Marine Safety alert, LED lights and VHF

[ohgary]

IF you have or are considering LED lights, might be a worthwhile read.

The U.S. Coast Guard has received reports from crews, ship owners, inspectors and other
mariners regarding poor reception on VHF frequencies used for radiotelephone, digital selective
calling (DSC) and automatic identification systems (AIS) when in the vicinity of light emitting diode
(LED) lighting on-board ships (e.g., navigation lights, searchlights and floodlights, interior and
exterior lights, adornment).


See https://www.dco.uscg.mil/Portals/9/D...-16-091109-630 for full alert.

[GRIT]

Thanks for that.
We're all LED, from interior to navigation lights, to deck lighting. VHF not yet installed, so we'll test it as soon as we can.

Cheers.
Paul.

[Suijin]

It’s been known for some time that many if not most “retrofit” LED bulbs (I.e. those you purchase to use in a fixture designed for incandescent bulbs) can cause interference. Many manufactures have addressed this problem, reportedly. However the test suggested in the linked article is interesting and something I’ll try.

I have a “native” LED masthead tricolor/tricolor right adjacent to my VHF antenna and have not had any issues with VHF or AIS reception but it might be degraded. We’ll see.

[a64pilot]

I’m not sure I understood their test, but I can tell you how we test for EMI / RFI on aircraft.
Pick an unused channel with the lights off, set squelch so that it is barely extinguished, then turn lights on, if squelch is broken, the lights are emitting in that frequency.
Test several frequencies to be sure, up and down the band, test all lights ideally one at a time, or at least one circuit at a time.

My “limo lights”as my kids call them are noisy, they are the cheap string LED’s and some EBay LEDs that I had that we’re bayonet style to replace my interior light bulbs were also noisy. I have since went with Marine Beam fixtures.
However I have been unable to detect my Marine Beam lights, and I have several of those, most NAV lights are Marine Beam. My Hella spreader lights are not noisy either, nor is my Aqua Signal tri-color. there seems to be a correlation with cheap being noisy.

[Suijin]

Originally Posted by a64pilot

I’m not sure I understood their test, but I can tell you how we test for EMI / RFI on aircraft.
Pick an unused channel with the lights off, set squelch so that it is barely extinguished, then turn lights on, if squelch is broken, the lights are emitting in that frequency.
Test several frequencies to be sure, up and down the band, test all lights ideally one at a time, or at least one circuit at a time.

That’s basically the test the USCG doc outlines, other than testing multiple frequencies.

I have a bunch of retrofit bulbs in the cabin but it did not occur to me that they might be an issue. I’ll run the test with them as well.

[er9]

i jst replaced my interior lighting with LED's. I havnt done the exterior lights yet. My vhf thats hardwired to my mast antenna is unaffected by the LED noise but my little hand held ICOM is degraded quite a bit when they are turned on.

[Wotname]

Originally Posted by a64pilot

I’m not sure I understood their test, but I can tell you how we test for EMI / RFI on aircraft.
Pick an unused channel with the lights off, set squelch so that it is barely extinguished, then turn lights on, if squelch is broken, the lights are emitting in that frequency.
Test several frequencies to be sure, up and down the band, test all lights ideally one at a time, or at least one circuit at a time.

......

Just be aware the aviation VHF uses AM (amplitude modulation) while marine VHF uses FM (frequency modulation). AM and FM react quite differently to EMI/RFI and as a generalisation, AM is far more susceptible to EMI/RFI.

This does't negate the value of the testing method that a64pilot refers to.

As an aside, some (many?) GPS antennas can shut down some aviation channels if the antennas are closely sited. A notch filter in the com coax fixes the issue.

[Nicholson58]

If you use cheap replacement bulbs, especially from automotive suppliers, you may be more likely to have issues. Proper LED bulbs use pulse width modulating current control PWM. The switching frequency must be above the frequency to cause radio interference. Try Maine Beam replacements https://store.marinebeam.com/?gclid=...gaAnGLEALw_wcB. There are many other quality replacements available but the cheap stuff is just that.

[a64pilot]

Originally Posted by Wotname

Just be aware the aviation VHF uses AM (amplitude modulation) while marine VHF uses FM (frequency modulation). AM and FM react quite differently to EMI/RFI and as a generalisation, AM is far more susceptible to EMI/RFI.

This does't negate the value of the testing method that a64pilot refers to.

As an aside, some (many?) GPS antennas can shut down some aviation channels if the antennas are closely sited. A notch filter in the com coax fixes the issue.

My Bendix King KX-155 if the Nav half was tuned to a specific frequency it would cause my Garmin handheld to lose all Satellites. This confused me as it was a receiver only, not a transmitter.

EMI / EMF testing flight tests your really looking at other systems not the radios, for instance the system used at Ft Ord to track vehicles would “get into” the Mux Bus on an AH-64 when transmitted and shut down the Fire Control Computer, but it did it so intermittently and only on some aircraft it was hard to pinpoint.
It seemed the 1553 Data Bus that was used wasn’t very well shielded.

Point being I guess it that it can be indiscriminate, meaning it can cause havoc one day on one freq, and tomorrow it won’t.

[Wild Cherry]

I have LED bulbs which have basically all degraded to worthless over a short time because I assume they do not like a voltage above 15, which my new AGM batteries are being charged at. This has just happened when on shore power with charger working and batteries over 15 volts. They were pretty cheap retro LED's I purchased somewhere on ebay.

[a64pilot]

Cheap LEDs die a quick death, my “limo”lights that we rarely use have many inop LEDs is each string. I ought to peel them off and throw them away, but the Wife likes them cause they are really bright and useful for when she is cleaning.

Good LEDs will accept usually voltage from say 10 to 30 VDC.

What kind of batteries are you charging at more than 15 V?

[Wild Cherry]

[QUOTE=a64pilot;2703246]Cheap LEDs die a quick death, my “limo”lights that we rarely use have many inop LEDs is each string. I ought to peel them off and throw them away, but the Wife likes them cause they are really bright and useful for when she is cleaning.

Good LEDs will accept usually voltage from say 10 to 30 VDC.

What kind of batteries are you charging at more than 15 V?[/QUOT

Thanks for that question it is something I have been pondering. The batteries are new Victron 220ah AGM's and my Dolphin charger has an internal charge setting you can choose. Because there is no AGM setting I have chosen the Optima and Maxima battery setting which takes the charge up to 15,5 volts for a while before floating at 13,8 volts. Absorbtion is 14,8 volts. Not sure if this is correct and I have not yet received a reply from the charger folks.

[trifan]

If I'm chasing a noise problem I borrow a spectrum analyzer and watch the noise floor. If it is for local signals, a paper clip antenna usually couples enough signal to see what's happening. Ok, so for those not so lucky as to have a friend with a $40.000 analyzer, disconnect the VHF antenna, put a paper clip into the center pin of the radio's antenna connector (DON'T TRANSMIT!!!!) and have someone some distance away send a signal (or tune into a beacon signal) and then switch on the LEDs and see if their signal either goes away or gets noisy. It's better if you have a variable attenuator but what boater has one of those in his kit? Anyway, basically you need to start off with a weak signal and see if the suspected noise source drowns it out when turned on. - Later ...

[Wild Cherry]

I've just ascertained from the Dolphin online users manual that AGM's require the same charge rate as Gel batteries i.e. 14,4 volts absorption and 13,8 volts float.

[a64pilot]

[QUOTE=Wild Cherry;2703271]

Originally Posted by a64pilot

Cheap LEDs die a quick death, my “limo”lights that we rarely use have many inop LEDs is each string. I ought to peel them off and throw them away, but the Wife likes them cause they are really bright and useful for when she is cleaning.



Good LEDs will accept usually voltage from say 10 to 30 VDC.



What kind of batteries are you charging at more than 15 V?[/QUOT



Thanks for that question it is something I have been pondering. The batteries are new Victron 220ah AGM's and my Dolphin charger has an internal charge setting you can choose. Because there is no AGM setting I have chosen the Optima and Maxima battery setting which takes the charge up to 15,5 volts for a while before floating at 13,8 volts. Absorbtion is 14,8 volts. Not sure if this is correct and I have not yet received a reply from the charger folks.

Usually good chargers may have set profiles, but often have also a way to set a custom profile. If yours does, I’d strongly suggest you seek out the correct voltages from your battery manufacturer and set it to those voltages. If not pick something that is closest, in particular if I was plugged into shorepower often, I wouldn’t want to float them too high.
I don’t know your batteries, but suspect that voltage is too high.
If it is, it may dry out your AGM’s and you can’t add water.