Possible problem with LED lights on boats

Possible problem with LED lights on boats

Light Emitting Diodes (LEDs) are, in my humble opinion, one of the great inventions of the 21st Century.

Old fashioned incandescent light bulbs make light by using electricity to heat a thin piece of wire, known as a filament, white hot. Hot enough to glow white. But the filament also gets very hot, so hot you can burn yourself grasping an illuminated bulb. This heat simply wastes
electricity – the electricity isn’t making light, it’s making heat.

A diode is an electrical device that permits electricity to flow through it in one direction but not in the opposite direction. A commonplace example are the diodes in your car’s alternator that take the alternating-current (AC) electricity generated by the alternator (get it? alternating
current so it’s an “alternator”) into the direct current (DC) that’s needed to charge your car’s battery.

Light Emitting Diodes are the first cousins to your alternator’s diodes – but when current flows through them, they emit light. And only light – making them seven to ten times more efficient in terms of electricity usage versus incandescent lights for the same amount of light. What a great thing for boats, especially sailboats. Navigation lights illuminated for an entire overnight sail for what incandescent lamps would use for just a couple of hours. Or comfortable cabin illumination at anchor or at a dock without an electrical connection draining only a fraction of your boat’s battery’s charge.


The Coast Guard has, however, issued a warning to recreational boaters that some LEDs designed to work with your 12 volt lights may cause interference with your VHF radio and its friends such as AIS.

Why some LEDs also emit radio interference is not clear to me.  But as long as a year ago I saw (unconfirmed at the time) reports of interference generation. The culprits at that time appeared to be primarily “brand X” light bulbs or entire fixtures from Asia. 

How to determine if any LED lights aboard your boat are emitting radio interference? Simple: turn off all the lights (cabin, deck, navigation, whatever) on your boat. Turn on your VHF radio to an unused channel (for example, channel 6 or 9). If you have a handheld radio, follow the
same procedure with that, also. At a comfortable volume, turn down the Squelch control on the radio until you hear the hiss of background noise. Gently turn the Squelch up until the noise just disappears.

Now turn on your boat’s lights one-by-one. If you suddenly hear a rush of noise on your radio, that LED is emitting radio interference. You should replace it. And the Coast Guard requests that you report information on the lamp or light (make, model, where purchased) to them at a
specific web site.


The Coast Guard’s official notice can be found at TinyURL.com/LEDsonboats.

Luther Abel

Luther Abel

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