/ 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:

‘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.

Biggles92 says:
26 March 2013

We experienced problems with our new smart TV remote control. We had the remote changed three times during the first six months we had the TV but kept having problems whereby the remote just would not work the TV. Eventually, an engineer came out and asked us what sort of bulbs we used in the lamp next to theTV. We told him they were B and Q low energy bulbs and he advised us this was what was causing the problem. He said the low energy bulbs transmitted some sort of signal which was interfering with the remote. He had recently seen an increase in this sort of problem which was directly related to these light bulbs. He told us to change back to the old type of light bulbs. We did and have not experienced any further problems.

M. Joshi says:
26 March 2013

By low energy, I suspect the person who came out was referring to CFL (Compact FLuorescent) tube lamps. These have been known to cause interference to TV remotes because some of them emit infra-red radiation which interferes with the signal from the remote to the TV.

This should be minimal with LED lamps.

John Dalton says:
28 March 2013

That’s really interesting – my parents-in-law have been having all sorts of problems with a Humax remote that don’t happen in my house on the same equipment. They have CFL lights, we don’t. The symptom they see is the set-top-box doesn’t respond or seems to respond slowly to repeated presses of a button. But nothing to do with LED lighting!

steveb says:
28 March 2013

I have witnessed this as well and have had direct confirmation that energy saver CFL bulbs emit IR during warm-up. I use a British Gas 13A trailing socket which is switched ON/OFF using any conventional Infra-red Controller (e,g TV, HiFi, DVD etc) by programming a specific button on the controller. When i switch on the CFL lights (2 x 11W wall-lights), the Signal LED on the 13A trailing socket flashes continuously for a few minutes until the wall lights are fully lit, During this time, it is usually not possible to switch the trailing socket on or OFF because of the high ambient IR produced by the wall lights.

This used to be a common problem when CFLs were introduced. CFLs emit much less infra-red than old fashioned light bulbs but is pulsed, which causes the problem. Manufacturers of remote controls managed to resolve the problem years ago, but there are still some poor remote controls on the market. As John says, it’s nothing to do with LED lighting.

Lane says:
26 March 2013

We couldn’t work out why our digital radio in the kitchen seemed to be malfunctioning – not all stations, just some – after working perfectly well for 3 years. We recently replaced halogen downlighters with LEDs manufactured by Deltech UK ltd. Now you can switch Magic FM on and off with the light switch, as long as the radio is on. Can anyone scientific explain?

Alex says:
26 March 2013

Probably down to signal strength differences. ‘Magic FM’ goes out on the London 1 local DAB multiplex. The transmitter powers for local DAB multiplexes tend to be significantly lower than those for the BBC of Digital One ‘national’ multiplexes. For example, my local one at Zouches Farm has 3.2 kW for BBC and only 0.5 kW for the London 1 multiplex.

So, it is likely that the weaker signal strengths succumb to the interference from the LED bulbs while the stronger signals have enough power to override the interference.

DAB tends to be very on/off with interference. The design includes some level of forward error correction which allows it to recover the digital signal up to a certain level of lack of signal or interference, but beyond a certain point it can no longer do the error correction, detects it is failing to do so, and thus switches over to silence.

andrew says:
28 March 2013

Yes i have come across this and similer interferance problems before allmost any lighting device that uses an active controle circuit ,energy saving lamps and or bright led lamps use high frequency switching this can produce unwanted radio frequency radiation knowen as electromagnetic interferance EMI ..Allthough this is harmless to humans and other animals it can cause interferance and or tempary (while the light is on)malfunction to radios and other wireless/WIFI devices .there are standards in place to limit the levels of radiation and controle the suseptability of other devices ie your digital radio .to this interferance it would appear that they are not allways efective. The RSGB and OFCOM are i beleve conducting tests on devices to assertain wether they conform to the regs or not and if anything can be done to inprove the situation. But i am not holding my breath for a quick solution. looks like you may have to change back to halogen bulbs if you are experencing a problem, or try another make of led lamp but that could get expensive without any guarntee of a solution. Incidently plasma tvs give out quite strong interferance in th HF radio bands which can be a problem several houses away..

hope this helps to understand the problem sorry if i sound like the messinger of doom

Prior to your article on April issue page 7, I had notice that after changing my 6 GU10 mix of halogen and energy saving bulbs to LED from LedHut), my FM radio, an older Bose was “buzzing” when the light was on. So not only DAB is affected, that said these LEDs are fantastic with a wide angle and warm colour.

ady cheetham says:
26 March 2013

I use a ‘pure’ digital radio on site and whenever I switch on my LED 18v Dewalt torch on within a couple of metre’s proximity, the digital signal weakens or gets lost totally.

Baffled as to why and i’m an electrician…
Not noticed it with any of my hundreds of LED downlights i’ve fitted though.

No-one has mentioned an LED torch causing problems. I have tested my LED torches and worklights (eight of them) and none interferes with DAB reception on my Pure Evoke-3 radio.

Yours is probably a rather larger torch – probably using the same battery as power tools. Do other LED torches cause the same problem?

My LED torch causes no problems. As it is dc powered and a cheap way of limiting the current through the LED is to use a series resistor, it may be this is the method used, so no ac to cause hf radiation?

That would seem to back up my comments about mains rated LED fittings. “ady cheetham”‘s torch has an 18V battery – so it has some (switching) power convertor to drive the LED(s) A LED torch with only 3 cells in it (4.5V) wouldn’t have the same sophisticated power conversion circuitry in it and so would not be expected to cause interference. Of course, I’m making a guess here about your torhces…

kidbrookekid says:
26 March 2013

Noisy LED’s not really surprising. Diodes when switched – that’s reversed then forward biased very quickly – give out interference. This is due to the fast switching speed which in effect abruptly stops and starts the current flow, this develops a sharp edge in the waveform which chucks out interference. It is common practice to put a capacitor across diodes to suppress interference.
I can only assume cheap LEDs are not suppressed.
It could also be a symptom of the power supply in the LED’s not sure how they are powered.

as “kidbrooke kid” says it’s down to the power supply. An LED works at around 2 to 3 volts. In order to get it to work in a “230 volt” unit, there has to be some integral power conversion. This will involve a switched power supply. My guess is that the cheaper units (either because of poor quality components or poor design) generate radio-frequency interference which can affect DAB radio receivers. Whether the interference is broadcast to the air or down the mains wiring is something that will hav eto be investigated.

B Maynard-Potts says:
27 March 2013

It’s not just digital radios or just cheap LEDs. I have a Sony ST-S700ES FM tuner (circa 1986, but with far better sound than digital radios). Its signal comes from one of those almost circular VHF aerials, mounted in the roof void, and connected with standard earth-sheathed aerial cable.

I recently fitted three Philips Master 8 W, 2700 K, 40D LED GU10 MV spot lamps, mounted, without dimmers, in fire-rated GU10 fittings in the kitchen, 3 – 4 metres from the radio aerial.

When these lights are turned on, the sound from the radio ceases or can just be heard, very distorted. When the lights are turned off, the sound returns as normal. If the LED lamps are replaced with compact fluorescent lamps, there is no problem.

Per Desi says:
27 March 2013

Just installed 12V LED bulbs in study and immediately killed DAB radio in room. Went and tested two other DAB radios from differential manufacturers and in different parts of the house, only to be surprised that it killed the DAB signal in these as well.

Call to supplier was gave the response that the bulbs are not faulty, try using radio with batteries, install shielding around radio, move radio……… Gone back to original bulbs and problem gone.

This area needs regulation – obviously current IEE regulations are not robust enough?

Gary Myers MIET MBCS CITP says:
27 March 2013

The problems described in the article are the tip of the proverbial iceberg. Manufacturers have been flouting the Electro Magnetic Compatibility laws for years, and the regulators (like Ofcom) whose job it is to enforce the law, are complicit in allowing them to do so. There is a rather perverse situation in many counties where the body charged with enforcing the EMC laws (Ofcom) are also under the thumb of the trade departments (BIS and DG Enterprises); the latter’s mantra being: “no barrier to free trade”. This seems to include the ability to allow manufacturers to ignore the laws which require them to place safe and compliant products on the market.

Since 2008, Shortwave listeners, Citizens’ Band radio users, and Amateur Radio users have been complaining of interference caused by the introduction of Power Line Technology – the chief culprit being BT Vision and the supply of the Comtrend PLT units. These devices fail the EMC Directives “essential requirements” and the standardised testing EN55022, and therefore should not be on the market. The campaign group, UKQRM, have been working hard to raise awareness of this issue, but have found authorities only too eager to promote PLT, and other RFI generating junk, at the cost of the radio spectrum. We have also found interference from switched-mode power-supplies (as used to power many LED solutions now affecting the general public), plasma televisions, solar panel mains inverters, Christmas tree lights, and now, LED lighting. When these issues are raised with Ofcom, they simply state they cannot act as the device is CE marked (does not prove compliance) and was considered “compliant” when placed on the market. Trading Standards have tried to get involved, but they lack the necessary EMC knowledge and defer to Ofcom, who pat them on the head, tell them it’s all OK, leaving them powerless to act.

You can read more of the shambles on the Ban PLT website: http://www.ban-plt.co.uk/

On the videos page, along with demonstrations of PLT causing interference and wiping out DAB radios, you will find an interesting video from German Radio Amateurs who have tested a number of leading-brand LED lighting solutions. Their tests prove that leading-brands are not always the best option!

If you have time to read the whole website, you will understand the chaos caused by the Technical Construction File route, the breaches of EMC law, the efforts Ofcom went to in order to hide the truth, and the PLT lobby’s efforts to obliterate the radio spectrum to suite their own ends!

If you would like help tracking down sources of interference (known as QRM), ask around your local Radio Amateurs. They often have equipment that can find noise and they have the expertise to advise you on best practices. Unlike Ofcom, they will not charge, save for a cuppa and a biscuit.

There is very good case for removing the regulatory aspects from OFCOM and setting up a separate organisation for this purpose, rather on the lines of the old Radio Communications Agency. There is a precedent in the way that the CAA used to be set up with the regulatory aspects in the hands of the Safety and Reguatory Group (SRG) and the operational aspects in the National Air Traffic System (NATS). These two organisations having quite separate management structures.

George says:
27 March 2013

Our FM (not digital) kitchen radio gets a hiss over the speech (to the extent that BBC R4, our usual channel, is almost unusable) when the LED spots are on. The three bulbs are Homebase GU10-fitting 6W (product code 396223). The bulb has a heavy finned metal heatsink.

One recently failed (much reduced light output) and I returned it. The Homebase Help Desk let me have a replacement 6W ‘TCP’ manufacture bulb, as the original one is no longer stocked. With one TCP bulb on, there is no interference with the radio. The new bulb is slightly smaller (good) and doesn’t have a heatsink. It’s also dimmable.

So my suggestion would be to look for recent-design bulbs that are regular GU10 size, are dimmable and don’t have metal heatsinks. The shelf price is around £10 – the same as the old interference-prone design.

LED lamps are expensive and the only way to be sure that interference will not be a problem is to test them in your own home. Perhaps ‘bring a bulb’ parties could be a new social event to help householders find out which LED lamps to buy.

How about a consumer body that highlights problems ahead of time and lobbies for better testing regimes? With financial penalties for stockists of official untested bulbs ….

At a grass roots level you could organise a pack of various bulbs and pass them quickly from member to member to familiarise people both with the problem and the answers!

It would be great if that was to happen, Dieseltaylor. It could avoid many dissatisfied customers and cut down the number of safety recalls. No doubt the problems are exacerbated by a desire to get new products on to the market as soon as possible.

Until that happens, I’m prepared to offer my services as a beta tester for LED bulbs.

John Dalton says:
28 March 2013

I tried posting a warning on BeamLED’s customer feedback site. The Swedish site operator threatened to remove my comments about radio interference because the feedback was supposed to be about the company’s customer service rather than its products. Took some careful re-writing to get the message across within the feedback site’s terms of reference!

JohnO says:
27 March 2013

We have 3 x 5w LED downlighter lamps in our kitchen as well as 5 older tungsten halogen (TH) lamps on the same circuit. The FM radio is unuseable on most stations with the lights on, this was not a problem with only TH lamps. The LED units are generic types purchased form Amazon, quite pretty and reasonably priced. The small inverter (240v AC -> 12v DC) that drives the lamps is model number HX-LED(4-7)X1W and are CE marked. They are also marked SELV (safety extra low voltage, i.e. they provide an isolated output.)
In other rooms we have GU10 lamps that do not cause a problem. These seem to have some form of passive voltage dropper/current limiter comprising a capacitor and other series circuitry.
I can only deduce that the active inverter units have insufficient RFI filtering and that the CE marking is “self certification” and no proper radiated interference measurements have been made.
This abuse of the system must be stopped in its tracks else we will all suffer in the end.

Surely Which? and its companion organisations are best placed to do controlled testing and to highlight regulatory as well as functional deficiencies to the relevant authorities, if there is perceived to be a widespread problem and non-compliance with EN standards. Consumers could feed their own experience in to a database to focus on the worst of the defective products?

The problem of interference is not confined to LED bulbs. As I mentioned in a previous post, Which? should be more active in protecting the E-M environment from all sources of pollution. It is particularly galling when Computing Which? recommends the use of power line data transmission systems. These are probably the worst of all devices in terms of E-M pollution.

Thanks Becky – looks like a serious problem. All CE marked products should be compliant with relevant EN standards, including EMC. Either the standards are deficient or they are being flouted. If the latter I would think the “authorities” need to take action, whether UK or EU. I am sure the Lighting Industry Association would lend their support – they should protect manufacturers who produce good products, and want to act against those importers who put substandard products on the market. Good luck!

Controlling street lights (switching and more lately dimming) by sending signals down the cables feeding them was largely unreliable because of the rubbish that distorted the supply waveform. Partly this is because in England and Wales most street lights are fed directly off the same cables that supply industry and housing – not dedicated cables – so they pick up all the distortions from their apparatus – e.g. motor drives. Presumably the same problems may affect computer data. Scotland partly had street lights on dedicated cables and was more successful.

The Radio Society of Great Britain (RSGB) has a department specialising in just this kind of issue. They have been aware of this one for some years and have tested a great many LED bulbs as well as other products which cause interference to radio services. All electronic devices have to conform to standards for EMC (Electromagnetic Compatibility); however, many products fail in this respect and it is a growing problem.

It may be advantageous for Which? to contact the RSGB at 3 Abbey Court, Fraser Road, Priory Business Park, Bedford MK44 3WH. postmasterrsgb.org.uk 01234 832700

ExEMCtest Engineer says:
27 March 2013

It is worth noting that as far as emc compliance is concerned, the “technical construction file” route to compliance does not require a test of the product I.e. does not need physical proof. It just needs a technically competent person to write a compelling case to say the product is likely to be compliant. RFI and sensitive receiver equipment do not coexist harmoniously. I suggest you ask one of the many UKAS accredited EMC test facilities to do an RF emissions test, concentrating on the receiver frequency range.

PeterT says:
27 March 2013

I have suffered similar interference from LED lamps for some time. Having tried all the makes available from the local electrical distributor I am of the opinion that they all are non compliant with the EMC regulations even if so marked. The authorities in the UK (Ofcom) are aware of this and choose to do nothing about it in similar fashion to the interference caused by PLT adaptors, CFL lamps and various low voltage power supplies.
We are being flooded with all sorts of electrical equipment that flouts the law and as there is no market surveilance in the UK choose to bury their heads in the elctronic smog rather than tackle the problem.
Those limited numbers that use DAB radios will suffer more than most as the DAB system is fragile and not suitable for modern use(its 30 yrs old !!)

Please, WHICH, will you take up the cause of making the authouities act against electrical equipment that doesn’t comply with the essential requirements of the EMC directive.

Marcus says:
27 March 2013

Had same problem with Hispec 3w GU10LED


For those who like to see the technical detail. It is interesting to see the inference that the lifespan of LED’s is very likely to be less than advertised

Light emitting diodes themselves are not the problem, but the power supply electronics circuits that are needed too certainly can be. Like much other equipment such as computers and plug-in chargers they incorporate a “Switched Mode Power Supply”.

( http://en.wikipedia.org/wiki/Switched-mode_power_supply )

These are now widely used because they do not need a heavy, bulky and expensive transformer working at mains frequency (50 Hz). Instead they use a system that converts the 230 V 50Hz to a higher frequency (some tens of kilohertz or more) which makes possible the use of a very tiny transformer and mall integrated circuit control system.

Traditional incandescent lamps supplied by the sinewave shaped 50Hz mains supply waveform draw a current with almost the same smooth waveform and almost no higher frequency harmonics are generated. Switched mode power supplies produce very rapidly changing non-sinusoidal waveforms that generate a lot of radio frequency harmonics.

In well designed switched mode power supplies it is possible to confine most of such potential interference by the inclusion of a mains supply filter inside the case so that high frequencies do not leak out into the mains supply cable. But inside an LED lamp this presents a very difficult problem owing to the very small space available, so that even the best designs are limited in effectiveness. It is possible that some non-approved lamps are sold which have no filter at all.

Compact Fluorescent lamps have similar problems but they appear largely to have been overcome in recent years.

Without getting involved in more difficult technical methods the best one can do is to keep the lamp as far away as possible from the radio and its antenna, even though that may be inconvenient.

I am rather skeptical about some predicted enormous lifetimes of LED lamps, and know of one case in my family. where in a kitchen ceiling they proved very short lived indeed. Low power LEDs themselves,as used in radios, clocks etc. can last a very long time; 30 years or more but an LED lamp designed to produce significant illumination has other failure modes. Lamps using as little as 5 W get quite hot especially when confined in small spaces. High temperature must seriously shorten the life of both the lamp and perhaps more particularly its internal power supply.

John Dalton says:
28 March 2013

If you look at the 1-star feedback to suppliers of LED lamps on Amazon you’ll see an astonishing number of early failures reported. I have no faith in the 25000 plus hours claimed by manufacturers. I’d be happy with a guaranteed 5000 hours IF THEY COULD SOLVE THE RADIO INTERFERENCE ISSUES!

Marko says:
27 March 2013

What’s the point of having Laws to protect the Consumer and the radio spectrum from products that cause Interference if those charged with its Enforcement i.e. OFCOM choose not to Apply the Law. There are Numerous products on the market that have supposedly Passed EMC tests and have CE stamps that cause Massive interference to radio reception and cause slow internet connections for some as the interference gets onto the phone line which then act like a Large Ariel. Products known to cause radio interference are Plasma TV’s, PLT Device’s (SMPU’s that little plug that charges your phone or powers your router e.t.c) Many smpu’s are fine and manufactured correctly cause no problems but that e-bay or market stall bargain may turn out to be a real danger. If the Law as it stands were being enforced correctly then we as consumers would not be having this debate or the problems be discussed here

John Dalton says:
28 March 2013

I agree wholeheartedly. There is no redress for the consumer except their right to a refund – no compensation for the waste of time and energy trying to sort out someone else’s negligent behaviour. Why have a General Directive on EMC at all, if it has no teeth?

Peter Knight says:
27 March 2013

I had 8 halogen downlighters in my kitchen. At the moment 3 are still halogen, 2 are CFL’s and 3 are LED’s. Since the CFL’s & LED’s were fitted (at the same time) it seems that weaker DAB radio signals cut out, sometimes dependant on where I stand in the room.
I am not sure whether it is the CFL’s or the LED’s that are causing the problem, although from what I have read it would appear to be the LED’s
The radio is about 3 metres from the LED’s.
The lamps are ‘Modo’ made by Megaman and are GU10 fitment, 220-240 volt 4.5 watts.