Severe MW interference solved

[newlite4]

Well, it took me some time, but I've done it. The culprit is an LED bulb in the hall table lamp in the basement flat. Being empty in between holiday guests, I nipped down with my keys and turned it off, the result was perfect MW reception. I will now contact the owner to get the go ahead to swap it out for a CFL instead, it can't be any worse!
Neil

[Hybrid tellies]

Nice job Neil. Tracing interference is often a nightmare. But be warned that some of those CFL bulbs were also bad RFI offenders.

I am still trying to find out which type and make of LED bulbs are bad sources of interference and which ones don't radiate any interference.
I think the those that are dimmable and don't use a nasty noisy driver circuit but use a linear PSU/driver unit such as a capacitive dropper are the best ones to use.
Trouble is you have to buy a LED bulb first to trial it out as there is no information out there on the amounts of RFI these LED bulbs throw out.

[newlite4]

Just an update, nipped downstairs armed with a CFL and found that when the LED bulb is removed from the table lamp, the interference is still there. It is being generated by a row of four triple LED sunken ceiling lights behind me which I had not noticed at first. I have left the hall lights off for now, it looks like the interference is going to hang around for a bit yet, but at least I know what it is.
Neil

[paulsherwin]

LED GLS bulbs have a bad reputation for noise, but most are actually OK. It's exactly the same with CFLs.

Unfortunately there's no way of spotting the noisy ones in the shop. Price is no guide - the Poundland ones have been fine in my experience. I wonder if the noisy ones are simply faulty.

[Radio Wrangler]

I've started putting large ferrite beads on the cabling to lights on the assumption that they'll have to go LED at some time. CFL seem to be going the way of the dodo.

Snap on split ferrites are easy on the pendant drops, but whole rings are a lot cheaper where you're taking things apart. I'm building into the distribution system the EMC filtering that should have been in the bulbs.

David

[newlite4]

Yes, it threw me a bit because the table lamp is hard wired in to the hall lighting circuit on the same switch so removing the table lamp led revealed the real cause behind me. Still, I think I've got problems, check this out from OFCOM :

https://www.ofcom.org.uk/about-ofcom...rference-issue

Neil

[AdrianH]

Unfortunately it will probably take a few high profile cases like that before OFCOM and Trading Standards do something about noise pollution. And when they do it would still be several years for such lightbulbs to fail and be taken out of service.

Adrian

[Julesomega]

In thread LED Lightbulb Teardown I described how the Top-Max bulbs can be cut open and the BP5131D tested, but in every case I found that the problem was the connector betwen the supply and regulator board becoming intermittent as the silicone adhesive expands with use and can be cured by removing the adhesive and soldering the connector in place

The way to choose these Top-Max bulbs is by weight! They weigh a lot less than the SMPS types

[clockman]

The MW interference in my house is at a very high level in places. So I use a little MW portable as a detector to find the the lowest level areas as it seems to move to different areas. Thanks for the info re LED lamps.

Ofcom can be good for amateur radio frequencies, I have had them round a few times for PLT interference (and they went away after) I have no alternative as to what frequency I use.

I did ask and the (wonderful and knowledgeable) gentleman from OFCOM who said, "if it's MW/LW we don't bother much just advise that clean reception is available on other services, however if a specific frequency is specified in the complaint and the content isn't on other "platforms" we may take notice".

Worth a go at OFCOM, you never know! Just make sure your house is completely innocent.

[Jon_G4MDC]

That Ofcom story shows an incandescent bulb (can see the filament) which was supposed to have caused significant noise in air band. 119.1MHz is shown.

I'd like to know the mechanism for that. Arcing at the contacts on the base?

[Nymrod121]

I did some ad hoc testing back in 2016, albeit at DAB Band III ...

https://www.vintage-radio.net/forum/...57&postcount=9

https://www.vintage-radio.net/forum/...5&postcount=10

At the risk of being labelled a 'vintage radio Philistine', I've never really bothered with M.F. radio reception because of this type of issue ...
Best regards
Guy

[Techman]

I'm wondering about that OFCOM report. It says, and I quote "Specifically, the cause was four ‘vintage’ lightbulbs that the homeowner had recently bought online", but they look modern and just 'vintage' looking. They look like filament bulbs, but are they? If they were, then perhaps they were run via a dimmer and it was this that was more likely to be causing the interference rather than the bulbs/lamps themselves. The lack of proper explanation makes me wonder about the technical level of the person who wrote it up.

Regarding OFCOM coming out to look into PLT interference mentioned in post #10, that's a new one on me. Not that I've ever tried to call them myself, but my understanding is that they're far too short staffed to be bothered with complaints from private individuals, as they get hundreds that they'd never be able to deal with these days, so wondering how recent this was?

[Aub]

Are these the same/similar? These are in our outer hall and are dimmable LED .

Cheers

Aub

[MurphyNut]

Well done, nice when you can locate the problem and able to rectify it
I had an interesting one recently, I bought some LED "flat panel" lights which are remarkably good giving bright evenly sped light but taking up hardly any space. I knew they would interfere with MW / LW, and they certainly did. But even with them switched off there was still unwanted noise, I finally found out it was coming from the plug, it had a built in transformer to drop the voltage and was radiating interference.

so wondering how recent this was?

The last time was five or six years ago, the OFCOM chap that came round said I had to specify a frequency (in a "public" band). Over a cuppa we had a look at the waterfall display and he said, "That's the biggest that qualifies, lets find it". When found I was asked to go home (privacy etc.), not long after the noise had gone. Apparently the interferer was ex Navy radio and was horrified by his PLT doing this and removed it there and then.

Another cuppa and more biscuits where supplied. Probably the last of the proper radio interference bods left, retired now I suppose.

[Techman]

Originally Posted by merlinmaxwell

The last time was five or six years ago,

Another cuppa and more biscuits where supplied. Probably the last of the proper radio interference bods left, retired now I suppose.

I thought it must have been a while ago. I've never met anyone whose had any success in getting that type of interference sorted out in recent times. I think your hospitality went a long way in helping to get the end result and also the understanding individual who was unwittingly causing it. You did very well, I doubt you'd be so lucky today.

[AdrianH]

Was it not 18 months for the interference in that village?

Adrian

Here https://www.ofcom.org.uk/complaints/...-amateur-radio is interesting reading. I used it for my case.

[kalee20]

Originally Posted by Jon_G4MDC

That Ofcom story shows an incandescent bulb (can see the filament) which was supposed to have caused significant noise in air band. 119.1MHz is shown.

I'd like to know the mechanism for that. Arcing at the contacts on the base?

I have heard Barkhausen oscillation postulated as a source of emissions from vacuum incandescent lamps.