Disputed interference between LED masthead light and VHF antenna

[ahun]

Good day,

I would appreciate your thoughts in this matter:

Installed new LED masthead light earlier this year:

http://www.marineled.fr/en/navigation-lights/76-tricombo-navigation-bay15s.html

It's claimed to have no interference with VHF or AIS frequencies. We didn't have time to test it for prolonged period of time before we left on our long term cruise, it was doing what it was supposed to do (lit up) so I was happy with it. Unfortunately, it turns out it messes with both the radio and the AIS. The symptoms are clear. I emailed the supplier but they claim it shouldn't create any interference. I copy my and their email here to describe everything:

"Hello there,

We started to use the tricombo masthead light that I installed earlier this year, on our cruise down the remote West coast of Australia, and sadly we realized that it produces a serious interference with both of the VHF and the AIS systems.

When sailing at night and turning on the tricolour the AIS targets promptly disappear from the chart plotter's screen (testing proved especially definite at Port Headland with about 50 ships moving and anching around us). If we turn the light off they come back on the screen, so it definitely is the root of the problem.

When the anchor light is on, either on stand-by mode, or alight after dark the VHF radio can't be used as it constantly crackling with squelch noise and no setting will change that.

We have the VHF antenna and the Tricombo masthead light on the top of the mast but with a fairly big distance between them (about 500mm) and the antenna works with the radio and the AIS via a splitter. (Connecting the antenna directly to the VHF or the AIS doesn't rectify the situation.)

I'll await for your reply.

Thank you."

Their reply:

"Hello

Tricombo passed successfully the EN60945 marine norms concerning the EMC noise level for all electronic equipement on mast , with reduced noise level frm 54 to 30 dBμV/m on the 156-165MHZ marine VHF AIS range

The mode which is the higher in terms of EMC is the SOS mode where we push the power to 7W peak , but even at these power peaks we are under the 30db level.

We can send you the complete lab test

You are the first client encountering such problem .

We can send you a quick video test ( a more talking test ) where we put the Tricombo at 2cm from the antenna of an FM receiver ( 108MHZ so very close to 150-165 MHZ marine VHF ) and you will see that on a pure classic music reception, you don't listen any noice when we switch on the Tricombo .
You hardly listen a little something when we move to the SOS flash mode

There must be some boat electrical connection

Best regards"

I wonder if I missed something or there is any other possible explanation? Ultimately how to prove if their claim stands or not?

Thank you.

[BillKny]

"He said--- She said."

If you turn on their equipment and the radio stops working... that's all I need to know.

Cause -> effect.

The right answer from a supplier who really had faith in their product would have been, "Send us that back as soon as you can! We need to know what went wrong, we'll send you a new one right away."

The response, "It must be your fault." is not reassuring.

What did you have before? Any issues with that equipment?

[Lake-Effect]

Assuming it makes a noise in VHF reception, make an audio recording from the VHF while you switch the masthead light off and on. And/or make a video of the AIS targets disappearing/reappearing.

Their claimed acceptable interference spec might be legit, but you still might have received a defective unit.

You might have to remove the masthead light and demonstrate on a bench that it still interferes with a handheld VHF, so that they can't blame the wiring.

[wholybee]

That response is well prepared enough with enough technical mumbo-jumbo it is almost like they get many complaints and had it pre-written.

with reduced noise level frm 54 to 30 dBμV/m

So, it could have up to 30 dBuV/m of noise?

where we put the Tricombo at 2cm from the antenna of an FM receiver ( 108MHZ so very close to 150-165 MHZ marine VHF ) and you will see that on a pure classic music reception, you don't listen any noice when we switch on the Tricombo .

A useless test. An FM radio station uses a lot more bandwidth (creates a redundancy and clearer signal) and a lot more power (better signal to noise ratio). It takes quite a lot to interfere with an FM radio station. I wonder why they don't do that demonstration with a marine vhf radio.

Not sure what your recourse is. I would expect them to at least offer a replacement in case you have a defective unit. If it hasn't been too long and you used a credit card you could reverse the charge.

FWIW, I use a Dr LED bulb. It creates a _tiny_ amount of audible interference with the squelch turned off. I still see AIS targets from 30+nm, however.

[Spot]

Ahun,
Do you have deck-level lights to use in the meantime?

[ahun]

Originally Posted by BillKny

"

What did you have before? Any issues with that equipment?

Everything is brand new, light, antenna, wiring including coax cable professionally crimped, AIS unit, VHF radio etc.

[ahun]

Yes, we are able to keep moving due to a spare set of navigation light on the sides of the doghouse.

[Dsanduril]

We had the exact same results with a LunaSea tricolor, right down to the advertising as “no VHF/AIS EMI” and zero acceptance of an issue from the manufacturer (although they have since changed the design, I guess that says something). Every time we turned it on we lost AIS reception beyond very short range. Even worse, we went to an average transmit time of 5-10 minutes because the AIS believed the frequency was busy.

Unfortunately EN60945 is completely inadequate for protecting AIS/VHF reception on small boats, and that’s at 24dBuV/m (quasi-peak, 30 peak). The standard was written long ago and allows 54dBuV/m from 30Mhz to 1Ghz except only 24dBuV/m (tested at 3m range) in the marine VHF band (156-165Mhz). Your vendor might barely meet the standard at 30 if their measurement is peak.

But that’s really not even close, here’s an interesting paper that calculates the noise necessary to completely wipe out AIS reception at ~8-10dBuV/m with 1m separation between LED fixture and antenna. On our masts, where even getting your 0.5m separation is generally tough even that level is too high. Bottom line, the standards are completely inadequate (and IMO your vendor doesn’t actually meet them), but they give the light manufacturer a place to hang their hat and hide.

We need to be looking at devices with at least an order of magnitude lower EMI than allowed by the standard if we want LEDs colocated with our antennas.

[Nicholson58]

Following the link I arrive at a fixture and LED bulb.

These bulbs normally are PWM (pulse width modulated). The reason they can operate on a very wide voltage is that the control circuit switches the light on and off at a high frequency. The percent on/off time is managed to yield the proper required average forward current. In order for these to not bother a radio the switching frequency needs to be high enough to not be near the radio frequency. Also, there are suppression accommodations as well. I suspect the bulb is faulty or possibly poorly designed.

We have used many PWM replacements from Marine Beam and IMTRA without interference issues.

[Tehani]

I think you could fix it by putting an EMI filter inside the light housing, connected between the riser wire and the LED lamp.

[donradcliffe]

A continuing problem we had with tricolor bulbs. I learned to test them at deck level by turning them on near a handheld VHF before I put them up on top of the mast. I was not able to find one (even MarineBeam) that did not strongly break the squelch on the VHF. There was some supplier from Brazil that used linear power regulators instead of PWM, but I ran out of time before we could get one shipped in.

[ShawnMack]

I have a dumb question because I know there are some super smart EE folks on here.
I understand that they design the PWM circuit to cycle as fast as possible primarily for efficiency, I think. Could you not turn the frequency down to simply accept a lower overall efficiency but also not be as close to the radio spectrums we rely on? Or is the EMF just so powerful its specific frequency is irrelevant?

[Lake-Effect]

Originally Posted by ShawnMack

I have a dumb question because I know there are some super smart EE folks on here.
I understand that they design the PWM circuit to cycle as fast as possible primarily for efficiency, I think. Could you not turn the frequency down to simply accept a lower overall efficiency but also not be as close to the radio spectrums we rely on? Or is the EMF just so powerful its specific frequency is irrelevant?

Not a dumb question.

High frequency PWM uses smaller inductors and capacitors, which is a savings in cost and size... but even so, I think you'll find that most marine LEDs have a PWM frequency already under 1 MHz. The problem is that these are usually square or rectangular waves, which have tons of higher harmonics, and its the harmonics that are the usual source of RF interference. So the fix is good design that includes suppression of the higher harmonics, which only has marginal impact on efficiency.

Sometimes extra filtering (a series inductor and a parallel capacitor) at the LED fixture's DC in will reduce RF interference from the wiring, but on a masthead, with the trilight close to the VHF antenna, it might not make much of a difference if the LED assemblies themselves are radiating.

[MoodyS]

Try a 0.1microFarad capacitor across the supply to the lamp at the lamp holder, usually soaks up most of the shash.

[team karst]

THis is a job for mix 61 ferrite on the leads. I"m an EMC engineer, btw. Optimally, the design is solid, so, its not and likely many are not. Unlikely the "bulb" itself is radiating much, its too small. Its much more likely to be the wires. Yes, the legal spec is not good enough if the culprit and victims are within 10 feet or so.

Modern boats are a minefield of EMC issues. I have one.... still working the solar controller messing with my airband (am) radio. stubborn.