LEDs and VHF interference

webcraft

webcraft

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Eight years ago I replaced the anchor light bulb in our Aquasignal 80 with a 10W equivalent LED and it has performed brilliantly ever since.

Five years ago I replaced the 25W filament bulb in the tricolour section of the light with a 25W equivalent white LED from Ultraleds. I was quite happy with the light intensity, colour, sector cut-offs etc. but dismayed to discover that the bulb interfered with the VHF rendering it unuseable. I went back to a filament bulb.

(The 10W equivalent anchor LED does not interfere).

We still have the same radio. I would like to try fitting an LED again in the tricolour, but am worried that the same thing might happen.

Any thoughts?

- W
 
I believe the interference is caused by the voltage regulator that cuts the 12v down to something the LEDs can use (and also regulates the amount of current they draw). Some work by very rapidly switching on and off, so that on average the voltage is lower, and if they do this at VHF frequencies (or some harmonic?) then they interfere. It's not inherent to all LED lamps, and since the problem is well-known now any decent maker should avoid it.

For what it's worth, all my lights on board (navigation and cabin) are from Bebi, and I've not noticed any interference. I do get a little off the tillerpilot sometimes.

Pete
 
You could try adding a few small capacitors on the LED's supply.
Or changing the wiring to it to twisted pair.
Or maybe a high pass filter in the aerial downlead?

But switched mode regulators are the bane of radio.

Mobile phone chargers and Navtex often being particularly incompatible.
 
Interestingly some friends of mine who are partway through a trip to Australia (their boat is on the hard at Panama) told me a similar story.

In El Jadida (Morocco) they swapped their tricolour bulb for an LED one. Their dedicated AIS antenna is around 18 inches away from the tricolour. That night they had zero contacts on their NASA AIS box even though they could see the lights of big ships. In Lanzarote they investigated and found it was the LED bulb. A spare LED bulb of the same make and type caused the same problem. With the incandescent bulb the AIS worked perfectly.

They were in Crete when they related this story and couldn't remember the make and type of the LED bulbs, but it's worth testing AIS and VHF if you fit LED bulbs I think....
 
I have a Lopolite tri-white at my masthead. There's no interference with the VHF. I don't have anything else up there except a wind-speed transponder to be affected.
 
The trouble is, just because one bulb is good or bad on one yacht, you cannot guarantee you will get the same results on any other yacht.

Possibly the best way forward would be a linear regulator for the LED's, which might be a bit more inefficient, particularly when the volts are high, but then you can afford the inefficiency when the engine is running.
A linear current source regulator might be 70% efficient while a switch mode might be 90% or even 95%, so the current saved over a 'real' bulb might be 60% instead of 75%.
The trouble is, it's easier to use the circuits widely used in mobile phones, cars, PCs etc than to design and build a unit specially for boats.

Of course putting such a circuit right next to the aerial and powering it with a cable running parallel to the downlead is not very bright.
 
webcraft said:
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Eight years ago I replaced the anchor light bulb in our Aquasignal 80 with a 10W equivalent LED and it has performed brilliantly ever since.

Five years ago I replaced the 25W filament bulb in the tricolour section of the light with a 25W equivalent white LED from Ultraleds. I was quite happy with the light intensity, colour, sector cut-offs etc. but dismayed to discover that the bulb interfered with the VHF rendering it unuseable. I went back to a filament bulb.

(The 10W equivalent anchor LED does not interfere).

We still have the same radio. I would like to try fitting an LED again in the tricolour, but am worried that the same thing might happen.

Any thoughts?

- W
Click to expand...

Odd. I have replaced my tricolour with an led from UltraLeds and no problems with the VHF.

It has to be down to the current control electronics in your led assembly.
 
Topcat47 said:
I have a Lopolite tri-white at my masthead. There's no interference with the VHF. I don't have anything else up there except a wind-speed transponder to be affected.
Click to expand...

Same here, no probs with a lopo light. Also the bedazzled cabin lights are clean. The florescent was a noisy bugg"r on HF.

Could you take a handheld into the shop to check before buying?
 
I had an interior bulb which caused interferance with my FM radio. Perhaps you could check at deck level before taking it up the mast in a similar fashion?
 
The Ultraleds LEDs in my masthead tricolour and anchor light have never caused any interference but a couple of the Searolf G4 LEDs in my cabin lamps caused considerable interference to vhf, both marine and broadcast. I cured this by soldering a 1000pf capacitor across the input pins and putting a ferrite sleeve on one of the power supply wires close to the bulb. Total cost only a few pence per bulb and cure complete.
 
I presume the "regulator" is integrated withe the LED "bulb", so no practical to attempt to replace the switching regulator with a linear one. Also, rather than the step-down (reduce the voltage) regulator suggested by earlier posters, it may well be a step-up regulator, allowing several LED chips wired in series as this format is more efficient.

Anyway, about the only thing you can do with it is filter out the interferance - as close to the LED as possible. Try soldering a ceramic capacitor directly across the terminals - keep the leads as short as you can, the capacitor value isn't too critical, but something around 100nF (= 0.1uF) would do the trick and can be found in any electronics technician's odds bin (or buy from maplin, etc.). Another thing to look for would be a small ferrite ring, designed for suppression jobs like this (might try Maplin, but definitely RS) - just thread both of the wires to the LED (again, as close to the LED as you can) through the ring a couple of times.

Hope this helps!
 
For VHF suppression 100nF is a bit big. I'd go for 1nF or maybe 10nF (1000 or 10,000pF). As said VERY short leads and feritte beads on the leads. 100nF should certainly help and be necessary for HF and MF/medium wave.

I'll be checking mine in the winter when I install LEDs with the mast down and using VHF broadcast radio and marine portable. Might even find a shortwave portable as well to try out.
 
I suspect this is more a supply decoupling problem than an RF interference problem. This is very common when you have a switching circuit on the end of long supply wires. As has been said it is very simple to cure with a capacitor as close as possible to the switching device (which effectively supplies the device with power during its switching operations.)
 
Nick, are you dropping your mast this winter? If so I could fit suppression components for you at some time mutually convenient. I really don't fancy trying to fiddle about with wee bits and pieces at the top of the mast though.

If not then I think it's a web search to get a new bulb from a manufacturer that makes believable claims about the RF immunisation of his products. I've heard good things about Bebi, but haven't used them myself. As you've seen in the discussion here it's very difficult since some report no trouble with a particular bulb that gives others grief. I would be looking for a manufacturer's commitment to a money back return if the new bulb doesn't cure the problem. There have been earlier threads reporting poor customer service from Ultraleds, but this might not reflect how they currently operate.
 
DaveS said:
Nick, are you dropping your mast this winter? If so I could fit suppression components for you at some time mutually convenient. I really don't fancy trying to fiddle about with wee bits and pieces at the top of the mast though.

If not then I think it's a web search to get a new bulb from a manufacturer that makes believable claims about the RF immunisation of his products. I've heard good things about Bebi, but haven't used them myself. As you've seen in the discussion here it's very difficult since some report no trouble with a particular bulb that gives others grief. I would be looking for a manufacturer's commitment to a money back return if the new bulb doesn't cure the problem. There have been earlier threads reporting poor customer service from Ultraleds, but this might not reflect how they currently operate.
Click to expand...

Hi Dave,

We are coming ashore in Balvicar this Winter and will be dropping the mast, so if your kind offer could be fitted in with a wee dramming session at some point that would be great. Mi casa es su casa.

- W
 
The LEDs with 9-30volt specs will almost certainly have switching circuits built in to control the current or voltage.
Those with 12 volt specs might have a switching circuit, especially those that highlight that the light output is controlled across varying voltages. Boat '12volts' can easily vary between 10 and 15 volts
The supply cable acts as an aerial for the fast switching pulses and happily radiate them across MF, HF and VHF.
The capacitors and ferrite beads mounted at the LEDs reduce the pulse sizes and bandwidth in the cables and so reduce the radiated interference.
 
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