this problem. It follows that the most likely cause of the problem is cheap and nasty driver circuits, as opposed to the actual light emitting diodes themselves.

That is right Derek. However some self-ballasted compact fluorescent lamps also caused interference.

Radio interference from CFL (compact fluorescent lamps) was known before LED lamps arrived but was not a common problem. There were fewer manufacturers and presumably they took more notice of the regulations to limit the amount of radio interference emitted by products.

It’s difficult to know if a LED lamp has a cheap & nasty driver, as Derek puts it.

We bought two Meridian brand LEDG4/1.5WCLR bulbs purchased from Screwfix to replace two G4 Halogen bulbs under kitchen cupboards. As soon as we turned them on our Roberts DAB radio cut out. Changed the bulbs back to Halogens and radio turned back on. Suffice it to say we will continue to use the much less efficient Halogen bulbs.

There are some LED lamps that cause radio interference but in my experience the majority do not. I expect that Screwfix would be happy to replace them with a different brand.

It is impossible to play my Pure Evoke 3 dab radio when my portable LED lamp is switched on in the flat.

What sort of portable LED lamp is this, Sebastian? I have an Evoke 3 and a powerful rechargeable work light does not cause any problems.

It’s likely that your lamp does not comply with the electromagnetic compatibility regulations that limit the amount of radio frequency interference emitted by household products. It always helps to keep radios away from possible sources of interference, so having a bedside lamp and a radio on the same table may or may not work.

I have had my kitchen lights replaced with OVIA Omni Inceptor fire rated 7w (LEDs). The Pure Evoke-2 radio distorts greatly when the lights are switched on; most obviously on Radio Scotland but on other stations also. The same distortion occurs when the LEDs are switched on in the adjacent living room. We have tried turning the radio around, altering the position of the aerial on the radio and trying the radio in different positions within the kitchen.
The qualified electrician has tried ferrite cores on the cables in different positions, but this has had no effect.
Both he and his company are baffled by this.
Is there anything else we can try?

Hi Sue – LED lighting should comply with regulations that limit the permissible radio interference, so there should be no problem unless a radio was very close, for example where both were on the same bedside table. The source of the interference is likely to be the ‘driver’, in this case an odd one that allows the colour temperature of the lamps to be changed. I suggest that if you paid for the lamps to be fitted you should ask the installer for them to be replaced with ones that are ‘fit for purpose’ under the requirements of the Consumer Rights Act. If you fitted them yourself, you should ask the retailer. The manufacturer – Ovia – has no legal obligation unless you bought the lamps from them, but some manufacturers can be very helpful.

If you have a weak radio signal, this could be improved by having an external radio aerial fitted, removing the extendable aerial on the Evoke-2, and plugging-in the aerial cable.

Agree with Wavechange.

I’ve just looked at the product data sheet. It proclaims various approvals for, eg, waterproofing, acoustics and insulation for fire rating – all laudable – and proudly displays the CE mark bottom right suggesting that the design has undergone – and passed – rigorous tests for RF emissions and susceptibility. Similarly your radio has undergone tests for emissions and susceptibility. There should be “clear water” between them so that neither one should affect or be affected adversely by the other.

Do you have dimmer switches for these bulbs, either individually or in clusters? If so, temporarily you might ask your sparky to install on/off switches instead. If doing that clears the problem up, the dimmer switch may be the problem – might actually need a half decent dummy load. Maybe one “proper” lightbulb as well?

That’s a good point, Roger. Older dimmers designed for halogen lighting are often unsuitable for use with LEDs and can cause flickering, erratic behaviour, and can interact with the driver to create interference problems, though I have not experienced the latter problem.

Thanks for your thoughts. The problem is with the radio and LEDs in the kitchen ceiling (not a bedside table & radio ‘wavechange’). All the electrical work has been done by the same qualified electrician within the last year. The kitchen lights are in clusters of 3, each operated by a new on/off switch.

Thanks. The LEDs are in the kitchen ceiling & are in clusters of 3 operated by new on/off switches. The same electrician has done all the work within the last year.

We have also experimented with another Pure radio in another room. It too is affected by the same interference when the LED ceiling lights are turned on, regardless whether using an on/off switch for a cluster of 3 or a dimmer switch for a different cluster of 3.

Sorry everyone, somehow I seem to have two names Sue and Allthefamily (don’t know how to get to just one). It is the same person posting re the radio interference & ceiling LEDs.

Hi Sue and family! I’ve spent some time investigating radio interference by LED lamps since this Conversation was launched in 2013 and there seem to be fewer problems. Unlike many of the problems reported, your LEDs are not the typical cheap ones of dubious quality. I hope you can find a solution.

When I mentioned having a radio and lamp on a bedside table, that’s just a worst case scenario because interference decreases rapidly with distance (the so-called inverse square law). The further they are apart the better and since you mentioned interference from LEDs in another room you obviously have a severe problem.

Hi wavechange

Thank you for your investigations. No one at our local electrical firm has ever come across this before. They contacted the LED lights firm, but with not much progress. Attaching a high quality ferrite core seemed a promising lead, but that didn’t work either.
Appreciate your comment & explanation about a radio & bedside lamp too.
It seems as if we have tried everything so far.

Is it back to candles on the kitchen table in the winter months so we can listen to the radio?

We do have LEDs fitted underneath the kitchen cupboards, there is no radio interference when they are switched on.

Will Stewart says:
15 December 2021

I have bluetooth hearing aids which switch on and off continuously if I am standing near ceiling lights with led bulbs – they play a few notes each time and it drives me mad. It only happens in one room despite other rooms also having led bulbs. A recent additional flush ceiling light fitting in the problem room may be the culprit

Unfortunately there are products that do not comply with regulations that limit the amount of radio interference that electrical products emit. Hopefully the problem is with one brand of LED bulb and switching to another will remove the problem.