RF noise in 12 volt fluros.

Submitted: Monday, Sep 29, 2003 at 21:49
ThreadID: 7505 Views:2415 Replies:4 FollowUps:5
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I tried to reply to a previous post - but keep getting the flick ...


Same here Ken.

We tried single 8W then double 8W - both made heaps of noise through the car radio - especially when in a distant location, where the radio signal is weak.

I was convinced that the interference was coming back through the 12V wiring so we bought a stand alone Arlec 20W rechargeable - but it does the same - noise!!! It is a much better light than the smaller units though.

Then I came across some Nelson 12V/12W compact fluro bulbs. These physically look like a normal 240V high efficiency compact fluro - and are available with the normal bayonet or edison screw fittings.

WOW - much better light than the Arlec 20W fluro and NO NOISE!

I bought mine from Bunnings and used the bayonet type because a HPM switched batton socket is available for bayonets but not Edison Screw types. This makes it easy to make up a switched lead.

Have a look at:
Then look in the 'Garden Lights' section and scroll down to the 'ELV' (Extra Low Voltage) section - there are two colour temperatures available - Natural or Warm White - both available in either bayonet base or Edison Screw base. You will note that they have built in 'Radio Interference Suppression'.
Print off the page and take it to your local lighting specialist distributor.

Current draw is 1 amp and they run cool.

We now have three of them!

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Reply By: Member - Ken - Monday, Sep 29, 2003 at 23:39

Monday, Sep 29, 2003 at 23:39

It's good to see you have joined the 'coalition of the willing' who I hope will be able to obliterate the weapon of 'mass RF interferance'.

I will definitely check out those Nelson fluros, as there a Bunnings 'Barn' about a kilometer from me. Sounds an interesting possibility/alternative.

Taking the hints and advice in the replies to my initial post, I went to JAYCAR today and had a chat to the 'expert' there. Never had a clue about the RF noise factor from the said fluro's.

However he convinced me to buy a 'new generation fluro' - 11W with an ELV type tube in it equiv. to a 60W incandessant. He was of the opinion that this new generation sucker would have that RF thingo eliminated.

So I bought it on the condition that I could return it if it produced that RF thingo. ($40.00)

I then queried him about RF chokes. Damn! if he didn't know his stuff on these items. Took me straight to the rack that contained them and picked off a packet containing 4 cylinder type ones that could be opened, placed around the offending cable/s, and clipped shut. Had about a 8mm centre core (Hole).

He assured me that these were the ones for AM radio interferance. So I bought a packet of 4 ($11.00.)

I get home with enough light left to test this new wonder light, and grabbed the 12V power pack and sat it on the bonnet.

Turned on the radio and picked a prick AM station.

Connected up the 'new generation fluro' and placed it within 25mm of the radio aerial and fired up the fluro.

Guess what! That AM radio screeched and warbled its guts out.

Sooooooooooooo! not to be deterred I whipped one of the RF chokes around the power cables.

Absolutely exactly the same. So I added the whole 4 RF chokes to both the cables with no change in the noise emanating from that AM radio. However by sliding the chokes up and down the cable I managed to play a noise tune of sorts.

Then I remembered some gentleman suggesting wrapping the cables around and through the RF choke.

Weeeeeeeeeeeeeeell! I used one choke and wrapped it once. All I can say is thank you mate as that reduced the noise by around 90%, and thats with the offending apparatus right on the aerial.

By this time it was dark, so tomorrow when I get home I'll give it two wraps of the choke and a third if I can fit the cables and see how that goes.

I will let you all know.


Ken Robinson

AnswerID: 32361

Follow Up By: David N. - Tuesday, Sep 30, 2003 at 09:15

Tuesday, Sep 30, 2003 at 09:15
Thanks Ken
Keep us informed, veeryy inteeresstting!
I always assumed the cheap flouros were too difficult to fix this problem... Will you try it on your cheapest (noisiest) flouro too?
FollowupID: 23131

Follow Up By: Member - Ken - Tuesday, Sep 30, 2003 at 21:16

Tuesday, Sep 30, 2003 at 21:16
David & Tuco

Yes, I am going to experiment on the 'old' dud el-cheapo's.

Further to this I went back to JAYCAR today and resumed dialogue with yesterdays salesman.

Now this is interesting. Yesterday he sold me RF chokes which I now know to be the 'hinged' variety with a 8mm bore. ($11.00) for 4.

Today I find that they have the solid type in 6mm & 10mm cores. 6 to a packet for about $5.00 each.

So I bought a packet of each because their overall diameter is significantly smaller than the 'hinged' variety.

This is important for me when I have to put the wiring plus the chokes back into the body behind the fluro batton fitting.

That will be my next hurdle, however a bit of lateral thinking will get around it as long as the noise is gone.

Due to current work committments, all I can say is that I will get to it before going to bed this coming Sunday, and will post the results.

If you want to contact me direct, you can on Ken_3149@yahoo.com.

By the way,I am going to the Melb 4WD show at Sandown this weekend, so I'll keep my eye out for whatever.


Ken Robinson

FollowupID: 23182

Follow Up By: Tuco69 - Tuesday, Sep 30, 2003 at 21:58

Tuesday, Sep 30, 2003 at 21:58
Ken - I think that when you try the Nelson ELV's that you will be impressed.

As well as the AM broadcast band radio, we have a HF Barrett 550R that we use regularly and sometimes just listen to the 'galah' sessions on the RFDS frequencies. The screeching and wobbling noises that the other lights were introducing to the HF set was enough to make us either listen in the dark or turn the HF off!

Best of luck.

FollowupID: 23185

Reply By: joc45 - Wednesday, Oct 01, 2003 at 08:38

Wednesday, Oct 01, 2003 at 08:38
Yeh, I got pi$$ed off with the cheap 10w flouros which created havoc on radios, and I eventually bought an 11w VersaLight (not cheap at about $90), but it's pretty quiet - not perfect, but not bad. And in a rugged case, and Aussie-made.
It is possible to quieten the cheapies with filters and mesh screening, but as said earlier, it's easier to track down a light which is intrinsicly quiet.
As an aside, it was frustrating that friends always wanted to have skeds on the HF just at mealtime in the evening (meal got cold) and lights were needed (interference). I put together a light for these occasions using a domestic 12v 20w halogen with the dichroic reflector. Not as efficient, but real quiet! When the sked was over, we reverted to the flouro.
AnswerID: 32458

Reply By: Hoffy - Wednesday, Oct 01, 2003 at 08:42

Wednesday, Oct 01, 2003 at 08:42
Hi All.
I have been looking recently for decent 12 volt flouro lights for our new caravan. In our previous van I used a Versalite unit which is "equivalent" to a 75 watt lamp. This worked well drawing around 1 amp and giving excellent light output. As well it created no RF interference. This was a good thing as being an amateur radio operator and wishing to contact family at home a no interference lamp was essential. We have now purchased a new van and SWMBO has told me I cannot string the Versalite up on the ceining.

Following the clue on this thread I went to Bunnies yesterday afternoon an picked up a Nelson "natural" 12 v flouro "equivalent" to a 60 watt lamp. The light output is not quite as good as as the Versalite but not too far behind. Current draw is .75 amp. Radio interference is zero. It appears, that in my case, I can remove, from the existing light fittings, the very inefficient "tail light bulbs" they use for 12 volt lighting and with a bit of surgery fit the Nelson lamps. For a lamp under $30 I think this will solve a lot of problems for many people.

I have, over the years, had some cheap 12 volt flouros. They draw the similair current to the more efficient units, create bags of RF interference and give bugger all light out put compared to the better units. I would not even try to supress any of these cheap ones. You would need to build a new properly designed inverter.

Thanks to Tuco for the lead

Happy seeing and listening without any interference.

AnswerID: 32460

Follow Up By: Member - Ken - Wednesday, Oct 01, 2003 at 21:39

Wednesday, Oct 01, 2003 at 21:39
KeithThanks for the input.

Read my last response to get an update on things.


Ken Robinson
FollowupID: 23255

Reply By: chrisfrd - Wednesday, Oct 01, 2003 at 16:23

Wednesday, Oct 01, 2003 at 16:23
Hi there guys.

The reason that these lamps make so much noise is that they are powered by a balast that is pulsed by a thyristor. The switching noise spreads through much of the radio spectrum and has a high amplitude.

All of the lights of this variety do this as their balasts are not shielded in any way at all. This is an issue as the lamp would not pass the C-Tick regulations!

These AM waves really screw around with the receivers gain controllers and you will not be able to do much to get rid of it. FM radios should survive this, if the stations are strong, but if it isn't - Look out!

If you are a handy-person, you can fix this permenently! All you have to do is make an metalic shield for the balast electronics. I've used a metalised platisc for the shield. You could use heavy aluminium foil (such as a glad baking tray) to do the same thing. I recommend using a ferrous based material, however.

You will need to insulate the whole balast electronics board, leaving holes for only the cable and the lamp fitting. Connect an earth wire to the shield, then to the negative supply wire (black) so that any stray pulses are forwarded to the negative supply of the battery.

I also earth the vehicle, when stationary, with a simple earth peg, connected to the chassis by a heavy wire. This completes the circuit and shunts most of the noise to earth.

Have fun!

AnswerID: 32502

Follow Up By: Member - Ken - Wednesday, Oct 01, 2003 at 21:36

Wednesday, Oct 01, 2003 at 21:36
Thanks for the feedback and advice mate.

I don't want to have to get rid of the current fluro's (the screech bastards) because their overall profile suits my need s perfectly.

The result I have managed to get so far with the ferrite RF choke looks like it might me a easy winner.

However I like your shield idea as well and that will be my plan 'B' mode of attack if necessary.

If these fail then it will be the Nelson fluro or an LED

The thought of that 20W 'mother' has given me ideas about recalcitrant grand children.

Whatever, I'll run a post about the outcome/s of Plan 'A' and/or 'B'.
FollowupID: 23254

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