Humming Light Fixture.

[Macflame]

I have a kitchen/Diner that has two light fittings at opposite ends of the room. There are three switches. A double switch at one end, nearest the front door, to switch on both lights and a single one at the far end to switch on the light nearest it.

The latter light gives off radio frequency interference, which is heard over the baby monitor. This is the light controlled by switches at both ends of the kitchen/diner. No other light fixture does this.

The rose and the switch ahve been changed but makes no difference.Can anyone explain what is going on?

 

[breezer]

You have answered your own question

The latter light gives off radio frequency interference,

 

[Macflame]

I know that it is RFI from the lgiht fixing that is causing the hum on the baby listener. What I meant was, why is it that a light fixture should send out radio waves that can be picked up on public channels i.e. the baby listener.
The lights before and after the RF emitting light are o.k.

 

[breezer]

its just the fact that your baby monitor picks it up, nothing to with "public frequncy"
if you did not have the baby monitor it would still emit rfi but you would not know

 

[Macflame]

Hi Breezer. What I meant by 'public' frequency is that the light must be emitting RF at 2.4Ghz or there abouts. This is the unlicensed frequency used by baby monitors, video senders and PC wireless networking devices to name but a few.

My question is really directed as to why one of my lights is sending out RFI and all the rest are not. Could it be that there is some rapid sparking occurring that would cause RFI, as in an un-surpressed car ignition system.
Could the wiring be acting like an electro magnet and sending out radio waves.

If all the lights gave off RFI in the 2.4Ghz range, then I could accept that. But why only the one light?

 

[breezer]

some days you wake up with a headache.

are you saying all light fittings are identical?

oh and rfi by its nature has no dedicated frequency, that is why it is rfi

 

[reggie perrin]

That just comes across as a really snotty reply old chum...

 

[securespark]

From a previous post by Reggie:

If you have the knowledge to help people then impart that knowledge with grace - not arrogance.

Have you the knowledge?

If so, why don't you help?

 

[breezer]

reggie perrin

its not meant as a snotty reply.

But since the op mentioned rfi, I assumed the poster knows what rfi is.
Rfi by its own nature is not at a specific frequency, it covers a whole spectrum, the fact that his babymonitor can only pick up a specific frequency does not mean that is the frequency the rfi is on.

I also asked are all the light fittings the same, and it would be a differnt answer if they answer is yes, but since they have not replied, and you have butted in, what else can i say


securespark, nice one

 

[Macflame]

Thanks reggie perrin and securespark. I was beginning to think I that I had one too many wine gums!
I thought it was a straight forward enough question i.e. why is one of my light fittings interfering with my baby monitor! All the downstairs fittings are the same and were fitted when we had a new kitchen installed.
I must lay down now. I've got a headache!

 

[RF Lighting]

I seem to remember seeing a wiring diagram (possibly at college) for 2 way switching, which when wired like that was less likely to cause problems with rfi.

I think it was recommended for use in places which were fitted with hearing aid induction loops and the like.

 

[Macflame]

Thanks RF Lightning!
I now have a starting point to track down the problem.

 

[Adam_151]

Fwiw, my thinking is that if you separate 'flow' and 'return' at any point along their length you'll be creating a system which to a certain extent puts out a 50hz field.

If the wireing is in DI singles (or singles in conduit) it is quite easy to create such a situation (though I expect that if the conduit was metal then the effects would be a lot less than if it were plastic, though you do have the other issue in it trying to induce a current in the conduit with the metal!)

Things like broken conductors on rfc can cause similar issues, as the current sharing on the conductor that is broken is lost, while remaining on the unbroken conductor