SailNet Community banner
1 - 11 of 11 Posts

·
Registered
Joined
·
100 Posts
Discussion Starter · #1 · (Edited)
I'm not sure if this has been posted before, but for anyone who hasn't heard, several LED manufacturers are skimping on the radio frequency interference suppression in LED lights. This could wipe out your VHF and AIS reception (you can still transmit - but you may not be able to receive). That is happening frequently enough that the Coast Guard is now warning mariners about the problem.

See the USCG safety alert for details about LED interference with AIS & VHF: https://www.dco.uscg.mil/Portals/9/...INV/Alerts/1318.pdf?ver=2018-08-16-091109-630.

The USCG procedure in that alert won't work with PLL-based receivers - like Standard Horizon's because the squelch will only open with a coherent carrier - not with random noise. It's better to tune in the weakest NOAA weather station, or some other weak station, and then turn on your LEDs - one at a time. If the NOAA station vanishes or is buried in noise, you have a noisy LED. I've been in contact with the USCG people who are investigating this problem and informed them that their test procedure won't work with all comms radios. I've also reported some tests to them.

This problem is especially bad if you have a noisy LED lamp near your antenna - like a bad tri-color at the masthead. But the RFI can radiate over the supply wires throughout the boat. Installations are so variable that defined countermeasures are impractical.

A little background: it's not the LED lamps themselves that are at fault, but rather the cause is the internal pulse duration switching power supplies - intended to allow the lamps to operate over wide voltage ranges. Those of you with a radio background will know about old spark-gap transmitters. They were outlawed because they broadcast across a wide RF spectrum. Well, these defective LEDs are doing the same thing. Since the lamps are usually encapsulated, the problem isn't field repairable. The only practical fix is for the manufacturer to reduce the slew rate of the switching supplies (which will make them slightly less efficient). More time in the switch transfer range = more power dissipated as heat.

This shouldn't besmirch all LEDs. After spending hours in a Faraday cage with a spectrum analyzer, I found that some are very quiet. I tested many lamps and found the ones with the European "CE" seal were generally the best. To get that seal, the lamps have to pass a lab test for RFI. Here in the US, it's the wild west. Caveat Emptor. The worst lamps I tested were the incandescent substitutes intended to fit in the incandescent lamp housing. Most were made in China, with no RFI test certifications. But many well-known brands made in the US were also noisy.

If you're sailing an untested boat, and you can't receive a station, turn off all your LED lamps. It may solve the problem (if you don't mind being in the dark with no navigation lights).

You might try RF chokes, shielded cables, parallel bypass capacitors, etc. But some of the RFI is radiating right off the lamp housing, and you may not have any appreciable success. I tested some lamps where covering the lamp in aluminum foil - but not shielding the supply wires - eliminated nearly all the noise: so all the noise was radiating from the housing. Until someone invents transparent aluminum, that won't be a solution for a lamp.

If it radiates RFI, return it, and report the make and model to the US Coast Guard: https://www.navcen.uscg.gov/?pageName=contactUs, regardless of whether you are in the US. They will appreciate the report. They are trying to compile a list of bad lamps and makers.

73
N8QH - out
 

·
Registered
Joined
·
1,129 Posts
A good number of LED's are coming in through offshore stores that ship LED products that were really not made to FCC standards and were never meant for distribution in this country which adds another wrinkle to things. Many who buy LED's factory direct from Asian or South American sources such as through EBay or Amazon could very well find that got something that will interfere with VHF, AIS, AM, FM, etc and even hard wired audio sources or computer devices powered by the electrical system on their boats.

It's become a growing problem since many people will only look at a price tag and don't consider whether the manufacturer of that bargain LED fixture the got shipped via China Mail, etc gave any thought to meeting regulations designed to prevent interference with radio or even hard wired audio or computer systems.

I remember some time ago the first smatterings of this were relevant to bargain Color Changing LED's that folks were putting on Pontoon and Deck Party boats that were interfering with the boats PA and Music Systems and later found out also caused problems with 2 way communications.

It can go beyond LED's too. In the GIS Skiff we had a sudden drop in accuracy from the Digitizer Boards and all sorts of issues with system lockups that drove us crazy until we asked if anyone had gotten any new devices that they were using in the work area. Someone had broken the power supply/charger for their MP3 player and bought a bargain replacement brick that did not have an FCC classification. Once we unplugged it all the issues went away and we were thankful that is was not a mass failure of a several hundred thousand dollars worth of specialized cartographic equipment. One could only imagine the potential errors some of these really bad/dirty devices could introduce to communication equipment, autopilots, depth sounders and nav stations.

Any new electronic accessory LED or not could cause interference with more than just radio communications if its poorly designed or not really made to be sold in the US or other countries with communication regulations regarding interference.
 

·
dadio917
Joined
·
345 Posts
"wiping out" VHF might be a bit of an overstatement. We have a LED tricolor on the mast maybe 6" from the VHF antennae. I tested it and sure enough had to turn up squelch a notch. but it certainly didn't wipe out our radio.

Still, I may have to update one of these days. low priority.
 

·
Registered
Contest 36s
Joined
·
7,771 Posts
Does proximity of the antenna and offending LED matter? Is there a distance that sub par LEDs have no impact?

So AIS is VHF and there is no acquisition time. You turn it on and all signals appear at targets.

Can one do a work around by turning the tricolor off and see signals appear and then back on again? Or is this simply blocking weaker distant signals?
 

·
Administrator
Beneteau 393
Joined
·
9,205 Posts
Can one do a work around by turning the tricolor off and see signals appear and then back on again? Or is this simply blocking weaker distant signals?
Yes. Its exactly what I do to test it. But it takes up to 6 minutes to get all ships transmitting. Its not instantaneous.

My masthead tricolour is only an emergency nav light. My main ones are at deck level. When I turn on the mast head nav lights they cut reception from 20nm to 10nm. Thats a substantial amount.

I cant tell how much it cuts my transmission. I have tried on many occasions to ask other cruisers and passing ship how far my AIS transmits but no one understands. I mast have extremely stupid friends.

Mark
 

·
Registered
Joined
·
1,129 Posts
Does proximity of the antenna and offending LED matter? Is there a distance that sub par LEDs have no impact?

So AIS is VHF and there is no acquisition time. You turn it on and all signals appear at targets.

Can one do a work around by turning the tricolor off and see signals appear and then back on again? Or is this simply blocking weaker distant signals?
The distance from the offending LED to your radio or antenna at which there is no impact is a tough one as the moderately offensive units may have a variable distance depending on how everything combined is setup on your boat while the totally off spec lights (and they could be the cockpit or cabin lights) can impact anything connected to your boats electrical system since besides RF interference they also can feed back into the 12 volt wiring. The really bad part of this is the horribly off spec ones can impact any digital device having the potential to make depth readings and nav data from electronic devices questionable even if they are not creating audible evidence of their interference.

In the case of the cartographers (digital map making) equipment loosing accuracy it was oscilloscope readings on the power coming into the equipment that caused us to go on the Witch Hunt for the offending device and there was no audible clue from any device creating audio in the area. We had to review all work done in that area back to the day the offending device was first plugged in. This had the potential to have cost us hundreds of thousands of dollars and possibly more especially if product had gone out and clients had suffered losses from it before we noticed the issue. Yes AC verses DC on a boat however power line interference can impact devices on both.

Yes shutting the lights off when your using you nav station, dept sounder, radio or AIS can stop the interference as long at the problematic lights do not have a power brick/digital controller that stays active even when the lights are not running.

There is no one cut and dry fits all answer from how this has been developing over the past year or so. Were the lights designed to meet FCC specs and slightly missed, way off FCC specs, not even meant to be sold in the US or just some cheapest of the cheap product (fakes made to look like name brands included here) where no real consideration aside from their lighting up the first few times you flipped the switch was given?

We could be looking at just the tip of an ice burg here.
 

·
Registered
Joined
·
152 Posts
A couple of years ago we replaced all of the 35-year-old incandescent dome lights in our saloon with LED dome lights. The bright lights made a huge improvement in the living conditions down below and the shiny stainless steel domes looked good, too. But within a year, we noticed that the lights were getting dimmer. Some of the individual LED elements are no longer lighting up. One light has failed completely. If I remove the lens and press on the circuit board, I can get some of the diodes to light up intermittently. Pretty disappointing considering the amount of money we spent on them. This lesson reinforces the OP's message that not all LED lights are created equal. I haven't noticed any issues with radio interference but I'd bet there is a correlation between RFI and poor product quality overall.

BTW, I can't remember off the top of my head who the manufacturer was but it was a brand-name, domestic supplier. We bought them from a vendor at the Miami Boat Show.
 

·
Registered
Joined
·
2,960 Posts
My LED bike headlight interferes with my wireless speedometer/odometer when it's in power-saving mode.

If the headlight is on full there's no problem. But if it's on one of the dimmer power-saving settings my speedo goes crazy. First it read 48mph, then 2mph, then 0mph, then back up to the 30s.

The light doesn't actually dim when it's in power-saving mode, it actually flicks on and off faster than the human eye can perceive. I don't know the exact hertz but it's faster than the human eye, but slow enough that it's visible on an iPhone in slo-mo mode.

Anyway, that flicking on and off generates enough RF buzz to mess things up.



Is it similar with these boat LEDs? Is it the power supply switching that's causing the interference?
 

·
Registered
Joined
·
100 Posts
Discussion Starter · #11 · (Edited)
Is it similar with these boat LEDs? Is it the power supply switching that's causing the interference?
Yes, it is similar, and you've given a good description of the root problem: rapid switching. In the case of marine LEDs designed for wide voltage ranges such as 10-30 volts (that's just an example range), there is a switching supply within the lamp assembly that varies its on and off duty cycle to adjust the voltage for the diodes. (I'm trying to not be too technical here - electrical engineers please forgive my brevity.) The didoes themselves do not create interference - the culprit is the internal switching supply. The rise and fall times of those switches can be only tens of nanoseconds, and that switching can produce wideband noise. Radio people traditionally call it "hash." The no-dim and wide-voltage-range "features" can (but don't have to) carry a price: noise.

There are ways to prevent that noise from being generated - there are quiet marine LED lamps available. The noisy LEDs are poorly/cheaply/carelessly designed, and possibly the design itself was never tested by the manufacturer for RFI in the VHF band. Some well-designed LEDs may also simply be defective as individual units. Until the market demands it, I doubt that any but the best manufactures test individual units for RFI. As others have noted here, the problem isn't limited to LEDs, any switching power supply can create RFI. But the problem, in general, is especially bad when you have to turn off your navigation lights to stop the interference, trading one navigation hazard (disrupted radio reception) for another (no navigation lights). Actually, what's worse is not knowing the interference is happening. The worst case scenario in my mind is a day sailor in distress, who seldom uses navigation lights, caught out at night who's not able to receive responses from the Coast Guard.

Analog power supplies could be used instead, but they would be inefficient and dissipate significant energy as heat, canceling at least some the low power consumption advantage of LEDs.
 
1 - 11 of 11 Posts
This is an older thread, you may not receive a response, and could be reviving an old thread. Please consider creating a new thread.
Top