I have witnessed this firsthand recently. I installed a new AIS transceiver and tested it over several trips and it worked flawlessly. Before heading north I changed my masthead nav lights and anchor light. First night out I kept getting a message on my screen saying channel noise exceeded. The AIS contacted were in and out randomly. In the morning I called tech mate in Mooloolabah who first though I might have a problem with my VHF antennae but then as a last thought he asked if Id recently added LED lights. Of course I had and the next night I sailed with no masthead lights on and had zero problems. I've since got back to a normal bulb and had similar issue since. He said its the chinese LEDS, they have a frequency width that way exceeds all VHF channels.

No quite the same but,, energy coming from some large radio mast just over a km away from where I was anchored, had my LED mast deck light lit up and blinking like lights on a modem

Well I suppose if we are aware of a potential problem . If it becomes a real problem ,we can manage it .

Karsten said..

Trek said..
There are maximum radio noise emission levels for the power supply of the LEDs which actually generate the noise

Trek, you're obviously in the deep end with LEDs and radio tech so can you answer a couple of questions:

1) If the mast-top LED lamp only contains led bulbs, and the power regulator is remote inside the cabin, I assume that interference would not happen between the bare led bulbs and VHF /AIS antenna ?

2) If a DC-converter type regulator is used on a boat (not just for Leds, but any dc voltage conversion duties), and installed in an all-metal box (typically Aluminium), does that stop most (or all) of the RF interference it may generate?

Thanks

Re 1) that is most likely right. If the power regulator is good then no noise will come out of its output wires (going to the LEDs) or come out of the input wires (going to battery). ie. smooth battery type DC power will flow only. The electric and magnetic field noise that might be radiated by the Power Regulator is so far away the antenna wouldnt pick it up. If the power regulator was a poorly filtered one and the noise got out of the output it would go straight up the wires to the LEDs .

Re 2} Metal boxes can stop electric field noise getting from in to out or out to in. (AKA Faraday Cage). But they dont stop magnetic noise. A current flowing in a wire causes an electric field to appear and a magnetic field that mimic whatever signal is in the wire. (AKA antenna). Also big switching power supplies contain big inductors that generate excellent strong magnetic fields. The magnetic field radiation can be reduced a bit by making the inductor in the shape of a toroid. But the magnetic field will happily go through all the shielding and induce voltages everywhere in the wires on both sides creating the illusion that the shielding doesn't work. But It does for the electric field but not the magnetic field. Theres an alloy called Mu Metal that can kind of fix that but not very well.

Incidentally if simple resistors are used instead of switching regulators the whole LED noise issue goes away. But they waste power and get warm.

Karsten said..
Trek, thanks for your thorough answers.

Since you mentioned resistors, can I shoot a brief ancillary question - if one were to use diodes and/or zeners to drop DC voltage by a volt or two, are they capable of generating electrical interference ?

Nup, they are fine for that - except for LEDs. In that case you have to use resistors.