/ 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.

Prius owner Hoffman Estates, IL says:
24 September 2017

I have a 2014 Prius C that uses standard halogen bulbs for the headlights. About two years ago I upgraded to a set of LED low beam bulbs. They were 4-Phillips-Luxeon 45 WT 4,500 Lumen bulbs that were powered by the standard H11 12V connector. There was no additional power supply between the LED bulb and the 12V connector.

When I installed the LED bulbs, I noticed that when I turned on the LED headlights I Lost several FM radio stations that I like to listen to. Turned the lights off, and the radio stations were back on. This is the standard FM HD radio that comes with the Toyota Prius C with the standard stubby radio antenna on the rear of the roof. OK, I started listening to a collection of music on the USB port, so no big problem.

Yesterday, my driver’s side LED burned out. Now I have choice of selecting a new set of LED bulbs. I noticed there are some LED bulbs that have power supplies between the 12V H11 connector and the LED bulb. Does anyone have any suggestions for my new LED bulb purchase that might return my distant FM stations when the headlights are on. Thank you.


Prius owner-There is no need for voltage conversion at a 12V DC input Led,s are okay at that voltage, its the current drive that counts . Led,s are arranged In a circuit that equalises the current but they are susceptible to over current/voltage . What you might have seen as “power supplies ” would ( in a automobiles case ) be surge suppressors which look like “supplies ” maybe incorporating blocking for re-entrant noise/RF interference from getting back into the battery supply and hence your radio .On the other hand IF it is RF Radiated via the air then you will need to suppress the radio with an earthed metallic covering and up rate your co-ax to the aerial making sure the outer braiding is well earthed . Two different types of possibilities .


Duncan – I expect that the power supply used with some LED bulbs is there it stabilise the voltage to maintain constant brightness and possibly to prolong the life of the lamps. When the battery is being charged the voltage can rise to approaching 15 volts.


Wavechange -did you not read my post staying -“surge protectors” they can incorporate stabilisation using zenner diodes etc . IF you are talking of full blown stabilisation power supplies then that is very costly and quite large even in this day+age. surpassing the cost of the bulbs.


I take your point about surge (voltage spike) protectors but I was referring to voltage stabilisation. I have no idea of the costs involved. I agree with your suggestion about screening wiring.

Prius owner has mentioned obtaining new LED lamps. My suggestion would be to explain to the supplier that the lamps must not cause interference. If there is any problem then it should be easy to get a refund.


All my own build power amps+pre-amps had fully stabilised power supplies . The supplies had to be of the same high calibre as the amps themselves . Obviously it was all discrete analogue . they did not require much in stabilisation unlike the plastic modern SMPS stabilised versions which in my book are vastly inferior in an top end hi-fi setting. . You could get away with it in a small current pre-amp but not in a high power amp if it is run in Class A . Good amps had small value compensation capacitors usually polystyrene or polypropylene using high quality plastic not the cheap bin liner quality . They weren’t cheap to buy in very low loss types at high voltage dielectric absorption ( polystyrene ) = 0.00001@100Mhz they cost the earth now.

Old Fogie says:
27 October 2017

Bought “Lumilife” LED direct replacement bulbs for 50W halogen GU 5.3. Worked with existing 12v AC supply and light output good. Did not notice problem until darker mornings when lights in bathroom on at same time as morning radio alarm. Then FM radio signal completely drowned out by “white noise” interference.
Tried adding Ferric Chokes to lamp LV supply but no improvement. Did notice that Philips bulbs with higher light output did not affect radio. Spoke to supplier who said this ws normal fo LED bulbs and nothing could be done except moving radio further away. (Not possible because already on opposite side of bedroom from bathroom.) Tried experimenting with aluminium foil shielding around base of bulb where rectifier situated but no difference.
Then moved aerial for radio and suddenly no interference.
So if you have issues with LED bulbs affecting FM radio try moving/adjusting the aerial or even rotating the radio.


As you have found out Old Fogle the modern day “cure all Ferric Chokes don’t work with radiated interference of as high strength. While you tried the dodge of tin foil , which I hope you earthed , a better answer , if you could get it would be mu-metal. The higher the radio frequency transmission of a signal to your radio like FM and above the more directional it is this is exacerbated by universal use of Ferrite Rod aerials . Gone are the days of long wire aerials which are more multi directional. and which can be tuned by small value aerial capacitor’s have found that it is possible ( depending on the SMPS circuit for a heavier load to actually reduce the RF generated interference . You found like and old Wireless man ,like myself , a dying breed I am afraid . I had the same problem when working for BT when a digital telephone system kept on losing its programming in a factory due to heavy welding equipment . No amount of wire wound Ferrite core chokes worked neither did shielding the box holding the CPU /cards , in the end the box had to be moved. its a different matter if its only interference feedback into the mains circuit. Us “Old Foggies ” could teach the younger generation a thing or two but modern day social interaction is against that.


Old Fogie – I have been looking at the problem of radio interference by LED lighting for a few years now, and have now met people who have experienced problems, as well as reading about them on this and other websites. Problems seem to be more common with the 12V MR16/GU 5.3 lamps and could originate in the lamp or the driver, with the interconnecting wire effectively acting as an aerial for transmission of radio interference. Some have used ferrite products or screening (as Duncan mentions). It’s a good idea to move the radio or aerial, as you have suggested.

I suggest asking the retailer to replace the problem lamps or provide a refund. If enough people do this and give negative reviews then they might change their supplier.

Another approach would be to switch to mains voltage LEDs such as GU10s. These obviously don’t need drivers and I’ve seen fewer complaints about radio interference.

Mike Fulton says:
30 October 2017

I have recently (October 2017) installed a 13-watt Philips LED bulb in a bedside lamp, the bulb being at approximately 110 mm from the antenna of my FM radio. When the bulb is switched on, there is continuous interference, but not such as to completely blot-out reception of the station concerned (usually Radio 4).


I expect that if you move the radio away from the lamp, the interference will disappear. Light dimmers, microwave ovens and routers can also create problems at very close range and it will be more of a problem if you have a weak radio signal. It can be explained by the inverse square law. You might find that other LED bulbs work fine next to a radio but it’s best to keep them apart.

AndyT says:
6 January 2018

Same here but with one of those unbranded “classic” looking led bulbs in my bedside light.

Debra Saunders says:
18 November 2017

We just installed in the kitchen a 32 watt led ceiling light r-sunrise £16.49 from Amazon, now I have almost no reception in my fm rafio


I bought energy efficient led bulbs for my bedside lamps from Sainsbury’s. Since fittin them my dab radio only works when the bedside lamp is off. Do I have a right to return them?


There is no harm in trying, Jo. Before you do, it’s worth checking if moving the radio away helps – for example to the other side of the bed.

MKING says:
24 November 2017

We have A neighbour who has recently installed a rectangular floodlight in his back yard which is motion sensitive and has a dawn-to-dusk sensor. When the light is activated our FM reception is destroyed and a replaced with a very loud spitting/buzzing distortion for the two minutes that the light is active. The light is 8 METRES from the antenna which is an extended loop wire which gives a good stereo signal; the distortion is as bad when the radio is switched to mono.

This light has an internal power supply and probably a non-replaceable bulb unit. OFCOM (via the BBC) are being polled for action but it is not easy to get them out of their comfortable seats…


You have brought up a subject dear to my heart M.KIng — the “downfall ” of the GPO Radio Interference Group . I new a guy when I worked in BT who was in it. He went on at length that the government was “rationalising it -ie- as it has done to other government departments – removed its power , reduced its staff and turned it into another NGO that cannot do what the public want due to lack of resources . Your best bet is to change the direction of the loop wire and possibly replace it with a vertical aerial which extends outside the radiation area of the light . You could try putting a metal screen between the light and the aerial and earthing it . Normal RF transmissions form a pattern but you need to know the frequency of the signal to judge the pattern .If you use good quality screened tv/satellite cable and fix the vertical aerial higher up on your house that would help by being maybe outside the transmitted radiation field At the time private enterprise was complaining that the GPO service was “too good ” at detection and was causing them problems involving profit .


I would suggest having a word with your neighbour, who may be able to reject the floodlight as unsatisfactory. If they have paid to have it fitted, they might be less helpful. I once reported a radio interference problem caused by neighbours and it was dealt with promptly, but that must have been 35 years ago.

I would be very interested to know the outcome.


There is a legal remedy but I suggest you do what Wavechange has suggested in the first place. Your neighbours might not have been aware of the interference their floodlight has caused. You don’t have to put up with it or go to significant expense to curtail it so it might be helpful to have that knowledge up your sleeve when you talk to your neighbour.

Martin McIntosh says:
7 December 2017

Our DAB radio in the kitchen on the other side of the house cuts out completely as soon as we switch on the LED spotlights about 15 metres away on the landing or in the upstairs bathroom. The same thing happens with a different make of DAB radio in the bedroom. I replaced 50 watt 12v Hologen MR16 ceiling spotlights in our upstairs bathroom and landing with AuraLED AL-MR16PRO-7W bulbs, recommended by a local retailer. They were the only ones I could find that worked with the existing 12v transformers without flickering or strobing. Lumilife MR16 spots from LED Hut do not interfere with the radio signals but flicker all the time. Unfortunately I had been using the Auraled lights for some months before we bought the DAB radios and realised there was a problem.

richard hart says:
8 December 2017

In reply mainly to Mike Fulton, I believed I had exactly his problem. After several cheapo LED bulbs, I put a Phillips 13W LED replacement where I used to have a standard BC 100w, in my bedside lamp. The lamp is on a 4ft chest, and 4ft from my old Sharp radio that is usually tuned to R4FM. Immediate low volume pink noise over the audio as soon as the light is switched on. The previous LED bulbs were worse.

So I thought of moving the room around. After a hour or so of preparation I was ready to test, moving the radio further from the bulb. As soon as I started to move the radio, reception became clear. Reception remained clear when the radio was on the chest 1ft from the lamp. After some fiddling, I am satisfied that the interference is coming from the proximity of the radio and the lamp mains leads. They both plug into a block below my bedside table, and how the cables cross each other as they leave the block seems to be critical.


Richard if they both plug into the same block of mains sockets then its not the external wires as they are paralled inside the block so they have a common connection anyway so its not induction but RF radiation from the leads acting as an aerial . You proved that by changing the radio position . in the past decades most transistor radios received an RF signal via a ferrite rod with coil winding’s on it for different wavebands . The drawback with ferrite rods is that they are very directional and efficient unlike a long aerial wire and therefore can pick up more interference by their receiving signal loop of reception , but on the other hand they can null out a signal quickly , thats what you have done. This type of principle can be used for direction finding.


That’s unfortunate but interesting, Richard. It suggests that the interference is not being picked up by the radio aerial but via the mains cable and that the interference is also being transmitted from the lamp via its cable. Lamp dimmers can produce interference in the same way.

You might find it helps to extend the radio aerial. If you are game for more experiments you could try a different radio because they do vary in their ability to pick up interference. A battery-operated radio might not have a problem, but obviously would be expensive to operate.

Duncan – Richard says he is listening to Radio 4 FM and I guess he will have a telescopic aerial or simply a bit of wire on some bedside radios. I don’t think ferrite aerials are normally used for FM, but could be wrong. My old Hacker Hunter radio had great reception and sound quality but probably had poor screening because it picked up interference that caused no problem with cheaper radios. 🙁

David James says:
25 December 2017

Don’t know about dab, but these bulbs affect my hearing aids quite badly. This needs to be sorted and quickly.


If they effect your hearing aids David then you must have the latest wireless controlled ones for use remotely for communications with cell-net phones and other gadgets . Are yours automatic or can you switch to local reception cutting out the wireless section ? If not then use therm to their best advantage, you have in a practical sense an LED radiation detector , one step ahead of many others here . Why ? because ,unlike them you can buy ONE LED bulb of another make and try it out , or even ask the supplier , if you are buying then locally to plug one in to try it.Your reception(area of capture of signal ) will not be unidirectional so the reception area in RF terms will be wide .

Patrick Taylor says:
25 December 2017

A very interesting piece of information.


My DAB car radio suffers from this problem, I sometimes sit in the car to listen to football matches as it’s the only DAB radio I have. For evening matches I often trigger the LED floodlight on the drive, the radio is barely audible until the timer runs out and the flood light turns itself off, then the reception is crystal clear again (I think I need to buy a portable radio).


I have a cheap LED floodlight that I bought from Lidl to use as a worklight and that’s fine. Some manufacturers manage to comply with the regulations but others don’t seem to. I now know several people who have had problems but I have been lucky and have tested every bulb that has come into the house. It must be a real pain to put up a floodlight and find out that it wipes out radio reception.


Wavechange I have mentioned this before but so many complain about this I will repeat it. Maplin sell a bug tracer/tracker for £25 it covers 50Mhz- 3000Mhz Take it to shop – ask shop to plug in LED bulb-use tester – bingo !


Can you help me with a part number, Duncan? I’ve not had problems with DAB interference, just one bulb that affected an FM radio, though do know people who have had problems. I have tried to get hold of problem bulbs but these have just been disposed of and replaced by others. At least this demonstrates that there is an easy solution.


Sorry Wavechange !! I got through to Maplin,s “technical ” dept they dont do them any more nor Velleman kjits nor anything you build yourself its all ready made electronics — Maplin- RIP !


Ah well. Life moves on. The only Maplin kit I ever bought was a clock timer, back in the mid-70s. It turns my router off at night and on in the morning. Oops – we are off-topic.

Gary Williams says:
7 February 2018

I have a number of unbranded GU10 240V LED bulbs in our kitchen area. Nearly every time we switch them on our router resets, leaving us without an internet connection for 5 minutes or so while it goes through its reset sequence. I have not experienced this problem with any other LED bulb that we have. The bulbs causing the issued are located approximately 5m from the router.


Thats a serious RF problem when it cuts off your router its RF transmissions must be on a harmonic of the routers operating frequency Gary . As you need wi-fi it isnt a cure to screen your router . I would change the bulbs to a recognized brand . Every time your router resets various changes are made so its possible you could even lose speed for a day or two.


I agree with Duncan about switching bulbs, but I would also contact the seller and ask for a refund. If the manufacturer has not complied with the regulations on RF emission they might not have bothered about safety requirements either. There are many unbranded electrical products that are unsafe.

John Inge Nordfonn says:
21 February 2018

Led among other electronics make trouble for Ham operations as well. Interference so we cant use our radios. Plasma TV is the worst


QRM5 -John ?

Paul says:
30 March 2018

I’m having that problem now. I bought my bulbs at protuninglab, an online store. These are the fog lights and they are causing radio interference. I put some ferrite chokes on them today and the situation has improved a bit but still remains as a problem. I’m not sure what to do at this juncture.



Paul Ferrite chokes I know about fitted them to BT call-connect business system units on the input wiring in an engineering factory but the fault persisted coming from high frequency welding equipment locking up the CPU . Radios nowadays have directional aerials for high frequency gain , try moving the radios around . The chokes will probably be wide-band and not so efficient at the frequency involved. If its mostly induced in the ring main then fit a series HIGH QUALITY filter between the mains and the fog lamps.


Paul – I suggest that you contact the supplier and try to get a refund. It might be best to stick with whatever lamps the manufacturer recommends.

Rob Harrison says:
26 April 2018

In a recent European wide test of LED floodlights by two independent working groups, the results were extremely poor. The testing consisted of safety tests and meeting EU interference standards both by technical testing (meeting EU standards) and administratively.

Reference document here http://www.tukes.fi/Tiedostot/sahko_ja_hissit/JA2015-EMCLVD_Results_of_Campaign.pdf

Out of 87 safety tested only 9 met all safety standards and 76% were considered dangerous , posing a shock risk. For EMC testing only 47% met current standards up to 30MHZ and 55% were OK from 30-300MHz. For combined safety and emc/admin’ testing only 5 lights passed both tests.

This is a damning indictment of the way consumerism has degraded the quality of products in general and of government(s) not properly funding the relevant standards authorities to keep poor product from the market.

Solar panel RFI, plasma TV, and PLT(data over the mains) are to other major contributors to EMC pollution. Ofcom do not want to know and have changed their interpretation of what is considered harmful so as to allow their very limited resources to deal with only “danger to life” situations. They take reports of local interference, but very rarely act. Last April new legislation was enacted to specifically address these problems. However, Ofcom don’t seem to want to use these powers.

This is just scratching the surface of the problem of non-compliant product swamping the marketplace in all areas, not just electronics.

Angry Ham,



Rob-As a Radio Amateur (HAM ) you must know the history of the GPO Interference Group which was severely downgraded by HMG allowing CD radio to boom and even ( illegally ) overlap the 27Meg bandwidth range allowed including RF amplifiers over-watting their output etc. This was the start of the downfall of real action being taken by the public to combat this and is part of “Open Britain ” as in third world open . I worked beside a GPO guy who worked in the Interference Group before BT went private separating itself from the GPO , meaning I couldn’t go into GPO canteens and started getting parking tickets . He told me all this was going to happen and he was right . Its part of US globalization now and I dont see any real action being taken unless there is a change of government as the government= big business .

Denis says:
3 May 2018

I changed out five 12V 50W MR16 halogen downlighters for 12V 5W MR16 LED downlighters. Interference swamped my and my neighbour’s FM and DAB. The 12V individual power supply units were rated for a minimum load of 20W so they didn’t match the 5W LEDs. I changed the lot out for 240V GU10 LEDs, a mix of Integral and Aurora. The interference ceased, except for a whisper when a radio was held up against the bulb.
It does not appear to be common knowledge that you should not replace 12V halogens directly with 12V LEDs. Not only does it cause interference but carries a risk due to the power supply driving an incorrect load. Perhaps LED manufacturers should have a warning on the packet.


The MR16 halogen downlighters in my bathrooms were on individual power supplies and I wondered if these drivers would work satisfactorily with MR16 – LED replacements, expecting to have to remove the drivers and rewire the fixtures to accept GU10 LEDs, as you have done. I tried one and the only interference I could detect was when an FM radio tuned to a weak station was close to the lamp, and there was no DAB interference. I then replaced all the halogen lamps with MR16-LEDs and they are fine. I was lucky but agree that manufacturers should put a warning on the packet.

Dimmers installed for incandescent lighting might not work properly with LED lamps and might cause damage to them. Why isn’t this mentioned on the packet?


This sort of thing crops up again and again in convos in relation to LEDs , I have posted the answer time and time again , obviously its going in one ear and out the other . Of course they dont work off the same power supply for one simple reason LED,s require a stabilized CURRENT DRIVEN power supply NOT a VOLTAGE DRIVEN one . I hope this sinks in but I doubt it.


MR16 LEDs operate on a nominal voltage of 12V. Specifications often don’t give a range of acceptable voltages or even state AC or DC, which is not very helpful. I’ve fitted 12V LEDs in off-grid applications where the lamps are powered by 12V lead-acid batteries. Here the voltage can reach 14.5V when the batteries are being charged. The better 12V LEDs sold for this sort of use will run on 10-30V DC and are protected from spikes produced by the alternator in the generator. I doubt that the ones sold for household use will accept this voltage range but if it was critical I suspect the specifications would make this clear. The drivers I have seen were AC output and will work on DC, so presumable there is a bridge rectifier on the input.

I am well aware that an individual LED must operate at a controlled current but the SMPS that drives one or more LEDs ensures that this happens despite variations in the input voltage.


duncan, that is correct. The current needs to be controlled. However, power supplies are of two types, constant voltage and constant current depending upon whether the LED has current control on board. As I understand it.


Oops, my post should read: ‘The drivers I have seen were AC output but the LED lamps will also work on DC, so presumable there is a bridge rectifier on the input.’

Malcolm – MR16 lamps – which is what we are discussing here – all use drivers that provide approximately 12V. Yes there are other types of LED lamps that use constant current drivers.


Malcolm I know about both types as I have built many sophisticated constant voltage power supplies for for top end audio designs and test equipment over many decades starting with the OC high power range of germanium BJT then silicon ending up with high power Mosfets . As regards constant current I have a large collection of small LED,s to test the working CURRENT I have built a variable voltage supply which I slowly increase the voltage of watching the brightness increase of the LED this gives me an indication on a milliamp-meter of the working CURRENT of the LED , I can also do this with a professional stabilized variable voltage/amp meter with two digital meters which can be either voltage indicating or current indicating – two channel . Voltage and current stabilization goes back to the twenties there are many valve versions of both and I have some which plug in like valves for RF reception do some were gas filled .


I replaced six 120 Watt Par38 lamps in the kitchen of my recently acquired house. The first attempt was a set of fluorescent based PAR38 format lamps (remember I have big holes in my ceiling and that limits the choice) but they took too long to come up to full power. Next I tried a set of LED based PAR38s from TLC (Southern) Ltd and they were quite good except for their short life before one or more lost elements. Some cheap Chinese equivalents came next and they were good but too cold in colour temperature and were consigned to my garage. None of these threw up any serious EMI problems. Eventually I bought a set of LED round panels that fitted into the ceiling holes perfectly. They are edge illuminated panels with 12Vdc LED lamps that give an even disc of light and each consume (claimed) 12W. That is when the trouble started with FM stereo reception picking up an all-encompassing white noise interference. I tried complaining to the supplier as they fittings carry a CE mark and he told the Chinese makers that they could not have gained a CE logo while pumping out so much EMI. They went through the motions of sending me a new set FOC but these were just as bad. To be pragmatic, I simply switch my radio to mono and carry on and unless BBC Radio 4 is down on power the reduced hiss without the stereo decoder in operation is acceptable for the excellent quality of light I have at a mere 72 Watts versus the 720 Watts of the old incandescent PAR38s.
I am pretty sure it is the switch mode power supply causing the EMI but I haven’t done any trials with known ‘silent’ PSUs.


Motco-From what I know on the history of this its no “great shock ” to hear your CE labelled light has RF interference its a “known ability ” of some Chinese companies to onerously label LED lights and other electrical equipment “CE ” .

Now this is a big issue with me as some people seem to think “its not possible ” even though I posted 2 years ago on this and I have the Chinese government export rules which are pretty draconian in places including non-re-entry of their export goods .

WHY – because the Chinese government wont let you send back OR legally reference the MANUFACTURER based in China -FAULTY goods .

So knowing some peoples “disbelief ” I post the URL from a company dealing with IMPORTERS and the law relating to China ,
please scroll down to the relevant paragraph –
Which Party is Responsible to Ensure Compliance with All Applicable EN Directives?
When products are manufactured overseas (e.g. in China), the importer is responsible to ensure compliance with the applicable EN Directive. This often comes as a surprise to European importers, as most EU authorities, and their websites, tend to refer to the “manufacturer” as the party responsible to ensure CE compliance.
However, when items are manufactured overseas, the importer is considered being the manufacturer. Thus, the responsibility to ensure ‘CE compliance’ cannot be shifted to a Chinese manufacturer.


Please note this is in addition to the Chinese governments strict rules on this subject.

RF detectors can be bought but for Wavechanges information I post a US top end one
way out of the range of the public’s version as it is technical -shows graphs and is made by Tektronix
a highly respectable company of whose products I have and can guarantee their quality
only available as an import


As I said cheap ones are available in the UK.


One of the units failed this week and I tested it with a known good power unit. The illuminator (for the want of a better term) is okay so the SWPS is responsible. Opening it up reveals an 8 pin DIL IC, a few surface mount components, a small transformer or inductor, and two Al. caps. In my recent experience cheap Chinese Al. caps. have a limited life so they would be my first port of call to replace. I was Technical and Marketing Director for a manufacturer of security equipment for ten years and never experienced an aluminium capacitor failure except when cross-polarised. As you will know, there’s no doubt about that sort of failure! The light source is a good product but it is spoiled by a poor quality power supply with no attention to EMI suppression.
Here’s my ad hoc EMI test https://www.youtube.com/watch?v=31XuC1hds2w


Its good to “talk ” to someone of your tech knowledge Motco I am impressed .
Your absolutely right those AL caps aren’t what you would call “top end ” in a lot of smps,s having to deal with a lot of HF , I used to post on WW/EW and one Prof. Engineer was a capacitor specialist since the 60,s and he designed specialised testing equipment , too much work for me so I didn’t build it but it was in relation to top end audio where even a minute amount of dist. was audible.

The problem with China is the vast amount of factories doing the same component making although this plays right into the hands of “money saving ” importers .


You flatter me Duncan, I am not really that knowledgeable. My training was in polymer technology and engineering many years ago and what knowledge I have of matters electrical/electronic have been acquired as an enthusiastic amateur over several decades. It started with being impecunious but keen on having decent music reproduction equipment. Rather than buy one of the frankly poor new-fangled cassette decks, I bought a Heathkit open reel tape recorder kit and building that and ironing out the inevitable snags piqued my interest in electronics. Moving on a couple of decades I was left standing when all others had sat down when the small company I worked for bought the rights to a novel design of Doppler microwave device. That was a steep learning curve I can assure you! Because I was the only senior member of staff with any electronics knowledge at all it fell to me to milk the boffin who designed it of all the information I could. A modicum of intelligence and the motivation to survive in the job spurred me on to do my homework avidly! Ironically the inventor of this device was also unqualified having learned all he knew by experiment and being a radar tech in the RAF. Life deals a hand and it behoves us to play the cards to the best of our abilities and not to be narrow minded and inflexible. I shall now release the thread from this hijack! Oh, and yes you’re right about Chinese manufacturers. I spent a few days with a Taiwanese manufacturer who was making one of the early PIR flood light controls for us in the 1980s. I was horrified to see the total lack of safety concerns in the disparate little sub-contractors’ units. Mothers soldering up boards with their babies asleep under the bench for example. It’s better now, I’m sure and far more automated, but the working conditions will not be too different.


Motto-Thanks for the honest and straightforward answer to my post , I too do not have a university degree education but I am cursed with having a modicum of intelligence which I have found is not always welcome in society.

Yes I remember Heathkit well I built/bought some of their test gear in the early days you now have to deal with America if you want electronic parts without fuss for those UK builders still left in this country as engineering is played down in this modern society in favour of “social graces ” .
To me this stifles innovation as you rightly say the inventor of the Doppler unit was unqualified as it shows you you don’t need a string of letters after your name just a bit of intelligence and yes I too got help from a ex.RAF radar tech. who left me all his books and hardware before he died of cancer .

Nice talking to you Motco –don’t be a stranger here.

joan reekie says:
19 December 2018

can led street lights interfere with mobile phone signals


Theoretically yes Joan depending on the quality of the power supplies to them and the fact that back EMF (voltage ) containing RF products at high frequency use the supply cables coming up the pillars as aerials to transmit the signals .
Harmonics can be strong enough as well , depends on the purchasing power of your local council and quality .
In a nut shell —yes its possible .


The distance is going to be a major factor and anyone that if a streetlamp is very close to the house, interference is most likely. Interference can also be carried in the mains electricity supply to a home, particularly if the streetlight is on the same phase (there are three) as the house. The easiest way to find out if there might be a problem is to see if there is a decrease in signal strength when nearby lights come on, but bear in mind that signal strength can vary under different weather conditions.

If there is evidence of a problem then the local council should investigate, but it would be best to find out if others are suffering the same problem when the lights come on.


If it’s dark enough for the street lights to come on you probably need to stand underneath one to see what you’re doing, although the modern LED ones do seem to give a clearer and better light spread than the old sodium ones. Our cul-de-sac with about 30 houses has just three street lights and it seems to be well enough illuminated until midnight when they go to sleep for a few hours.

We seem to have discussed the possible effects of the power supply and circuitry of the street lighting rather than any interference effect from the LED lamp in the lantern itself – which is what I assumed Joan was asking about. I have no knowledge of the latter but the main advantage of using LED’s is the much lower power consumption so there will be a much lower current in the power supply running up the column than with previous types of street lighting. I don’t know whether the control gear at the base of a street lighting column generates any stray currents or electro-magnetic interference but again I would think a lower power demand through using LED lamps would be likely to have a moderating effect.

Kerbside power stanchions for electric vehicle charging might introduce a new source of interference and the electrical current could be considerable depending on how many feeds are provided.


A lot depends on the design of LED streetlights. When LED lights were fitted in our street a year or two ago the spread of light was very poor and I could no longer see to find the right key for the door, but it is much brighter below the lamps. Elsewhere the move to LED streetlights seems to have been an improvement.

Hopefully street lighting will be made to better standards than some of dubious products that are sold to the public but electronic drivers used for LED lighting certainly has potential to cause interference.


“Why have I lost DAB radio stations?” is the query in January’s print edition p39 (sorry can’t find it online).
WiFi is suggested as likely – but the author doesn’t address all the other RFI causes esp. from LED lights that are discussed here. And he speculates about new factors that are not reported by the OP e.g. that broadcast coverage has changed, or the building has become steel-framed!
I now feel more expert in all this than the Which “tech expert” – so thank you all.


With regard to LED street lamps, unless they work on a fundamentally different principle from ‘normal’ LEDs, the lamps themselves are likely to be running on a DC supply derived from a power supply located within the stanchion and supplied, in its turn, from the 230Vac public supply. It is the means of converting 230 volts of alternating current into x volts of direct current that could well be implicated in any electromagnetic interference (EMI) problems. Domestic LEDs use switched mode supplies and there is often a poorly designed (i.e.cheap) level of electrical ‘noise’ suppression. An old fashioned transformer and voltage regulator type is only likely to produce low frequency emissions (50Hz) from the transformer and not very strong ones at that. However these power supplies are expensive, bulky, and relatively inefficient compared with switched mode supplies and are, therefore, not the first choice. My knowledge of the workings of switched mode supplies is sketchy but I built one for operating my car headlights in a dim-dip mode (1/10 normal power) as legally required on new vehicles for a short period in the 1980s by construction and use laws until the EU over-rode them. This was a square wave oscillator with a suitable mark-space ratio to switch a power transistor on and off rapidly make the filament lamp appear to be smoothly dimmed but to dissipate as little energy as heat as possible. Regrettably its use rendered AM radio unusable due to raucous noise on the car’s electrical system. I gave up at this point! I believe that modern switched mode supplies use fundamentally this rapid on/off running and that the noise generated has to be suppressed in order to meet CE certification. Sadly CE logo stamps are ten-a-penny in the Orient! Take an AM medium or long wave portable radio tuned away from any stations or tuned to a distant one, and move towards the illuminated street lamp and see whether the interference can be heard to increase with your approach. If so, that points a finger at the lamp post.


Yes Motco a square wave signal is the most efficient digitally but the worst as far as RF generated harmonics , they just go on and on .
From a 50Hz peak -150Hz-250Hz-350Hz -450Hz ad infinitum and if the conversion components change value its a whole spectrum of HF oscillations , as the harmonic number increases the signal output decreases but that is relative to the original power output .
It can be seen clearly on a Spectrum Analyser or the use of Electronic Engineering -digitally produced SPICE display .
Thats why I never use a graphic analyser to vary the tone as it introduces distortion only hi-fi amps I build with 0.001 THD and very good transient response using as small as possible comp value ( compensation capacitor ) to remove instability.
As the public have found out it depends on the values of the passive components as to the frequency range as I was quoting ideal circumstances which would never be the case in cheap components the capacitors the first to go .

I should accept that local councils will have a Technical Engineer at their disposal but nowadays that is a “bad word ” and the money would be put to “other causes ” of a social nature .
You can buy RF wideband signal detectors quite cheaply , you dont need accuracy of frequency only signal strength indications .

Unfortunately with all this “spy business ” the publicity has proved popular with the Spy Bug Industry and they have relabeled them and are selling them for £2000 .
those interested and can solder components together and read simple electronic diagrams I can direct them to an “old school ” electronic circuit website where they can be built for (approx ) £20/£30 .
Most of the cheap ones are in the USA where Homebase (USA) -$80 and who,s website thinks I live in Cumberland.

NickM says:
2 January 2019

We had trouble with the reception from our kitchen DAB radio in the summer; it was around 10 years old and we thought it was the radio and replaced it; about 3 days later we noticed that the reception from the new one developed exactly the same problem when the kitchen lights were turned on. Replacing the LED lights (x9) with halogen spots solved the problem but now I find that halogen lights are being phased out! Are there any LED brands that do not do this? In the meantime have stockpiled some halogen bulbs……


Nick Philips do a range of no interference LED bulbs .
Technical achievements move on fast nowadays you can buy directly fed (AC mains ) LED bulbs with a simple diode circuit -no SMPS or the latest AC LED bulbs ,there is also an “element ” type .
You can even build your own -WARNING do not attempt this if you are not suitably qualified or trained !
Below is a simple AC fed circuit that I guarantee does not send out HF RF noise for Wavechange –
https://www.electronicshub.org/mains-operated-led-light-circuit/ also-


Thanks Duncan. Some devices such as Christmas lights have simple circuits including a capacitor, bridge rectifier and a couple of resistors, as shown in one of your linked articles, and there is no chance of radio interference. I believe that LED lighting generally uses high frequency drivers that pulse-feed the LEDs to achieve higher efficiency, albeit with the risk of radio interference unless this is suppressed. I’ve bought at least six brands of LED lamps and only one produced interference and even then only when the lamp was close to the radio. Maybe I was lucky but I did avoid buying cheap lamps online.

I suggest that Nick experiments with different LEDs bought locally and takes them back for a refund if there is a problem.