/ 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.

Joan Kemp says:
5 April 2013

I have a John Lewis ‘Touch to switch on’ bedside lamp and get radio interference from a new Sony radio (bought because the previous one also suffered from interference) – I also got radio interference from my old halogen bedside lamp. I’ve moved the radio a couple of feet away & it is better, but still very sensitive. My husband does not have the same problem with his radio a few feet away and it may be that reception on my side of the room is poor to start with – he’s nearer the window.

If you have poor reception to start with, then your radio will be more affected by interference. Some bedside radios are very poor – I gave away a Sony one. The interference could be caused by either the electronic switch (especially if it is a dimmer switch) or the power supply used to drop the voltage (unless the bulb uses mains voltage).

Peter says:
5 April 2013

I recently had three LED dowmlighters installed in our utility room, which is next to our kitchen in which we have a Pure ‘Move’ DAB/FM radio (about 4ft and a stud wall from the nearest downlighter). The DAB signal is completely lost immediately the utility room lights are switched on.

They are Saxby GU10 5 watt 240volt/ 50Hz bulbs. I believe that they cost around £7 each, which must rank as cheap, I guess. They DO however, carry the CE mark (see Nigel_Essex’s comments, above).

Robin Caine says:
8 April 2013

I have been professionally involved in EMC for about 30 years, the last ten retired. I smelt a rat when I started hearing these LED lighting stories and have now borrowed a suitable spectrum analyser (Avantest TR4132) to prove it.
The test set up was easy- we had a new entrance hall and bathroom built last year, similar in area and adjacent. Each was lit by 3 MR16 Halogen downlighters.
Because of a fire hazard the hall bulbs were replaced by LED plug-in replacements, from LEDHUT type MR16-4.5W-WW (12Volt)
I fitted a dipole to the analyser and checked DAB levels with respect to the nanlyser reference
DAB = -70dB
Turn on LEDs (three of them) huge splatter at about 150MHz, at -20dB
Replaced bulbs by original Halogens – WHAT? no noise discernible!!!

NOTE THAT the inverters are the original Halogen ones- wired into the 240v house wiring.

As I expected, the trouble is all due to the use of transformer/inverters designed for the much heavier load of the Halogen bulbs and they do not like, and have not been tested for, the much lighter load of the LEDs.

I’ve seen it all before, one definitely compliant commercial PSU in a frame of equipment turned into a sawtooth generator when loaded with a number of cards fitted with series regulators. (If you’re involved in such design think about it – the input impedance of a regulaor is marginally negative….)

Let’s get purpose designed transformer inverters for LED lighting and GET EVERYONE AWARE of the difference – then the problem will go away. IT’S NOT LED LIGHTING, it’s USING THE WRONG TOOL FOR THE JOB!

Thanks Robin, but now we are waiting for the report about what the spectrum analyser shows when you have the right power supplies installed.

It had not occurred to me that anyone would just replace halogen lamps with LEDs. I wonder what would happen if people with LEDs and the correct supplies decide to switch to halogens. Hopefully the power supplies are adequately protected from overload.

John Dalton says:
8 April 2013

I disagree. If a lamp is marked CE 12v 50Hz then it should be suitable for a plain magnetic transformer delivering 12v AC at mains frequency. I tried the bulbs I had with such a plain transformer. They were just as bad as with the halogen HF transformer (which I had not underloaded in my situation as I was careful to leave one 25W halogen in the daisychain so that the current was within the operating range of the HF transformer). I was amazed to find interference from the plain magnetic transformer. I was also surprised to see that the “proper LED driver” advertised for these 50Hz lamps actually has a DC output!!

John, LEDs are dc devices – best operated at constant current. Presumably they include a circuit that produces a dc output from your ac lv supply – this is likely to be the source of interference.

John – I am not so sure. Unless the manufacturer has specifically stated that the power supply is designed be used with LED lamps, then you cannot assume that it is suitable for this application.

Malcolm – As previously discussed, low voltage torches run from a DC supply (batteries) via a dropper resistor but I believe that most mains-operated LEDs use pulsed DC, so the supply is not constant current.

Wavechage – it depends upon the design of the power supply. It is the current through an LED that needs to be controlled; from a dc supply the cheap way is by a series resistor, but this absorbs power and reduces the efficiency of the LED. Constant current electronic supplies are less lossy. My understanding is that LEDs are rated for output at constant dc current; “high power” LEDs may be 1000mA or more. Dimming can be accomplished by pulsing, so altering the on-off ratio.


Yes – it’s called pulse-width modulation. I’ve built circuits using it, given lectures about it to masters students, and built switching power supplies. I think it is slightly confusing to refer to it as constant current. I’m very grateful that you told me how a white LED works and would love to know what circuitry is used in commercial LED lamps.

wavechange, for LED drivers good examples are those from Philips – http://www.lighting.philips.co.uk/subsites/oem/product_pages/xitanium_indoor.wpd.
For “professional” LEDs a good example is the Luxeon “Rebel” range.

Thanks Malcolm. What I’m keen to see is the circuit diagrams for what is in these sleek cases. There are circuits for LED lamps on the Web but all the ones I have seen are DIY rather than commercial products.

Mike says:
9 April 2013

If you google ‘LED driver IC’ you’ll find quite a few data sheets for the AC/DC and DC/DC driver chips with application circuit diagrams. One example is the dimmable Marvell 88EM8183. Other non-dimmable circuits are much simpler.

Thanks very much, Mike. Something I can relate to!

Maybe we will see enthusiasts dissect LED lamps and post circuits showing which chips and associated components manufacturers are using. That happened in the early days of CFLs.

andrew says:
8 April 2013

thanks robin for shareing your analiser results as a radio ham it is very interesting as the 2m band coners aporx 144-146MHz too close for comfort.

I hope radio hams will create merry hell about interference caused by LED lamps and other new consumer products, Andrew. It’s good to see mention of RSGB in the earlier pages of this discussion.

Gary M0PLT says:
8 April 2013

Radio Amateurs, Shortwave radio listeners, Citizens’ Band radio users, the Civil Aviation Authority, GCHQ, and EMC professionals have all be making noises about non-EMC-compliant junk since 2008, and earlier. Sadly, the public bodies have been muted, so it is only the “hobby radio users” and EMC professionals left who are raising awareness of the issues. Whilst Ofcom remain in a position where they can and do ignore their statutory duties, this farce will continue unabated.

Sam Wilberforce says:
8 April 2013

The dimmable LEDs in my kitchen are 1.2 m from the aerial. There are no noticeable effects on FM, but the DAB ( which is a weak signal at best) completely cuts out when the lights are on. The dimmables obviously have quite a lot of electronics with them, and have not so far been reliable – I have had to change 6 of the 7 over the last six months. Remember the old Philips bottle-glass compact fluorescents? I guess LEDs are still at that early stage.

It is very disappointing that your dimmable LED lamps have not been reliable, Sam. It occurs to me that the manufacturer may require use of a different type of dimmer from that normally used for incandescent lamps. If you have been following the instructions (or not provided with any) you should certainly return the faulty lamps to the retailer for replacement or a refund.

We have discussed the Philips ‘jam jars’ quite frequently on Which? Conversation. They used a modern triphosphor tube, cleverly folded into a compact shape. Otherwise, the technology was old and well tried, with choke ballast and switch-start. It was reliable and being devoid of electronics, the lamps could be put into unventilated enclosures (if they would fit) without danger of failure due to overheating. Undoubtedly large and heavy (around 600 g), but not bad for a product that did a lot to make fluorescent lighting acceptable throughout the house, rather than just in our kitchens and garages.

Rose says:
9 April 2013

That’s intriguing! It never happened to me just yet! My house is full of CFL and LED bulbs!

piet says:
9 April 2013

For the readers who who don’t know CE means Chinese export.

Mike says:
9 April 2013

That’s just what this discussion needs: a comedian.

Agreed, and I nearly posted that the comment was unhelpful. I think the real joker is whoever came up with the idea that self-certification has a place in CE-compliance.

The problem is the vast number of products in the market. The “safe” method is to have all products independently tested and certified (as BSI and other national test houses can do) and then quality audit the manufacturer. This is difficult for a major manufacturer with all the product variants involved, and would be overwhelming for test houses. Smaller manufacturers could not afford the cost involved.
CE Marking applies to many products, not only electrical. It depends upon the integrity of the manufacturer – many, even smaller manufacturers, have the proper test facilities to ensure their products comply with the relevant international standards; their Technical Construction Files should contain all the evidence and results of testing and are open to the policing authorities to examine. It is probably the only way that a workable system can operate but, like all things, ignorant or deceitful manufacturers or importers/distributors can cheat. That is why it is so important to have a reporting system for suspect products that can be acted upon . The key is to collect data centrally and know who will act on it – a job for a Consumers Association?!
A difficulty is that CE marking relates generally to existing safety standards; these can take a long time to develop, and technology is always ahead of standards.

You know more about this than I do, Malcolm, but I have learned enough to know that CE marking is little help to the consumer, especially since good and bad products, genuine and counterfeit, will all be CE marked. As you say, the range of products covered is very large. I cannot see that consumers organisations in the EU (or is it the EEA?) could possibly afford to do this, even as a joint exercise. The only viable solution I can envisage is for the manufacturers to fund the independent testing of their products. Controversially, I would suggest that part of the cost is paid for by fines levied on companies that break the rules. If all manufacturers are subject to the same rules, at least it is fair to everyone.

I appreciate your point about safety standards, but we need to find ways to overcome the problem as far as practically possible.

The design of the CE mark is defined in all Directives. Describing the concept is a little difficult without pictures, but I’ll have a go. Imagine two circles arranged side by side and just touching. The ‘C’ then follows the left hand semicircle of the first circle, the ‘E’ follows the left hand semicircle of the second circle with the horizontal line part extending to the centre of the circle. There is another variant often seen which is identical to the official version but the right hand circle does not just touch but overlaps the left hand one by half the diameter. The appearance is just like the official version but with the ‘C’ and the ‘E’ much closer together.

There was a story going round, sometimes from reputable sources, that the close-spaced version was intended to give the impression that an item complied with the EU Directives without it actually doing so. This variant of the CE mark was said to stand for ‘Chinese Export’. There is much doubt about the truth of this, the more reasonable explanation being that it is simply an error in the drafting of the sign. It has to be said, though, that the drawing of the authorised version is given in all Directives and is very clear and explicit so it is difficult to see how anyone could make such a mistake. I have now seen examples of the unauthorised version on quite a few items – they are easy to spot when you know what to look for.

piet says:
9 April 2013

Another disturbing matter with dab/fm reception (I’m sorry i was sarcastic) http://www.theregister.co.uk/2011/04/13/bbc_plt/

Graham Pickworth says:
10 April 2013

Following my previous comment on 21st March re my gu10 bulbs, I’ve been following this forum with interest. However, since my original comment I have been adding further led’s throughout my house and now have: 6 x gu10 6 watts in the kitchen; 5x 4watt candles in a chandelier, 2x 4 watt candle wall lights and 1x 4watt globe behind my tv, all in my sitting room; 1x 7 watt globe in my study; 1x 7watt globe in my bathroom; 2x 7watt golfballs in my bedroom; 3x 4watt candles in a chandelier in bedroom 2 and 1x corn bulb on the landing. None of these bulbs create any radio interference at all. Can anyone explain, in face of all the obvious problems, how I am so interference free. All the bulbs are 220 volt byh the way, so I don’t need any transformers.

M. Joshi says:
10 April 2013


Is that no interference to your Bose analogue radio, Roberts DAB radio or both?

Are all the LED lamps from the same manufacturer?

You haven’t mentioned your location – it’s possible that you are close to a DAB transmission site, hence you have good signal strength.

Graham Pickworth says:
11 April 2013

M Joshi,

I’ve tested the bulbs against my dab radio as the bose is a bit cumbersome to move. I only have 2 makes to give you and they are Aurora and Verbatim.The others were all unmarked. However they were all bought variously from: LED Lightsmart, LED Trade Counter, Lights For U, Strictly Lamps and LED Hut. My location is Surrey, about 3 miles from Kingston on Thames and near Hampton Court. I hope that info is useful.


Graham Pickworth says:
11 April 2013

M Joshi,

My location is Surrey, about 3 miles from Kingston on Thames, near Hampton Court. The bulbs were tested with my dab radio as the Bose is a bit cumbersome to move. Only 2 of the bulbs had a makers mark and that was Aurora and Verbatim. However they were all bought variously from LED Lightsmart, LED Trade Counter, Lights For U, Strictly Lamps and LED Hut.


Karsten says:
10 April 2013

LED’s are innocent, LED’s do not generate noise —– but
The switched mode power supply used to change the input voltage to the right current for the LED’s can generate a lot of noise. The solution is a noise filter between the mains voltage and the switch mode power supply. The brand names of LED light do add a noise filter, cheap China LED lamps do not. If you have a noise problem, then it might help if you add a noise filter yourself, needs to be installed as close as possible to the power supply, noise filters could be: http://www.corcom.com/Series/PowerLine/B/
In my work I often have problems with electrical noise and today switch mode power supplies are the worst noise generator — and as they are used for LED lighting, LED’s get the blame. The filters helps

Mike says:
11 April 2013

The filters that you have suggested are no doubt very effective in reducing conducted EMI in industrial applications. But there are a few problems:
They aren’t specified for attenuation at 220 MHz, so we can’t know how well they would work for DAB
They would be difficult to use safely in a domestic lighting circuit – not a DIY job
Wouldn’t the cost of fitting a filter exceed the cost of replacing a bad bulb with a good one?

Just to give a bit more information about my kitchen LED bulbs (which don’t interfere with my kitchen DAB when 1.3 metres from an Evoke 1), they are four Luminus GU10s marked “B-PUK2013 3000K 38deg 3.5W 230V 50Hz 30mA L11-57235” They do carry the CE mark, but it’s the mythical ‘China Export’ mark which doesn’t conform with EU stipulated geometry for the conformance mark. (I’m not saying that’s very significant, but it’s interesting that a bulb that appears to comply with EMC regs isn’t marked correctly.)

I have had LED bulbs fitted in downlighter fittings in my kitchen.When they are switched on the sound goes off on every DAB radio in my bungalow no matter what room it is in.These fittings are low voltage on individual transformers.My son has LED down lighters fitted in his kitchen on 240 volt mains and has no problems, this would seem to point to the transformers being the trouble.I am going to try ferrite clamps on each of the light fittings mains side of the transformers.As anyone else tried this solution I would like to know.

John Dalton says:
11 April 2013

I’ve tried ferrite rings with tow types of 12v MR16 type bulbs that caused me a problem on FM. I’ve also 3 lamps running from 240VAC (a 4W GU10 and two 10W floodlights, all cheap China imports) which caused no interference even only 20cm from the FM aeriel.

The MR16s caused bad interference with just one in a daisychain of 3 (ie. one 5W LED plus two 25W halogens on the same HF transformer) but I couldn’t get to the wires enough to try ferrites there. But the same LED bulbs also caused similar interference on a plain transformer giving 12VAC 50Hz with nothing but an overheat fuse in its electronics. That seemed to me to indicate the problem was from the 12V to LED current converter in the bulb itself. I tried many turns of the 12v cable round some large ferrite rings (given to me by the BBC when I had interference from the Rampisham Down 4 megawatt World Service transmitter just up the hill from where I lived ten years ago). I tried it at both ends of the cable, but without any improvement. If I held the transformer casing in my hand the interference reduced somewhat. I can’t explain this, but my experience so far is that 240V types are well suppressed but the 12v types are absolute rubbish.

You could try the effect of screening the power supply with an earthed metal cover. Before I get shot down by a safety officer, I’m not suggesting this as a permanent solution and anyone attempting it should be aware of the dangers of mains electricity.

John Dalton says:
11 April 2013

I thought of replacing all the 12v wiring with coax, as well as putting Faraday cages round everything, but it all seems a bit extreme just to change a light bulb! There is no problem at all using halogens with either of the power supplies (an I see now someone else has seen the problem from a smooth DC battery source!). Therefore the problem is coming from the LED lamp and almost certainly radiating from the 12v cable connecting it to the power supply.

Robin Caine says:
11 April 2013

I have been progressing this investigation and I’m not ready to go to print yet. However, I was wrong in assuming that all the radiation came from the transformer inverter. Early tests show that running the MR16 LEDs from a 12V Gelcell shows the same switching waveform – I haven’t measured the radiation yet. But I can bear out the difference between MR16 LEDs and GU10s at Band 2 FM . The diffrence is enormous, I put a ferrite collar on the GU10 mains wire (on the bench) and got about 10dB omprovement, but I had to put the FM aerial within an inch of the GU10 mains cable.

I’m wondering if the rubbish comes from the 12V cable from the transformer/inverter to the LED and will pursue this as time allows. Obviously this is very short indeed in the GU10 and is probably one stage rather than the two 240-12 Volt and 12V-LED stages. If anyone else can show this I’d be pleased to hear about it.


I am an electrician and have just had the kitchen refurbished and fitted Philips 6W dimmable GU10 lamps and have had no problem. BUT we also have had a new fridge with LED lighting and this interferes with both the wall mounted TV adjacent and the DAB radio which is a couple of metres away. You would think that Neff would have put suitable EMC protection in place, but perhaps it has not occurred to them to test the appliance for EMC radiation.

Skep says:
12 April 2013

I’m a retired physicist and have seen this.

It’s not the bulbs; it’s the inverters. It’s not just “cheap” LED bulbs. It’s compact fluorescents also.

In the United States, almost all HIGHER quality LED and compact fluorescent lights carry a govt. warning that they “generate and use radiofrequency energy, and may cause interference.” The same warning appears on microwave ovens, USB mass storage devices, and various wireless devices. The proper search terms are RFI ( radio frequency interference ) and EMR ( electromagnetic radiation ).

That’s the power inverter in the light — it’s job is to efficiently convert the battery voltage or mains voltage to exactly what the LED or high-efficiency fluorescent needs. That eliminates fluorescent buzz, flicker and eyestrain, makes the bulb last a lot longer, and makes the lamp run cooler and much more energy efficiently.

In a higher-grade LED flashlight, the inverter stretches battery life, prevents the bulb from dimming as the batteries weaken, so you don’t have to replace the battery until it’s actually dead. By regulating the voltage, the inverter improves cold-weather performance, so your flashlight doesn’t go dim when you’re changing a tire. ‘Smarter’ inverters are ‘rechargeable battery aware’, and compensate automatically for the somewhat lower voltage [ 1.2 volt instead of 1.5 volt ], so your flashlight bulb won’t dim. Smarter inverters shut off to avoid over-discharging rechargeable batteries, which ruins them.

These inverters are miniaturized versions of the switching power supplies used in personal computers, and in most hand-held devices that have microprocessors.

Some radio noise is inevitable in a wireless environment, and digital radios are designed to resist it.

However the range of the interference is normally limited to a couple of meters at most, so you can usually find a spot where the radio works, or plug in the lamp somewhere else. When you buy another device, you may have to move stuff around again.

If your digital radio won’t work anywhere you can put it, the radio noise may be getting into your house wiring, which [ depending on layout ] act like an antenna. In that case, you can get an inexpensive noise suppressor at Radio Shack, which plugs in between the light and the wall outlet. The box costs less than you save on your electric bill.

Sometimes the problem isn’t so much interference as weak radio reception — e.g. if you’re far from the station, or down in a valley, or behind overhead powerlines, or in a steel building. Sometimes you just need a better antenna — check whether your radio has screws on the back to attach an improvised wire antenna clipped to the curtain rod or whatever. Check whether your cable TV box has a take-off for radio, or whether your apartment has an outlet to a roof antenna. The more digital signal your radio has to work with, the better it can discriminate [ reject noise ].

High-efficiency hiking and camping lights also interfere somewhat with radios, but greatly improve run time, brightness, and battery life. Just use common sense.

For example, when hiking I use a high-end Fenix TK-40 flashlight, with an effective range of 250 meters — but knocked out my weather radio reception. The solution was simple — move the radio’s belt clip away from the hand holding the flashlight, or clip it to my hiking pack on the opposite side, so my body shielded the interference. In a tent, same thing.

All switching power supplies emit low-level interference, because they switch at low radio frequencies — which allows the power transformer to be miniaturized yet powerful for its size, silent, more reliable, and cooler-running ( so the electronics last a lot longer ). The miniaturized transformer uses a lightweight ferrite core instead of a heavy iron core, and greatly reduces the size and cost of the copper winding.

If you want to know if a light will interfere with your radio before you buy it, dig up an old-fashioned analog AM radio ( not a digital radio ), or a short-wave radio.

Take the radio with you to the store.

Analog AM radios are the most sensitive interference detectors; analog short rave radios are pretty good also in the lower bands ( e.g. 20 meter band, 30 meter band etc., or frequencies below about 15 megahertz ).

Hold the radio near the light you’re thinking of buying [ within say half a meter ], and tune around the band. If you hear buzzes and whistles at various places on the dial, which fades when you move it away, that’s the radio emission. As long as it’s short-range, there’s no problem.

If you DON’T hear any interference at all, that doesn’t mean the light is better — more likely it’s too cheesy to have an inverter. Crummy LED flashlights, for example, just have a 5-cent resistor — read the fine print and it says “declining brightness lasts 200 hours”. The LED bulb goes dim as soon as the battery voltage drops a little, and by the time the battery is two thirds dead, the flashlight is no better than moonlight. That’s a little better than nothing [ but not much ], if you haven’t changed the batteries in your glove box in 3 years. Get a decent LED flashlight and the newer alkalines with 10-year shelf life — and don’t let ’em bake in the glove box — heat ages electronics.

You should NOT judge LED [ or compact fluorescent ]lamp quality solely by whether it interferes slightly. The vast majority of LED flashlights are, to put it mildly, junk from a technical standpoint. If you find one that’s sensibly designed and does what you want, don’t let a little interference stand in your way — deal with the interference. I say that as an expert in electromagnetic [ radio [ wave propagation.

On the other hand, most screw-in compact fluorescents [ spiral light bulbs ] are pretty much alike in terms of light output, longevity, and energy efficiency — but watch out for those having ‘garish light’ like an ancient fluorescent from hell. If a manufacturer cuts corners on costs, they’ll generally use low-grade phosphors, which are as hard on the eyes after awhile as black-and-white TV light. ‘Warmer’ light is much easier on the eyes — but if you buy a no-name brand, that light may ‘bleach’ after awhile, and you find yourself reluctant to work or read around it — never install those where kids do homework.

Why don’t manufacturers shield LED lights so they don’t interfere? That would add significantly to the cost. A metal case would block the emissions, but a metal case is much more expensive to make than a molded plastic case, especially in handier shapes. There are radio-absorbing composites, generally only used on high-end compact cameras, digital voice recorders and such. The composite feels cool to the touch almost like metal, but it’s actually a metal-oxide ceramic.

It took me quite awhile to find a well-engineered LED flashlight. The ‘right’ components aren’t cheap, and therein lies the problem — you pay more for a well-engineered LED lamp because it saves money on energy / batteries, your bulb doesn’t burn out when you need it most, and it manages to work on ‘zombie’ batteries past their expire date.

If interference isn’t how you tell a crummy LED flashlight, then how do you tell ? Well, you unscrew the top to change the batteries, and a bunch of plastic parts fall out, which you then have to fit back together. The flashlight barrel breaks in half if you drop it less than a meter onto cement, and the edges ‘shred’ so you can’t glue them back together. Your light flickers because the 3 drops of rain that fell on it last week cooroded the cheesy slide switch connected to the even cheesier copper metal spring in the bottom.

The heat sink that keeps the LED from overheating — there isn’t any. The battery terminal is a blob of solder. The delicate little circuit board is mounted so that if you jar the flashlight, the batteries impact that little circuit board like a battering ram.

You show that to the manager of the store where you bought it, and s/he yawns in your face — the problem isn’t that the light sucks, it’s that consumers uncritically buy crummy electronics that suck.

By the way, if you’re looking for decent LED or compact fluorescent bulbs for use in the home, there may be a govt. subsidy program through a local retailer, which is generally a pretty good brand that’s mass-produced and not over-priced. When you buy a screw-in fluorescent, there’s not a whole lot of information to go on — same thing when you buy an LED flashlight or keychain light. That’s why I carry my tiny analog radio, ‘cuz the radio noise spectrum tells me certain things about the light’s design and circuitry.

For example, right down the street from me is the store-front world headquarters of BrightGuy.com, which has some pretty bright people picking which products they carry. So I went in, fiddled with the demo models, and found myself holding a tiny inexpensive keychain light whose circuitry sounds were music to my ears. It has continuously variable light levels, and runs for hours on a pair of 25-cent calculator batteries with a shelf-life of several years. But I only found it because its switching power supply ‘called out’ to the little radio in my shirt pocket.

I wrote this article so you folks wouldn’t start a witch hunt against well-intentioned LED mfrs. simply because they emit some static. For example, my Fenix torch isn’t “cheap” — it originally cost $ 150 — yes it puts out fairly heavy radio interference at up to 2 meters, mainly ‘cuz it puts out enough light on the high setting to flag down a UFO. Everything about it is well-designed — they even threw in 2 extra neoprene switch covers for when the original one eventually shreds. The circle of light is so perfectly uniform in intensity and color that I use it for a high-end photography light.

The only reason NOT to buy an LED flashlight is you’re walking through the grocery store, and you get tempted by an 89 cent flashlight designed to eat batteries by a company that pushes non-rechargeable batteries that pollute land-fills. So they sell you a cheapo flashlight with a tungsten bulb that only gets 3 % energy efficiency, and will be too dim if you put in rechargeable batteries that aren’t topped off. That’s a sucker ploy, but it works, ‘cuz most consumers don’t understand batteries or lighting — so they pay 3 times as much for batteries that misleadingly claim to last “up to 3 times longer” [ but only in high-drain devices like photoflash, which they’re not required to tell you ].

One other thing — if you want to upgrade to efficient LED lighting, don’t pay $100 for a chrome-plated ‘concept lamp’ like something from a sci-fi movie. In fact never pay serious money for any lighting designed by an artist — they don’t understand lighting engineering, and the vast majority of lamp shades are crimes against humanity engineering-wise. A good LED light or compact fluorescent should be a chunk of good engineering, period. You can’t fix a deficient LED spectrum with a tinted shadde. That just makes it worse. If the warm colors aren’t in the phosphor to begin with, the tinting just looks murky.

Lastly, a comment to the person whose radio doesn’t work after replacing all the light bulbs with LED onces. You’re not supposed to turn them all on at once — that kinda defeats the purpose of energy-saving bulbs, and yes it will block radio reception. The real key to efficient lighting is to put light where you need it, or reflect it there with light walls, recessed lighting, or spot lighting. If your room ‘soaks up’ light, a bucket of reflective paint or reflective ceiling tile is the efficient solution, or even reflective drapes.

Remember, light is a form of energy — pure energy, in fact. The human eye works best on a well-balanced spectrum similar to the natural light humans evolved in. That will determine how satisfied you are ultimately with the lighting choices you make. Your eye is a camera, and lighting is everything. So you don’t buy lighting by how your radio sounds. My radio didnn’t work very well in my computer room or in my instrument room — partly ‘cuz I experiment with products. So I ran an antenna wire for the radio into a ‘quieter’ location. Now it works fine.

J. Merrifield says:
13 April 2013

When I replaced the MR16 halogen downlighters in our kitchen with LED equivalents a couple of years ago I found the DAB radio did not work at all. I used Sharp MR16-1x3W. I would love to know of an LED bulb I could get that would not interfere with the radio. My LEDs were not cheap, and I have 6 of them I can’t use at the moment.

Apart form the fact that MR16LEDs cost more than equivalent GU10 version, you also have the cost of the transformer. As an electrician I have had serious problems with the MR16 set up especially with dimmers. One only has to read all about dimming these to see that there is no industry standard and conflicting information abounds even on main manufacturing websites. There are clearly many problems with using LED lamps as a replacement for halogen, and although dimming is a far more minor issue than interference, these things are likely to keep us electricians busy! Since I have fitted several installations of Philips GU10 without any problems, I think I will continue to stick to that brand given the comments on this conversation!

Mike says:
13 April 2013

It’s very significant that this thread is pointing the finger mainly at MR16s, even from reputable manufacturers. I suspect that there are two or three reasons why 12V MR16s are much worse than 230V GU10s.
It seems that a lot of GU10s have a large number of LEDs in series with a reactive ballast. This type of circuitry is essentially RFI free, but it cannot be used with high power 12V lamps, which must always have switching regulators.
Because the input current at the 12V bulb terminals is about 350 mA (for a 4W lamp) rather than 20 or 30 mA at 230V, conducted EMI is far more difficult to filter. But there is even less room inside the MR16 bulb for suppression components.
There’s still a possibility that lightly loaded electronic transformers might cause a problem when changing from halogen to LED MR16s, but it doesn’t seem likely to be the main issue.
The benefit of 12V halogens used to be a longer lifetime than GU10s due to the much more robust filaments. That advantage is negated by changing to LED lamps.
If you are considering replacing halogen transformers with LED friendly ‘drivers’ when you switch to MR16 LEDs, it might be worth considering just removing the old transformers and switching to GU10s. Of course you would need to change the lampholders as well, and it’s not a trivial job. But at least you’ll be able to listen to the radio with the lights on. Just a thought.

John Dalton says:
14 April 2013

I agree with you, Mike, it does seem the 12V supply is the crucial difference. But I never realised long life was the reason for 12v lighting, I assumed it was cheapness of fittings (no earths, no big creepage & clearance gaps, no cable clamps). Which unfortunately as you say means going to 240v LED lamps is fairly expensive because all wiring & hardware from the transformer down needs replacing (but still cheaper than replacing every transformer with a set of LED drivers as the manufacturers seem to be recommending).

I have found another “good” 240V lamp, for what it’s worth; a 7W LED under-counter strip light (looks like a 30cm fluorescent fitting). It doesn’t generate more than a faint buzz on the FM radio at 30cm from the aerial. This one is from Aldi, is marketed by a German company and has “EMC CE” boldly printed in big type below the manufacturer’s address, with a properly shaped “CE” graphic. Aldi item 85873, under ten pounds, and with a 3 year guarantee which is probably enforceable and supports a 20,000 hour claim reasonably since that would be 2yrs 4 months continuous use.

Gary M0PLT says:
14 April 2013

This website http://www.ukqrm.org.uk/ contains answers to a lot of the interference issues people are experiencing.

This very positively a site worth visiting. When on the site click the link to ‘lighting’ then on the METECC logo to read an exhaustive test report on various light units. It make somewhat horrifying reading! This is a subject that Which? should be taking seriously, not just about the LED lighting problem but emc problems in general and the way that OFCOM is complicit by ignoring the situation when they should be acting to protect the consumer rather than the producer.

Barrie P Spink says:
14 April 2013

I have recently built a new shower room and fitted halogen lamps 12 volt fed off the solid state transformers., to meet regulations on safety.
I bought some 12 volt Led lights and saw the driver unit which I did not like as it was cheap plastic and you could touch live connections with a screwdriver. The LED lamps said 12 volts so I just wired them straight into the 12 volt halogen circuit in parallel with the existing Halogen lamps . For reliability I have two circuits and two solid state transformers with some of each on either transformer. They seem to work well and have done for around 9 months now with out any trouble. Have I done some thing wrong. I don’t notice any Radio interference.
Barrie P. Spink

When our DAB radio is playing our local Radio Devon station, if I turn on the light (in the next door room) the radio cuts right out then comes back on when the light has warmed up. However, if I am playing another station i.e Radio 4 the radio is not affected. It’s a bulb type Osram Dulux El Longlife 15/41-827 made in Germany. If I turn on any of my other energy saving bulbs which are Osram Dulux El Unique 11W stick type there is no problem.
Another mystery is why sometimes the radio cuts out if someone moves in the room, then comes back on when they stand still, often someone else can move in the same direction but with no effect on the radio – have not tracked this down to any lighting interference, other times there is no problem.

The problem being caused by people moving around in the room is often an indication that the signal is fairly weak. Moving the aerial outside or changing it from vertical to horizontal, or vice versa, might improve the situation.

Oh dear! The latest edition of Which? contains a test report on LED lighting with no mention of the emc problems. It really is about time that Which? got its act together on this subject. ALL electrical/electronic equipments have the capability of generating electromagnetic radiation and, for that matter, being sensitive to it. It really is no good making a product a best buy if it wipes out all the local radio/TV receiving equipment or throws a wobbler when a nearby transmitter is fired up. Testing for emc capabilities, exported and susceptibilities, should be an essential feature of all electrical/electronic equipment evaluations.

Hi Tony, there’s actually a mention of this at the top of p47 including a link to Which? Conversation. The other good news is that we are still testing this problem.

Thanks for that info Patrick. I hadn’t thought to look at the CFL page! Can you take on my comment about emc testing af ALL electrical/electronic equipments being evaluated by Which? Weak signal reception is becoming increasingly difficult in built-up areas owing to the level of em radiation from a variety of sources, particularly plasma TVs and powerline data transmission systems. It took many decades to clear the rivers of the pollution caused in earlier times. We do not want to have to go through the same thing with the em environment.