Disputed interference between LED masthead light and VHF antenna

[Bycrick]

You got me. When I wrote the post, I thought about trying to be engineering accurate. I even had a comment about apples and oranges which I cut out during editing. You, of course, are right. My point was that a manufacturer dangling the "we meet ISO standard xxxxxxx" may be absolutely correct , but the device isn’t fit for the intended purpose. I once saw an ad for an aneroid barometer which proudly claimed to meet MIL-Spec XXX. When I looked it up, the spec said you had to be able to drop it some distance without damage.

[joehersey]

Originally Posted by Bycrick

….My point was that a manufacturer dangling the "we meet ISO standard xxxxxxx" may be absolutely correct , but the device isn’t fit for the intended purpose. I once saw an ad for an aneroid barometer which proudly claimed to meet MIL-Spec XXX. When I looked it up, the spec said you had to be able to drop it some distance without damage.

Bycrick, right on!

People expressed surprise when they discovered IEC 60945 (maritime) and CISPR 15 (lighting)-compliant lights causing severe interference. Yet when you look at those EMC standards, neither were intended to cover interferers so close to antennas. 60945 assumed 15m, and CISPR 15 assumed more. That’s why we discovered we needed a standard good to 1m separation.

[StoneCrab]

If your power wires are run up to the tricolor inside of the mast, they are in effect shielded by the mast assuming it is an aluminum mast. If your tricolor is mounted directly to the top of the mast, with the wires never seeing the light of day, your wiring is pretty protected from RF radiation.

On the other hand, if you have a drip loop exiting the top of the mast and heading over to the light it will probably be 6 to 20 inches long. A VHF antenna is about 19.25 inches long, so this wire can efficiently radiate in the VHF range and at harmonics above and below.

Ferrite cores, additional grounding and shielding the base of the lamp can all help.