The energy-saving LED bulb that switched off the radio

by , Senior Home Researcher Energy & Home 17 March 2013
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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?

An LED bulb lighting up the darkness

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.


Add your comments


malcolm r

I found the following on Voltimum’s website – just an extract:
“There are strict limits set on EMC for lighting products and most reputable suppliers test their products for compliance. The Lighting Industry Association (LIA) is aware of a number of reports of LEDs allegedly interfering with digital radio broadcasts and is in touch with both the BBC, which monitors this on behalf of the Government, and the EMCIA to establish just how bad the problem is.

………the LIA is conducting market surveillance on 2,000 LED retrofit lamps in its lab in Telford……”

I hadn’t come across EMCIA before – it is a UK Industry Association to look at EMC issues with its members – Delving into their site produced a link to what I thought was a very interesting document It shows what a mess there is, I think, and the disarray in taking resposibility for getting to grips with it.
Are Which? liaising with LIA and BBC on this problem? It seems to me that with the interest shown in LED interference this should be an active topic for Which? to follow up with other experts.


Gary M0PLT

It is nice to see an industry body taking note of the problem!

An easier to read version of the LED investigation can be found on the UKQRM Website:

The PDF was only intended for the EMC industry, and it lacks explanation. METECC kindly allowed UKQRM to reproduce their report with added explanation of the tests and their results. You can click on the images for a larger view of the test results. Some of them have the incorrect EN test listed, but that is academic as many of the limits are the same.

The EMCIA’s early work on the issue of non-compliance of Power Line Technology can be found on the Ban PLT website ( They, like UKQRM, have been raising the issue of non-EMC compliance since 2008.


malcolm r

More “work” from the EC who collated tests from member states on 168 LED products. 54% Chinese, 39% of unknown origin (!), 7% EU. These were tested against technical standards – emissions, immunity and harmonics – and administrative requirements – CE marking and Declarations of Conformity.
38% failed on emissions (EMC), 47% failed on harmonics, 9% were not CE marked. .In total only 17% met the technical and administrative requirements for them to be sold legally in the EU.
This work was reported in 2011. You wonder why no action appears to have resulted (or has it?). No product should be sold within the EU without a CE mark.
One way to stop those who disregard the regulations from importing and selling these products is to prosecute them – is there any sign of this happening?


Gary M0PLT

There is a conflict of interests stopping this. I have it on good authority from UKQRM members who attended meeting with Ofcom back in 2008. The “Men in Black” from DG Enterprises were present at the first meetings involving the issues of PLT. They spouted their mantra of “no barrier to free trade” and Ofcom were paralysed and refused to act. They continue to refuse to act, and whilst they are the Market Surveillance Authority (MSA) for EMC matters, nothing will change and junk electronics will continue to flood the market. If readers of this comments section have incurred costs and interference issues as a result of this, you must write to your MP and complaint. The issue of non-compliance can only be tackled by forcing the government to remove Ofcom and create a body who will enforce the law!



I have long advocated a spilt between the part of Ofcom responsible for encouraging trade and that for regulatory and enforcement aspects. There was a precedent for this within the CAA when NATS (National Air Traffic System) and SRG (Safety and Regulatory Group) co-existed. Both fell under the overall cover of CAA but were operated quite separately. They did not even operate from the same premises, NATS HQ was in central London and SRG at Gatwick (the visitors’ restaurant at NATS had the better view, though!).

Perhaps the MIB from DG Enterprises should have been asked how far their dislike of ‘barriers to free trade’ extended. Would they accept, for instance, the import of drugs or weapons on this basis? If not, where would they draw the line between acceptable and unacceptable illegal imports?



Noticed fm interference for the first time when changing to a single IKEA LEDARE LED bulb, two metres from bedside radio. Doesn’t seem to affect the DAB function though. Other websites have pointed to (some) manufacturers often skimping on harmonic suppression circuitry within the bulb electronics.


Dan Bown

I have been using Deltech 5W Mr16 LEDs as a replacement for 50W Mr16 ceiling spots for a number of years. I hve been unable to use them in areas near a DAB radio as they cmpletely cut out the signal. I understand the problem is made worse the weaker the DAB signal. I live in a modern reinforced concrete construction flat in London so receltion is not good. Thinking about how LEDs ork I am not sure if it is the transformers that work with them or the bulbs themselves. I have complained to Deltech who deny any problem.
More recently I have picked up the ;latest 7W Aurora LEDs from Amazon and they have the same problem so its needs sorting out one way of the other. I am trying to find transformer manuafacturers who have delt with the problem but no luck.



I bought these power supplies:
(not withstanding the names, these are 20+30W supplies)
+ 7 of these lights:

4 Watt MR16 LED Bulb – Wide Beam Angle Colour Option Cool White MR16-320-CW 4

I also installed a DAB external Ariel. (in loft)

When lights are installed in two bathroom ceilings. When I turn either set on:

1: DAB from the external Ariel drops off by a large amount (bubbling on sound , display show less than minimum usable signal)
2: DAB from internal Ariel stops
3: FM radio is covered in static (Radio4)

I installed ferrite cores on the “power supply” of one set (204V side + 12V side) to no effect.

If I’ve understood this correctly, the signal is produced at the bulb and is radiated via the 12V line acting as an Ariel. So if I install ferrite core very close to bulb (inside the IP65 enclosure) in each lamp, that should stop the radiation of the signal?



It’s probably the power supply unit that’s the problem.

Try disconnecting the LEDs and connect the PSU to a 12 V tungsten car bulb instead, e.g. sidelight or interior light less than 20W.

If you still get the interference, then you know it’s not the LEDs. If so, try installing the filter on the mains input to the PSU.



It is not possible to know the effect of adding ferrets – which autocorrect insists are ferrets. :-) I would be surprised if you are successful.

Gerry’s suggestion makes sense. Another suggestion would be to replace the LEDs with halogen bulbs, so that you can establish the combined effect of the power supply and wiring to the lamps at creating interference.

I cannot find any reference to radio interference on their website. I suggest you contact LED Hut to discuss the problem. You could ask if their products comply with the relevant legislation on EMC radiation. See Malcolm R.’s post at the top of this page.

DAB (and FM) aerials work much better if outside, rather than in the loft.



I’m curious why you need a DAB loft aerial. Unless the transmitter is in the next-county-but-one or there’s a mountain in the way, it shouldn’t normally be necessary.

Assuming that you really are in a very weak signal area, I trust that your aerial is vertical and just a single dipole (to make it omni-directional)?

Using a multi-element DAB aerial is usually counter-productive because, unlike FM, receiving all sorts of reflected DAB signals is A Good Thing: they happily all add up to make the final signal better. A multi-element aerial will be directional and result in weaker signals from any transmitters that happen to be in the ‘wrong’ direction.

Also, if the loft aerial or its downlead are anywhere near the LEDs or the mains wiring… :-(


Dave D

I keep breaking my own vows never to join in these convo’s again but anyway …..

I agree with Gerry about the download being near LED’s and associated wiring being a bad thing … and indeed being near to a great many other electrical appliances and their wiring too.

I don’t understand Gerry’s understanding that a loft or external DAB aerial should rarely be necessary ….. I live in what is suppose dot be a super-strong signal area for both digital TV and DAB radio – indeed I am in line of sight of the transmitter and it’s less than 2 miles away as the crow files, on the top of the next hillside, just about on level with my house – and yet I and all my neighbours had to have newer, bigger, many more element-ed aerials for our TV’s to work when the switchover happened than we had ever needed for analogue. (In fact with Analogue TV, most of the neighbours never had any proper aerial at all – you could get perfectly watchable TV with the aerial unplugged!) Similarly FM radio reception was amazingly strong with no aerial at all, until they started to transmit DAB as well – at which time I assume that they reduced the FM output power – and now FM needs an external aerial and DAB, even with an external aerial is completely un-listenable.
I know there are issues over being too near to the transmitter and in it’s shadow and so on, but I don’t think any of us here are in the ‘shadow’ as the transmitter is on the highest hilltop for miles around and we are on the next highest hilltop which is only about 100 feet less above sea level than the transmitter.
I appreciate that my post is about the nature of digital (useless) broadcasting rather than LED interference, but I assume (perhaps wrongly) that there is some link between the difficulty in receiving DAB to start with and the affect of LEDs and other sources of Electrical interference.
I’d be interested to hear anything that any aerial installers or radio engineers might wish to add to this convo.


Dave D

In 2nd para 1st line above for DOWNLOAD read DOWNLEAD … blasted autocorrect!



Decent external aerials are a great help for both good FM and DAB reception and one of the benefits is to minimise the effect of interference. Few would think of operating a TV without an aerial but even expensive radios often under-perform because they are never given a decent aerial. I don’t live in a weak signal area but have certainly seen considerable benefits from having external FM and DAB aerials. Owls wrecked my FM aerial and my temporary solution of installing a loft aerial has not proved nearly as satisfactory.

As Gerry says, it is important to keep aerial leads well away from sources of interference because there is only so much that the screening of the cable can achieve.



DAB Ariel is Basically this one:

I also have FM (radio) and UHF (TV) external Ariel.
When DAB was first launched , the little telescope Ariel was all that was needed, then after a year or so it signal dropped so only external Ariel work (my Postcode is RG45 6AL … it says I cannot get DTV , but should get DAB. There has been a lot of debate about this on Radio 4. All the ‘experts’ say DAB is better everywhere, then everyone phones in and says (like me) they cannot get a good signal. … but without the LEDs being on, the external Ariel shows a pretty strong signal, the display style is:

1 —-O—— (very strong)
2 —-O— (strong)
3 —-O (min to get good signal)
4 — O (sound will break up)

It goes from 1 to 3 as I turn on LEDs




>It’s probably the power supply unit that’s the problem.

Ruled this out using a suggestion posted here (on in avforum) I bought a 20W Halogen lamp (MR16)
1: removed 4 LED (4w) — no interference (probably no power either :-) )
2: Plugged in one 20W Halogen, no interference (power supply now under more load than 4Led)
3: added 1 ,2 and 3 LED (4W) … interference increases as they are added.



I went through similar pain (about which I posted much earlier in this conversation) -although I only bought the MR16 bulbs from LEDhut. I was using my existing transformers and just one bulb killed the DAB.

LEDhut never acknowledged that their bulbs were faulty -although I did get my money back on the bulbs, but only after an extensive email exchange explaining the distance selling regs to them. I had to pay for return postage as they said they weren’t at fault!

I won’t be shopping there again. However low their prices are.


David Farnell

I was hoping to install a DAB radio in our bathroom, unfortunately in 2012, I installed 12V 4W LEDs from a transformer, which killed the DAB reception up to about 10 metres away. I had to wait 12 months before I read that Philips 12V 4W LED solved this Which member’s signal problem. I have now installed them and as I swapped out each bulb with the Philips one, nothing happened to improve our reception, not until the very last bulb was swapped and then as if by magic the lights no longer affected any of our DAB radios!

We have 240V LEDs in the kitchen ceiling lights and these do not affect the DAB signal.

I posted this to Which but have not yet seen it published.


Bob Purbrick

I have spent some time on this and I can assure you that it is the chopped mode power supplies! I installed John Lewis under unit LED lighting and wiped out FM! I kept the lighting and bought better power supplies and can now listen to the radio!
I had a go with ferrite rings and ferrite sleeves and they really to help if you can be bothered!
I also installed JL kickboard lights and no problem at all and I have GU10 LEDs with no interference whatsoever.
Some manufacturers do not try hard enough to meet the CE regs!


malcolm r

Bob, I too used John Lewis under-cabinet lighting in a line fed from one end. I put a couple of DAB radios and an FM radio close to the driver, and to the LEDs, to test reception with no interference at all. I suspect these are the same LED sets sold by IKEA (4 lengths of white plus driver) – I wonder if anyone else has used them.



Bob and Malcolm – The last time you discussed these lights I suggested that interference may be being picked up by the radio circuitry rather than the aerial. In this case, one radio could be affected more than other models.




>I can assure you that it is the chopped mode power supplies

I cannot argue with you on this as I lack the electrical knowledge. However I did note here ==> that some bulbs only radiate above a critical voltage, so could it simply be the supplies delivered +/- 0.5V
[ and I have tested with same power supply but halogen bulb ... no interference ]



Just a few quick thoughts.

The DAB postcode checker suggests that in RG45 6AL you’ll get good DAB signals only on three multiplexes: BBC National (e.g. BBC 6Music) on Block 12B, Digital 1 (e.g. Planet Rock) on 11D and Reading (e.g. Pop Up Radio) on 12D.

So if you’re having problems with say, The Hits (London 1 mux, 12C), Jazz FM (London 2, 12A), The Arrow (London 3, 11B), Angel Digital (South Hampshire,11C) or Redstone FM (Surrey & N. Sussex, 10C) you must remember that you are outside their official coverage areas and any reception you get may therefore be iffy.

That said, LED lighting and power supplies shouldn’t generate interference and should be considered unfit for purpose if they do, especially if they affect stations that you can be expected to receive.



@GraemeV – try one of the Phillips MR16 LED Lamps from John Lewis . They are about £15 each but I was able to have the lights on and listen to the radio at the same time :) .

@Bob Purbrik – it’s to simplistic to say to say it is the chopped mode psu. The transformers I have work OK with regular halogen MR16 bulbs, they work OK with the Phillips LEDs , they don’t work with the LEDhut bulbs and some other Unbranded bulbs. I.e. It is an interaction between the transformer and some bulbs.

I should also add that all the bulbs I tried are claimed to be suitable for retrofit. They did the job of lighting the room – and some were even dimmable, but they killed the DAB….



I assume you mean this one

… oddly LEDhut offer this same bulb (and seem to be talking about an ‘upgrade’ :-) ) however it is narrow beam (36degreees) the bulbs I got are wide angle.



… oh not quite LEDHUT Philips bulb is 4.2W , John Lewis is 5.5W
(newer version?)



@GraemeV – I had to dig back through this conversation to find my posting: These are the ones I used that didn’t interfere with my DAB radio. I chose the bulbs on lumens, not wattage as its light I want!

Philips 5.5W MR16 Energy Saving LED 12V Spotlight, Clear

I also tried a dimmable bulb, again from Philips a MASTER LEDspot

Philips 7W Master Dimmable MR16 LED – Warm White (36°) from these folks

I haven’t checked if the links are current though..




Just taken delivery of 7 of the Philips MR16 bulb from John Lewis.
Tested a single bulb , it’s vastly WORSE than the LEDhut bulb. The LEDHut bulb reduces the signal. 4 LEDHut bulbs reduce it below minimum. The Philips bulb, a single bulb completely blocks the signal (unit reports no signal) . Retested with 20W Halogen , fine.

BTW, also tested with portable FM radio. Huge amount of noise from Philips , a Lots of Noise from the LEDHut, and some noise from Halogen (but only 2/3 feet away and only in certain orientations )

I’ve posted a warning review on John Lewis site (I’ll return the bulbs)



Wow, so sorry. Given my experience I had hoped it would be your answer. It just confirms that the problem is an interaction between the transformer and the bulb. I do hope JL are better about the return postage. It would be interesting to know you experience?

Out of interest did you buy the undimmable version?



Old_codger – That is an interesting suggestion that interference could arise from interaction between the power supply and lamp on 12V systems. If this is the case, perhaps manufacturers should specify use of their own power supplies if that avoids the interference problem.

Mains voltage LED lamps do seem to be a better choice for radio listeners, though I suspect that they might be more affected by premature failure.

I hope the next Which? report on LED lighting will provide useful information about radio interference.



John Lewis seem (right now, before I try :-) ) very good

I can just take them back to my local Waitrose (where I collected them) and they will refund.
I did not have to pay postage in the 1st place.

I did note however that the ‘review’ I added in the JS site has failed to appear , so far.

They only did the one bulb (not dimmable) … from the web site:

Product code : 70327012
Lightbulb Wattage 5.5W
Lumens 300

However the pack (Philips) details differ:

5W -> 325 Lumen (less power, more light)

These do not seem very “good” values BTW, The LEDHut bulb was 4W = 320Lumen … and was actually much brighter than the Philips bulb

The report seemed to make it clear it was (often) a critical voltage , so the power supply affects it. Also note they had one which was “good” but went “bad” the the voltage drifted [over time?]


Dave D

JL seem to be developing a shocking reputation for abysmal customer service lately – within the last month I know of upwards of 7 problems with their on line operation, branches in Surrey and Nottinghamshire, and my old bug-bear, the Sheffield store, where the staff are rude and, much worse, utterly ignorant of the products which they are selling. The experiences I’ve come across relate to fridge-freezers, computer related items and in one case furniture. Based on these reports, and the fact that their light bulbs (in the Sheffield store) are limited to a ridiculously small ‘range’ (Henry Ford would be proud), all of which are excessively highly priced, I’m afraid I would not personally try LED bulbs from them unless I was willing to accept that, faulty or not, I would not be able to return them.
If anyone does get LED bulbs form them it would be interesting to hear about the experience.



I have just had an interesting conversation with someone at LED Hut. Although radio interference is not mentioned on their website, they do know that some people have problems with their lamps and the power supplies used with 12 volt versions.

They were unable to give guidance on which lamps might be better than others. I asked if interference may relate to the manufacturers of the lamps but was told that LED Hut make their own lamps and sell them under the name Lumilife. I commented that in order to carry the CE mark, they lamps would have to comply with the EMC regulations. I said that I would mention this to Which? because I am concerned about products that do not comply with regulations.

I asked what would happen if I bought lamps and found I had interference problems. I was told that I have 30 days to return them. When I asked about return postage there was hesitation and the person I was speaking to said she would have to check. I said there should be no uncertainty because if the lamps cause interference they are not satisfactory. This time I was told that they are not faulty, even if they cause radio interference – so I would have to pay return postage.

LED Hut are aware of the recent Which? report about premature failure of certain LED lamps. I congratulated them on having a decent warranty – 5 years – and thanked the person I was speaking to for their help.


malcolm r

I suspect that LED Hut do not manufacture but distribute LED products. Their website refers to “manufacturing partners” which implies they buy from a number of sources. Not a problem – many do this – it just depends on how good those manufacturing partners are. As far as warranty is concerned I could find no proper terms and conditions on their website, so don’t know how they will honour a 5 year warranty. Can you point to it somewhere?
“Goods returned due to miss-pick, damage or failure should be sent Royal Mail 2nd Class Recorded Delivery as we will not reimburse any other method of shipment.” If returned within 30 days.



Malcolm – I’m equally convinced that LED Hut is a distributor rather than a manufacturer. I presume that their products are branded Lumilife, though I have no idea of whether this is shown on the lamps or just on the packaging.

The terms and conditions are at the bottom of the page, but do not refer to the 5 year warranty. The standard warranty is for 2 years, extendable to 5 years by registration. I believe that terms and conditions should be comprehensive and in a form that can easily be retained for future reference, for example a pdf file.

From the information on returns:

For faulty goods:

– Within 30 days of delivery we will always offer you the choice of an exchange or refund (excluding postage).
– Within 5 years of delivery, if there is a fault with your product we will normally offer a prompt repair, exchange or credit (credit to include original postage).

My comments:
– Why is postage not refunded if you have to return a faulty product?
– There is no mention of the need to register your purchase to obtain free repair/exchange/credit, or what ‘original postage refers to.



What they say and what they do are, in my experience, very different things. Their no quibble returns policy took 20 plus emails to just get them to honour their obligations under the DSR. Their case for not reimbursing me the return second class postage was that the bulbs were not faulty.

I assume to them radio interference is not a fault!!!!



It was made clear to me that radio interference is not regarded as a fault by LED Hut. It would be interesting if we could find out what other LED retailers have to say.



All of the experience here has convinced me that when I bight the bullet and replace the other 15 MR16 halogens here I will go the whole hog and switch to GU10. I now have several different types and none have the interference problems.

Is there any chance which could follow all this up with an investigation/report?

Hi, thanks for sharing your examples of LED bulbs interfering. Our researchers are still looking into it, and your experiences are essential in helping them do this.



This thread appears to have been truncated. I posted some results on the 22Feb . I now have a working setup. It appears to have been removed , along with all references to it (ie comments)
have you suffered a system failure?

Sorry Graeme, I see a few postings of yours with examples – if that’s not the one you’re thinking of, thanks for posting it again.



Just to add to the confusion :-(

I’ve now sent back most of LEDhut bulbs (and John Lewis bulbs) and today I received :
UF35B Noise Filter Ferrite Clip for 3mm Diameter Audio Vedio Cable 10 Pcs

Tried fitting these in my one remaining LEDHut MR16 (inside the lamp enclosure) … it seems to make some difference ….however:

The biggest difference came from the fitting (lamp holder). There are lots of overlapping issues here:
1: Physical location (rooms)
2: One is inside an aluminium shower enclosure
3: Make of fitting
4: Testing via external DAB, internal (portable) DAB, portable FM

… however the actual LED lamp is the same one (I only have one left)

This one , in the shower produces almost no interference (2 X DAB or FM)
Linolite Sylvania Round Low Voltage F-Rated Downlight MR16 IP65 White 12V

This one, in bathroom ceiling , produces a lot of interference :

The difference between them is the toolstation unit has a short flexible cable inside the unit
which attaches to the bulb ( acts as an Ariel?)
The Linolite has a rigid mount into which the bulb plugs.

(or it could just be the the “aluminium shower enclosure” which suppresses the interference)

I next plan to try : , which they assure me , do not suffer the problem.

In any-case, I’ll also test with ferrite cores



Lost postings: (this the gist of the posting I made on 22nd , which now appears lost)

I have a working setup, which is as follows:

7off these: GU5.3-250-W1-CW (
Powered (in two bath rooms) by:

30 Watt LED Transformer / Driver Perfect for Powering Sections of 12 Volt LED Lighting
TRAN30 ( )

20 Watt LED Transformer / Driver Perfect for Powering 12 Volt LED Lighting
TRAN20 ( )

PLUS I’ve installed these ferrite cores INSIDE the Lamp holders [ UF35B Noise Filter Ferrite Clip for 3mm Diameter Audio Vedio Cable 10 Pcs ]] ( )

AND these on either side of (one of) the power supplies (did not appear to help) ( )

These did not work:

4 Watt MR16 LED Bulb – Wide Beam Angle ( )

These were worse:

7 x Philips 5.5W MR16 Energy Saving LED 12V Spotlight, Clear (John Lewis) ( )


1: The lamp enclosure seems to have an effect (see my prev post)
2: Adding each LED Lamp seemed to show a slow increase in interference, adding the INTERNAL ferrite cores reduced this.
3: After turning on all 7 lamps , it was still possible to get a DAB signal, the level was lower by about 1 bar (prev was no-signal, or at least well below min level)
4: The big difference was WRT FM. A portable FM radio in the bathroom , was filled with static using the “old bulbs” as soon as I switched
to the new bulbs, it was clear. I could get interference but only by putting the Ariel withing 2-3 inches of the bulbs (previously detected
two stories below!)


Tim Mackenzie

Cheap mains-voltage powered LED bulbs may cause more interference compared to properly designed ones, but where a low voltage system is installed, the transformers can be the weak link from an interference perspective. Most modern transformers for low voltage lighting are of the “switch mode” power converter type whereby the mains power is rectified to DC, then “chopped” through an inductive winding to give the converted power output. The chopping frequency is normally around 40kHz with a pulse width varying at the required output frequency (50 / 60 Hz). The result of this modulated chopping is a series of radiated harmonics every 40kHz (40, 80, 120 etc). What this amounts to, is that the power converter is potentially a very effective RF noise generator. A badly (or cheaply) designed power converter will completely obliterate the AM band (500 to 1700kHz) even when operated within its specification. The electrical noise from the power converters is worsened by using LED bulbs on an improperly designed unit because the chopping circuit is forced to use too narrow a pulse width to maintain the output waveform. Having analysed the output from a number of popular power converters, it is clear to me that they are probably the greater source of RFI in such lighting solutions. However the interaction of the non-linearity of LED lights and their considerably smaller power usage, (which causes the power converter to be operated outside of its rated specification), exacerbates the problem of an already electrically noisy device.



My initial guess would have been that the miniature power supply inside “mains LEDs” would
be worse (due to size restrictions), however the opposite proved to be the case. The tests reported here:

Offer an explanation. The PSU drops 240VAC to 12VDC. The LED requires something lower (5V?)
this is achieved using some “cheap” on-board gadget (I forget the name and I’m not an electronic engineer) but this device seems to radiate when it’s fed an “over voltage” (e.g. 12.1VDC) and the critical voltage seem to vary by brand/item/age.

I did see somewhere that pre-built “sets” were much better (possibly because they could be built to work in series and so direct @ 12VDC) … but I guess the “Mains LEDs” don’t have the final stage? they are just to 240V to 5VDC (If I’ve got the 5V bit right?)


Dave D

Regulars know that I’ve had problems with both CFL’s and LED lamps – and not limited to radio interference.

However, I have recently discovered the BELL (British Electric Lighting Limited) range of G9 adaptors and both BELL’s 1.5w LED G9 Capsules (equivalent to a 40w incandescent) and the ‘MiniSun’ range of G9 Capsules (3 and 5 w, equivalent to 60 and 75w incandescents).

I have fitted these into many table lights and ceiling / wall fittings in my home, including ones where CFL’s had caused total loss of radio / TV signal, and also into exterior security lights, including one which is next to the VHF and UHF aerial downloads. There is absolutely not interference what so ever.

I therefore hypothesise that the issue arises with low voltage lighting systems, such as the infamous and ubiquitous 12v Halogen downlighter, when they are converted to LED.

I have no ideas as to why this should be the case, but Graeme’s suggestions above seem quite plausible.

I wonder if Wavechange has any ideas as I know he has a good deal of electronics expertise?



I think, I’ve given this info before (but I’ve noted this site loses posts)

1: I had 12V Halogen
2: Replaced JUST bulbs … these flickered AND one set (one PSU) pulsed on and off at about half second intervals … once they had “warmed up” (OK for about 15 mins) don’t know if these produced RF noise.
3: Replaced enclosures and power supplies … then started to notice the RF noise.

FYI: The ‘pulsing is, I believe, because the bulbs draw too little power
AFYI: The old enclosures were “open” at the back . The new ones are enclosed in a metal case (IP65) so I would have guessed the old enclosures were worse (but the flashing lights meant I never found out)



just had leds replacing halogens in the kitchen and thought I was going mad when the dab radio stopped even though the station still registered. This site has restored my sanity – now just have to solve the problem


Tom Oates

Have had a recent report of similar interference from a client causing his DAB radio to cease working when the LED down lighting circuit is on. Replaced with halogen MR16 all OK

A client on a recent project is using a high quality ‘retro-fit’ MR16 LED lamp by SORAA. After consulting with the manufactures of lamp, PSU and controller we have reached a conclusion that although each component may be tested individually for compliance with EMC regulations it is the combination in a circuit that results in problems. SORAA tested their lamp using shielded cables and recommend that ‘shielded cables or conduits that are earthed should be used with the lamp to avoid unwanted interference’ – hardly a retrofit solution !!

We are awaiting further advice.

Unfortunately is seems increasingly that each project has to be considered as a ‘one off’ and specification is a minefield of potential incompatibilty and other unforseen issues. Unless all main parties Lamp / PSU and Controls manufactures combine data to find meaningful solutions rather than testing in isolation the problems are not going to disappear.


John Dalton

I’m sure you’re right in your analysis, but SOME manufacturers HAVE achieved “retrofit” solutions that seem compliant. The MR16 LEDs I reported on in November, which came from Lidl and were remarkably inexpensive, cause no FM or DAB interference in my kitchen. I have three different HF transformers and two plain 50Hz transformers powering 11 of them and have had no interference whatsoever from them. Unfortunately, like most Lidl products, you can’t get them now. But it does show that it IS possible to design a replacement lamp that doesn’t cause interference.

The only problems I’ve had is flickering with one transformer (an Aurora, looks like all the others) but that was a low-load problem & didn’t cause interference. And two bulb failures out of the 20 I bought, which lidl refunded with no hassle; they’d gone dim, not dead, and cool white. These were Livarno Lux 5W (230 lumen) warm white GU5.3 and they only cost £4.50 each!



I think I managed to get some working. I had a problem with DAB completly cutting out but that is partly because I am in a valley with just about enough reception to get signal with the radio beside the window.

GU10/60SMD at

I have 8 of these in the cieling – before just a single Philips lamp would knock out my signal.

I also have a single floor lamp. I went with a PAR shaped bulb in an E27 fitting. This is because the bulb case is thick and acts like a shield PAR38/LN/18W It is 18W so pretty bright for an LED.

I also have some under counter lights so used a 20 Watt LED Transformer for powering 12 Volt LED Lighting

I took some advice from an electrician friend and installed ferrite cores inside the Lamp holders [ UF35B Noise Filter Ferrite Clip for 3mm Diameter Audio Vedio Cable 10 Pcs ]] ( )

All works well – I hope the above helps.



I’ve got this problem with LEDsave’s 1.5w G4 LEDs – 19 of them in a pendant fitting 2 or 3m from the DAB radio. No problem before with halogens or when I replaced a few of them with Maplins G4s (though the latter may be because it was summer and we never happened to use the light and radio together).
LEDsave offered a full refund as soon as I called them; they were familiar with the problem from a previous type of bulb which they discontinued because of it.
The Maplin ones seem to have been discontinued now, so I guess I’ll go back to halogens, as people’s experience of alternatives doesn’t seem good.



My own experience has been that the returns policy has some get outs. Most places won’t pay for return postage -that’s down to you. One even tried to deduct the original postage to me – illegally. After many emails they eventually refunded that as well.

Eventually decided to stop experimenting by post!

Sadly, it seems this problem continues to dog us DAB listeners and it was a surprise to see the DAB interference problem didn’t even get a mention in the magazine report last month.


Dave D

I can’t say that I have had the same problem with LED bulbs because despite what the relevant organisations say, I’m in a very poor DAB signal area (Digital TV is pretty rubbish too, even though there is no analogue anymore), so I don’t use a DAB radio.

HOWEVER … whilst slightly off-topic I can say that I have found that BELL LED lamps seem to be pretty good as lamps, but despite what their packaging states and what their technical support folk say, they are clearly NOT compatible with dawn to dusk photoelectric cells as I have fitted some into the outside lights an they fail within 30 seconds of switch on. This has happened with 4 bulbs after which I gave up and went back to tungsten GLS lamps (CFL’s are useless too, as documented at length in previous posts, as they fail after only a few days in summer and in winter won’t start up as they are too cold).

BELL LED lamps fitted indoors in fittings with just a standard switch work just fine and they have the advantage that they can be fitted with a huge range of screw-on glass covers which makes them suitable to replace almost every type of GLS tungsten lamp – candles, twisted candles, coloured, frosted, pearl, white, clear, globe, golf ball … you name it they do it. Really do recommend the BELL range to anyone looking to LED lamps for any BC, SBC, ES or SES fitting. Cheap too.

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