Disputed interference between LED masthead light and VHF antenna

[goboatingnow]

Originally Posted by team karst

Not reading much here that is correct. Freq content of sq waves are odd harmonics.
The actual device making trouble is the switching fet in the power supply. But, critically, that is not the device radiating. And definitely not the leds, either.
Whats happening is the wires are subjected to rapidly changing currents. In other contexts, they are called antennas.

Correct , actual direct radiation from the electronics is likely to be low , the wires are big antennas. Focus your efforts on the power leads

[Dsanduril]

I feel the real problem is the controller in the light fixtures/bulbs themselves. All of the suggestions here are workarounds for a poor design. Manufacturer's do this because the one thing that kills LEDs faster than anything else is inconsistent voltage (actually inconsistent current, but that is a result of voltage changes). And putting the voltage/current control in the light makes them easy to install (with all the downfalls that brings, as exemplified in this thread).

I'd welcome a manufacturer that provided a well-shielded and choked power supply (could be wide input), at say 10.1V that could be mounted anywhere on the boat and paired those with LEDs designed to operate at the same voltage (say 10V). Properly designed the lights don't need PWM or dropping resistors, and by centralizing the source of the EMI you only have one location to manage/control. Given the low current draw of LEDs even up a mast you won't need too much wire capability to limit voltage drop between supply and consumption. If you used to have an incandescent up there you can probably keep the same wires and still be ahead on the voltage drop.

A sailor can dream...

[Jammer]

[QUOTE=team karst;3483471]Exasperated by running the radio coax and 12v lamp wires in parallel for 50 feet[emoji30]


It shouldn't matter with good coax and proper common-mode choking of the antenna system. Half a dozen ferrites around the coax near the antenna might help.

[Jammer]

Originally Posted by Dsanduril

I feel the real problem is the controller in the light fixtures/bulbs themselves. All of the suggestions here are workarounds for a poor design. Manufacturer's do this because the one thing that kills LEDs faster than anything else is inconsistent voltage (actually inconsistent current, but that is a result of voltage changes). And putting the voltage/current control in the light makes them easy to install (with all the downfalls that brings, as exemplified in this thread).

I'd welcome a manufacturer that provided a well-shielded and choked power supply (could be wide input), at say 10.1V that could be mounted anywhere on the boat and paired those with LEDs designed to operate at the same voltage (say 10V). Properly designed the lights don't need PWM or dropping resistors, and by centralizing the source of the EMI you only have one location to manage/control. Given the low current draw of LEDs even up a mast you won't need too much wire capability to limit voltage drop between supply and consumption. If you used to have an incandescent up there you can probably keep the same wires and still be ahead on the voltage drop.

A sailor can dream...

In EE circles we like to think about "electromagnetic compatibility" rather than ascribing blame solely to a device that produces interference, a device that is susceptible to interference, or an installation that is conducive to interference between two particular devices. In this light the VHF feedline should be properly choked, the antenna should be as far away as practicable from the light, and the light should have proper filtering.

Another possibility to consider (in combination with others) is to use a twisted pair (or twisted triplex, if there's a single return and separate supplies for anchor and tricolor) to deliver power to the LED assembly, rather than the usual boat cable. Twisted pair is much less likely to radiate.

Most LED lights use PWM because it is more efficient than regulating the steady-state DC current using linear techniques. You can build a really quiet LED that way but it will run hot and use more power.

The LED devices themselves (the actual light emitting diode, not the complete fixture) are low-impedance and require a current source rather than a voltage source. Sure you can put those electronics somewhere else but it complicates installation and troubleshooting. Now you have wires going up the mast that aren't just 12/24v dc (that can be tested and checked with a meter) but rather are somewhat lower and current limited. And now you have the LED controller that you have to find a place for, and it needs a housing and connectors which drive up the cost.

[Lake-Effect]

Originally Posted by Jammer

In EE circles we like to think about "electromagnetic compatibility" rather than ascribing blame solely to a device that produces interference, a device that is susceptible to interference, or an installation that is conducive to interference between two particular devices. In this light the VHF feedline should be properly choked, the antenna should be as far away as practicable from the light, and the light should have proper filtering.

Yeahhhh, maybe....and we're all grateful for the expert suggestions from you and others... but hey... 99 out of a hundred masthead light installations will have a VHF antenna within a foot or two of it, so one would expect they would design for that situation, (including that of the owner who's replacing an old-school tricolour) and the average boat owner or installer should expect that if installed competently, there will be no interference, and no voodoo required.

To go at this from a different direction, can anyone recommend an LED tricolour masthead light that didn't cause VHF/AIS interference for them?

[team karst]

[QUOTE=Jammer;3483735]

Originally Posted by team karst

Exasperated by running the radio coax and 12v lamp wires in parallel for 50 feet[emoji30]


It shouldn't matter with good coax and proper common-mode choking of the antenna system. Half a dozen ferrites around the coax near the antenna might help.

I’m thinking the same thing. Same ferrite for each device. Will not hurt and might help.

[wholybee]

Originally Posted by team karst

Not reading much here that is correct. Freq content of sq waves are odd harmonics.
The actual device making trouble is the switching fet in the power supply. But, critically, that is not the device radiating. And definitely not the leds, either.
Whats happening is the wires are subjected to rapidly changing currents. In other contexts, they are called antennas.

Thank you for the corrections.

So, if it is indeed the power wires radiating...
There must be about 100db of isolation between the antenna and the power wires inside the mast. Both antennas being stacked vertically, and the power leads being inside the mast itself.

So then, the interference would be from power leads to the coax. Decent coax installed properly should be immune from that. What coax is the OP using? If it is RG-8x then that could be the issue, it needs to be upgraded to something decent. Or, maybe a poor connection of the shield at the TX end?

Failing that, an LC low pass filter at the base of the LED bulb?

[wholybee]

Originally Posted by Lake-Effect

Yeahhhh, maybe....and we're all grateful for the expert suggestions from you and others... but hey... 99 out of a hundred masthead light installations will have a VHF antenna within a foot or two of it, so one would expect they would design for that situation, (including that of the owner who's replacing an old-school tricolour) and the average boat owner or installer should expect that if installed competently, there will be no interference, and no voodoo required.

To go at this from a different direction, can anyone recommend an LED tricolour masthead light that didn't cause VHF/AIS interference for them?

I have been using Dr. LED bulbs a for years with no interference issues. The ones that replace a halogen bulb. I do also have LMR-400 coax though. So if the interference is from the power leads run next to the coax, the LMR-400 might be what makes it work.

[team karst]

Yes on the LC filter. Ferrite is a lossy (good) L.

There is an unfavorable feedline/antenna affect called commonmode radiation. Its where the shield current is NOT the same magnitude as the center wire current. Its out of balance. It physically exists on the outside surface of the shield. It causes both radiation directly from the shield. And, in receive mode, it allows pickup also. Fix is to block the CM current with a choke in the feedline.

Wow, thought this was a sailing forum. [emoji122]

And then there is coax shielding effectiveness. Unrelated to CM issue. And its no where near 100db.

Re: LM400 and similar. Great coax, i use it, but u sure better keep it dry and non salty. It will rot the thin Al in pretty short order. There are better picks avail.

[ahun]

The coax cable is LMR-195, 50ohm, professionally crimped only at the two ends, continuous from antenna to splitter.

https://www.timesmicrowave.com/Produ...LMR%C2%AE-195/

[Jammer]

Originally Posted by Lake-Effect

To go at this from a different direction, can anyone recommend an LED tricolour masthead light that didn't cause VHF/AIS interference for them?

Here you go.


Otherwise interference has been a problem for radio reception since 1887. Choose any period in history, LORAN used to be sensitive to basically anything, 1960s before the semiconductor era generators were electrically noisy because of the commutator, HF was far more sensitive than VHF, etc etc.


I have an Aqua-signal anchor light that's LED that doesn't interfere with my VHF antenna, but my VHF antenna has a built-in choke that protects the feedline from picking up hash from the power cable to the LED, and, electrically, it's a couple of feet above the anchor light.

[Jammer]

Originally Posted by ahun

The coax cable is LMR-195, 50ohm, professionally crimped only at the two ends, continuous from antenna to splitter.

https://www.timesmicrowave.com/Produ...LMR%C2%AE-195/

You could try putting some ferrite chokes on it, near the antenna.

[Lake-Effect]

Originally Posted by Jammer

Here you go.

Otherwise interference has been a problem for radio reception since 1887.

I have an Aqua-signal anchor light that's LED that doesn't interfere with my VHF antenna, but my VHF antenna has a built-in choke that protects the feedline from picking up hash from the power cable to the LED, and, electrically, it's a couple of feet above the anchor light.

I don't recall too many DC-powered incandescent bulbs causing RFI.

It's possible to design an efficient LED constant-current drive that doesn't barf out so much hash... but some manufacturers of marine LED fixtures can't (or won't) do it.

(And don't get me started on "25-year" household LED bulbs that crap out in under a year. )

[Jim Cate]

FWII the anchor light "bulb" from Bedazzled (UK) causes zero interference with VHF/AIS, both serviced by a single antenna only a few cm away from the light. Quite bright, internal daylight sensor for auto switching, many connector options.

I've had very good service from those chaps and use their products in nearly all of our LED applications on board (and have for quite a few years now). It was Dockhead who suggested them as a source, and it was good advice for a cruiser outside of the USA.

Jim

[team karst]

Got my curiosity up on this. I have a led anchor lamp less than a foot away from the vhf marine at the masthead. The bicolor is at the bow. Coax looks pretty crummy 1/4” variety.
New to me boat, and i dont know who made the lamp. With a scan of 6 weather channels, some of which had marginal copy, and ch 9 and 16 set for squelch threshold, zero lamp affect on signals. I suspect the led was a retrofit, but dont know for sure. Some day, i will get up there and see what it is. A PO was German and there are a number of euro led retrofits inside.
Note that it is possible to get a narrow band interference at discrete channels, and conversely, possible to get wide band interference.