RF noise in 12 volt fluros.

Tuco

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.

Regards

Ken Robinson

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.
rgds
Gerry

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.

Keith

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!