LED masthead lights interfere with the AIS reception

Ashman

Ashman

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I've recently changed my tri-light filament bulb to a Boatlamps' tri-colour LED but I've noticed that when I switch it on all the AIS targets disappear off my chart plotter.

I'm using a Digital Yachts transponder via a splitter on a VHF antenna that is sited about 250mm from the led bulb. Other yachtsman have told me that my AIS transmissions are OK but its getting very irritating to turn off my tri-light every hour to see if other vessels are in range. I've now noticed my LED masthead anchor light is having the same effect.

I guess this might be a common problem but can anybody suggest a simple solution other than changing back to a conventional filament bulb or moving the antenna?

Apologies if this subject has already been done to death but I'm out in the Cape Verdes and megabytes are too expensive to permit much research!
 
Ashman said:
I've recently changed my tri-light filament bulb to a Boatlamps' tri-colour LED but I've noticed that when I switch it on all the AIS targets disappear off my chart plotter.

I'm using a Digital Yachts transponder via a splitter on a VHF antenna that is sited about 250mm from the led bulb. Other yachtsman have told me that my AIS transmissions are OK but its getting very irritating to turn off my tri-light every hour to see if other vessels are in range. I've now noticed my LED masthead anchor light is having the same effect.

I guess this might be a common problem but can anybody suggest a simple solution other than changing back to a conventional filament bulb or moving the antenna?

Apologies if this subject has already been done to death but I'm out in the Cape Verdes and megabytes are too expensive to permit much research!
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put a seperate aerial on the stern rail. mine picks up targets much further than i need & i have reduced the target list to 10 Nms
 
The problem is the power supply not the LED itself, although knowing this doesn't help you much. The buck-boost regulator in the light circuit controls the power supply to the LED and, depending on the type and the frequency at which it switches, can cause interference at vhf. You may find that you have problems with your vhf radio also if it shares the antenna located near the light.
Various fixes have been proposed - Orcagreen had a problem with this and they suggested using graphite beads fitted into the wiring to the lamp - I don't know if this would be the solution in your specific case.
Strangely, cheaper LED lamps that don't use Buck regulators don't have this same problem, and not all Buck regulators do - depends on the frequency at which they switch. Sorry I can't offer a solution. Others will be along to offer most positive solutions, I hope.
 
I can see this question coming up many more times this season.

The new ISAF Cat 2 requirements for offshore racing for 2014 state that the AIS antenna must be at the masthead. Bearing in mind that many races also require the transmission of AIS with a Class B transponder, I can only guess that in most cases a splitter will be required in order to share the masthead VHF antenna.

For this reason I am currently looking around at splitters and having to bear in mind that a number of LED light fittings do emit at frequencies that appear to interfere (and due to differing technologies in use in the splitters, some may suppress LED interference better). I have a LED tricolour and anchor light at the masthead already.

What make of splitter do you use? I currently have Vespermarine, Raymarine, Digital Yacht, Em-Trak, Comar, AMEC, Sevenstar, Easyplit and True Heading in my shortlist...
 
Hmm.. Been thinking a bit more about this and as Salty John says, if it is radiated interference (as it most likely is) from the power supply within the LED unit then any interference received by the antenna is not going to get filtered out by any splitter.

In fact the splitter should be passing everything through.. So perhaps the part of the LED unit with the high frequency power signals could be shielded better. Sounds like a task for the LED unit manufacturer.

My NASA Supernova combined tricolour/anchor light does not appear to affect radio reception although I think a bit more testing is now in order.

I will see what I can find in the way of interference at the weekend. None noticed so far but then I was not really looking for it.
 
Many thanks everybody for the responses, I'm going up the mast tomorrow to replace the bulb back to filament. We are crossing to Brazil in a week or so's time and probably will run the majority of nights without a tricolour to save power - risky I know but we'll keep a good watch and for most of the time there will be little shipping to concern us.
The splitter by the way is from Digital Yacht as well as the transponder.
 
Scotty_Tradewind said:
I know little on this subject but would it help to move the aerial away from the LED on an extension bar of some sort or is this 'interference' transmitted over a long distance. ?
Why not have a separate dedicated AIS aerial away from the masthead?

best of luck,
S.
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mine on the stern rail has picked up vessels @ 70 Nmls, exceptional i know guess high pressure @ the time
 
We've talked with several customers that have experienced RFI caused by LED masthead lights. The problem is switching noise within the marine band which is above the limits in the marine standards for this. A splitter likely won't help since the noise is within the band and so the splitter wouldn't be filtering it out.

The symptoms are often a high background noise level alert from the AIS unit (this alert is required by the latest Class B standard) and/or reduced target reception due to the noise level. We posted a technical note about it at http://tinyurl.com/mwx5kcy and you can find more info from Orca at http://ogmtechnical.blogspot.co.nz/2009/06/update-on-rf-interference-for-trianchor.html

If you've got one of our transponders, you can do a quick check.... on the AIS Status page it displays the RSSI on each channel. It's normal for it to fluctuate up and down. But if you switch your LED lights on and see the RSSI jump up and stay up, then you've got a noise source.
 
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My Advansea AIS transmitter also reports RSSI figures. I will disconnect it from the pushpit antenna at the weekend and connect it to the masthead antenna and see what difference is noted.
I will then reconnect the vhf radio and see if any audible noise received also changes (whilst listening to the AIS channels on the vhf) when the LED tricolour is switched on.
 
Just back on board. With the VHF (using the masthead antenna) I tuned it to listen on channel 87 and 88 in turn... AIS clicks hard clearly on each channel and no discernable noise difference heard when either the LED tricolour or the anchor light switched on..
Not a perfect test. We shall test in more depth at the weekend but it looks like the Nasa Supernova is relatively noise free.
 
Ashman said:
Many thanks everybody for the responses, I'm going up the mast tomorrow to replace the bulb back to filament. We are crossing to Brazil in a week or so's time and probably will run the majority of nights without a tricolour to save power - risky I know but we'll keep a good watch and for most of the time there will be little shipping to concern us.
The splitter by the way is from Digital Yacht as well as the transponder.
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Sounds like the best plan given the circumstances. And not really risky, there's next to nothing out there and anything you do come across will pick you up from ais or radar long before or even if visually . Anyway, you'll see them before they appear over the horizon.

Where in a Brazil are you looking to landfall? Jacare would get my vote.
Here's some pushpins might come in handy if you end up in Natal or Jacare.
https://maps.google.com/maps?hl=en&gl=gb&ui=maps

Enjoy :cool:
 
GHA said:
Sounds like the best plan given the circumstances. And not really risky, there's next to nothing out there and anything you do come across will pick you up from ais or radar long before or even if visually . Anyway, you'll see them before they appear over the horizon.

Where in a Brazil are you looking to landfall? Jacare would get my vote.
Here's some pushpins might come in handy if you end up in Natal or Jacare.
https://maps.google.com/maps?hl=en&gl=gb&ui=maps

Enjoy :cool:
Click to expand...

Thanks GHA
Salvador / Baia de Todos os Santos is the target but it will depend on the trade winds once we've crossed the equator.......I don't want to go closer than a beam reach for comfort!
 
By the way, the Optolamp (http://www.neptunes-gear.com/products/led-tri-color-masthead-light) has a different design power supply and produces no RF noise and no AIS interference. It's my 4th tricolor, as the first three (All major brands) all cut the AIS signal. The Opto is a very nice unit - they do have a couple models at different price points with fewer or more features (this link is to the fuller feature model).
 
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Out of interest..

What makes were the three (model and year) that did cause the interference?

When the lights were on, did you just not then have any AIS Rx or did your AIS receiver have an RSSI level indicator as indication?

Did these previous LED lights also cut your AIS transmission?
 
^^ I started with two LED replacement bulbs (one was a BAY 15D TRI-COLOUR MASTHEAD, can't remember what the other model was), tried Lopo and then aqual signal.

Generally, with all of them, my ais reception range was cut by 50%. I know my ais transmission range was cut (i tried flipping the led on and off one night passage when I had another boat on the radio) but don't know by exactly how much.

I am told that Lopo has redesigned and theri RF noise is now better, but the bigger problem with them is that their reliability sucks. I still use them for my deck nav lights and even with the newest models I am only getting about a year between failures. They are terrific about replacing them for free, but it is a pain when cruising.
 
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My arrangements are separate. Aqua-signal LED masthead tricolor, VHF Metz antenna on port side of masthead, about 15 inches out on a bar, same style bar on starboard side NASA AIS receiver again about 15 inches out on separate Metz antenna. Plotter is separate and below on internal antenna. Have not seen any adverse effects when switching the tricolor on and off.

NASA suggested there could be interference on AIS reception when VHF is on transmit but not too likely with the separation achieved. Still it would not be critical if such occurred. Also have VHF handheld and backup VHF with pushpit Metz antenna.

(All Metz from Salty John)
 
Hi Ashman, this is Paul from Digital Yacht and I have just read this interesting thread. I must admit that we have not had any direct contact from other customers about interference with LED Nav Lights, so I hope that it is not too common an occurrence. That said, I wanted to jump on this straight away and see if there was anything that can be done to fix the problem.

I have called Boat Lamps and spoke to Adrian the owner, who is also very interested in investigating and solving this problem. We have planned for him to send me a lamp with voltage regulator and then I will test it with our receivers and transponders. The goal is to try and recreate the problem and see if a fix can be found.

I am hoping to have my investigation sorted in 1-2 wks and I will post my findings on here as soon as complete.
 
It would be good if someone investigated this phenomenon - I thought it might be a good subject for a PBO/YM investigation to identify those LEDs that did interfere and those that didn't.

My own investigation leads me to the view that certain buck regulators with high switching speed, to reduce size and cost, are noisy and effect VHF reception and transmission.

This link takes you to a discussion on noise from a particular type of buck regulator:http://ww1.microchip.com/downloads/en/AppNotes/01466B.pdf

Manufacturers of masthead lights are aware of this problem and are, presumably, modifying their designs to use less intrusive regulators. Some don't use buck regulators for this reason, I think NASA might be one of those.
 
My latest update is that I have now installed a splitter near the chart table so the VHF and the AIS Class B transceiver share the same masthead antenna.

I don't appear to have any interference when the NASA masthead lights are used. AIS RSSI levels are unaltered and AIS TX and RX looks to be unaffected.

As others have said.. it is looking like certain LED power regulation circuits cause issues.. but if they are interfering at the AIS frequencies then they could just as easily be interfering at close to (or on) your channel 16 frequency.. Definitely worth further testing.
 
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