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post #7 of Old 03-14-2012
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Re: FM stereo interfence, Sensibulb LEDs and 12V Jacks

Phone chargers are some LED control circuitry are digital circuits these days, and they can make noise. If the noise if RFI, radio frequency interference that is broadcast through the air, that's hard to stop. If it is EMI, electromagnetic interference that is being carried out on the power lines, it can be easily filtered out.

Simplest way to tell which it is, is to bring another battery powered FM radio into the boat. Since that is not connected to the same power leads, it will have no problem if the interference is EMI. In which case you put noise filters on the radio's power branch, and on the ones to the charger and cabin lights as well. Those filters can be simple "noise filters" that you pick up at an auto stereo shop, or sometimes just 10mF capacitors will do the job well enough. (25c or so each?)

If the separate radio stills gets interference, it is RFI and you have to stop that at the source. A better charger and different lights might be called for, or moving the FM radios antenna further away from those noise sources.
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