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Old 17-02-2014, 03:03   #1
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Join Date: Oct 2011
Location: Lake Macquarie, Australia
Boat: Hunter 44DS
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Radio Interference

Just installed a new icom commander mic at my helm and discovered that when I turn to channel 73 it shows busy and there is a humming noise. I have discovered that when I switch my anchor light on the interference stops. Also I discovered a month earlier that when anchored in an area with weak TV reception we loose reception when switching on the anchor light. I think there is an LED light in the anchor light as I found a spare on onboard. Any suggestions on why this would be occurring? I did have the mast removed several months ago after purchasing the yacht when the rigging was done. Could the polarity of the light be wrong?
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Old 17-02-2014, 03:51   #2
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Boat: Valiant 42
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Re: Radio Interference

This is a common problem with LED lights. The problem is most likely at the mast head and it's possible there is nothing you can do about it. You should determine the exact model of light and date of purchase. Check with previous owner or your broker and maybe they can tell you that info. Then search the web for that light model and interference issues. Several brands are well known for generating interference. A few have been remedied by installing filters at the mast head but that often does not work. It's a design issue with the current regulator inside the light.

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Old 17-02-2014, 08:53   #3
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Re: Radio Interference

There are some LED anchor / tricolor lights that do not generate any interference. It depends on the type of regulator used to drive the LEDs; a switching regulator can be noisy, while a linear regulator will be silent.

I've got an "Amazonia" tricolor/anchor light from Optolamp (Optolamp - Optolamp - Signalization), and while located right next to my VHF antenna it creates zero measurable interference. I am 99% certain that the Amazonia uses a quiet linear regulator, and while I haven't tested it I assume that their anchor light does too.

Another option is the upcoming "FrankenBebi" anchor light, being designed and built as an open-source project: FrankenBebi Project - Home. This has been discussed here on Cruisers Forum. I can personally guarantee that this anchor light will be radio-silent, since I designed the circuit.

Of course an old fashioned incandescent bulb anchor light will generate no interference, but it sure burns a lot of amp-hours.

It is possible that you will be able to reduce the interference from your current light by soldering some filter capacitors to the power connection right at the light, and perhaps putting ferrites on the power leads. I suspect that this will not make much of an improvement if the light and antenna are co-located.
Paul Elliott, S/V VALIS - Pacific Seacraft 44 #16 - Friday Harbor, WA
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