Disputed interference between LED masthead light and VHF antenna

[Karanga]

I went through this process too.

The surprising thing is almost every supplier will say that they have never heard of their LED replacement lights blocking AIS signals. I don't know if it is pure ignorance of the issue or head in the sand. So frustrating!

It was made worse for me cos I leave my anchor light on permanently (except when night sailing) . My rationale there is so little power consumed and I never have to remember to turn the light on in the evening. But then interference would be constant, not just at anchor, when AIS reception is obviously much less important.

I spoke to this guy, who indicated that most of the problem with "noisy" LEDs is from multi-voltage (usually 9-30 volts) lights. Truer 12v lights create less interference.

https://www.ledshoponline.com.au

Amazing difference in price from the usual chandlery Sam Allen marine supply at $85, which blocks the AIS to this online version that creates no interference and costs only $8. I ordered several (to have some spares). As soon as I fitted it, the AIS reception reverted to perfect.

Tim

[Joh.Ghurt]

Originally Posted by Karanga

I spoke to this guy, who indicated that most of the problem with "noisy" LEDs is from multi-voltage (usually 9-30 volts) lights. Truer 12v lights create less interference.

This makes a lot of sense. If the led includes a small step-up / step-down converter, these will work at high frequencies whose harmonics may affect VHF. Usually this kind of blame is laid on Chinese cheapo-ware, mostly for valid reasons.

[StoneCrab]

LED's run off of DC. Constant Current, Constant Voltage systems create AC at high frequencies and then rectify it back to DC for consumption by the LED. Where this is done would make a difference in your interference. If it is done at the masthead, right next to the antenna, your interference results would be expected.

I know you want the manufacturer to fix this problem but if you want to play around, try encasing the cavity with the CC/CV chips in it with copper foil tape. Solder a ground lead onto the tape and ground it to the mast. The faraday cage should ground the RF, keeping it away from the antenna. The modification could be done quickly with a trip up the mast. (I'd do my soldering at deck level and bring the tape and pigtail up).

Adding a ferrite bead or two to the power line may help as well. This would seem to be counter intuitive on a DC system, but RF radiates in all sorts of ways and you are trying to ground or modify the components that are radiating the interference. Ferrite beads can dampen the RF or change the resonant frequency. If you can get the interference resonance away from the VHF / AIS frequencies, it may be enough.

If you know a HAM with a spectrum analyzer, they would be able to actually see the results of the modifications at the masthead. A screen shot of the interference being generated by the tricolor LED's would be conclusive evidence for the manufacturer. This followed by a reading with the tape and ferrite bead modifications would show your progress.

The current limiting and voltage reduction can also be accomplished by the use of resistors, which do not create RF noise. The LED brightness cannot be guaranteed with just a resistor network driving the LED's.

Walworts and LED's really are the boogieman for radio communications at home and on ships.

[Happ]

Originally Posted by ahun

Good day,

I would appreciate your thoughts in this matter:

Installed new LED masthead light earlier this year:

TRICOMBO NAVIGATION BA15S - MARINELED

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.

I’m not an electrician so I’m looking at this from a common sense approach. If the Tricolor is good then I wonder if your connection isn’t’t good enough or the wire you are using is not tinned. Or is the antenna wire not shielded? Any of these could allow the leak in transmission from the Tricolor.

[betwys1]

Originally Posted by ahun

Good day,

I would appreciate your thoughts in this matter:

Installed new LED masthead light earlier this year:

TRICOMBO NAVIGATION BA15S - MARINELED

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.

The maker acknowleges fairly significant levels of VHF noise. Sadly, this means choosing a lightling system that does NOT feature RF interference.

[team karst]

The EMC madness is quite easily solved at the manufacturers level with an old school LM317 ic in constant current mode. There will be more heat generated to be dealt with. And it still needs to be tested for rf immunity. You dont want the ic going full on during vhf transmit condition. ThAt could mean instant led burnout.

[sailingbare]

Video log your own test. Show all the wiring and location of everything. Then demonstrate the problem. Since the FCC took all the teeth out anti-interference regulations, it's buyer beware. Let the company know that you will be publicizing your results with the world-wide cruising community. They will be more worried about losing sales than supposedly passing tests. (Normally a few units are tested. Very few companies test every individual unit they make.)

[aqfishing]

Originally Posted by 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?

Good point that I notice(unless I missed it) went unanswered.

@ahun, does to problem only occur when the light is on?

[hcfirstlight]

We added new LED TRI/combo and deck/steaming light this past spring (both Aquasignal). We also rewired with shielded wire to these lights. We use a separate VHF antennae for AIS. No interference at all to either VHF or to AIS. It certainly seems to be a faulty driver for that light.

[dmkkeng]

Originally Posted by hcfirstlight

We added new LED TRI/combo and deck/steaming light this past spring (both Aquasignal). We also rewired with shielded wire to these lights. We use a separate VHF antennae for AIS. No interference at all to either VHF or to AIS. It certainly seems to be a faulty driver for that light.

It is definitely possible the light could be defective, however rewiring with shielded cable likely significantly reduced the potential for interference. I assume the separate AIS antenna is not located near the light source wiring?

One other thought is the antenna connection - have you checked the reflected power on your main antenna, it is possible there is a problem with your antenna cable or connections. If they are good then perhaps try a filter on the existing light wiring or replace with shielded wiring. Good luck - let us know what your solution was.

[joehersey]

Originally Posted by ahun

Good day,

I would appreciate your thoughts in this matter:

Installed new LED masthead light earlier this year:

TRICOMBO NAVIGATION BA15S - MARINELED

It's claimed to have no interference with VHF or AIS frequencies. .....

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.

If you look at Annex C of EN60945 (actually IEC 60945), you see the emission limit that standard specifies for the band 156-165 MHz (24 dB µV/m at 9 kHz bandwidth, at 3m) is based upon the assumption that the interferer is separated at least 15m from the antenna. It assumes interference comes from the bridge of a ship, not from an LED mounted a meter or so from the antenna.

For the last two years, RTCM has been developing an EMC standard to address this problem, and hopes to have it out before summer of next year. To protect VHF and AIS antennas from LED lights mounted a meter from the antenna, RTCM found that the automotive EMC limits specified by CISPR 25 (15 dB µV/m at 120 kHz bandwidth, at 1m) to be needed to avoid interference.

RTCM and the USCG sponsored EMC testing of twenty-one lights this past year: eleven 2m nav lights, eight nav lights rated at 3nm and above, a spot light and a deck light. None of the 2nm nav lights tested were found to radiate anything at VHF, but all the the 3nm+ nav lights were found to radiate VHF noise. Although light sample #1 (a 6nm mast headlight) did radiated VHF noise, its level of interference was low, and would not cause interference to VHF or AIS. At first, light sample #8's (a 3nm sidelight) level of radiated interference seemed similarly low, but later tests showed it radiated lots of VHF interference conducted along its power leads. IEC 60945 does not test for conducted emissions at VHF.

USCG isn't allowing us to identify which manufacturer's lights were tested, or what their results were. Only generic descriptions could be released. Hopefully once RTCM is able to release its standard and manufacturers begin using it, it'll become more clear which lights have an EMC problem and which ones do not.



Joe Hersey
Chairman, RTCM SC137

[team karst]

Joe. How does the RTCM relate to IEC working groups? I do IEC safety and EMC design and test work in the industrial space; am not familiar with the marine side.

[joehersey]

Originally Posted by team karst

Joe. How does the RTCM relate to IEC working groups? I do IEC safety and EMC design and test work in the industrial space; am not familiar with the marine side.

RTCM has a close working relationship with IEC. Once this RTCM EMC standard is completed, it will go to IEC TC80 as a new work item there. 406 MHz EPIRB standards have been handled the same way.

IEC has two maritime TC's at IEC: TC18 (electrical) and TC80 (radio and navigation systems). RTCM has had a long standing Cat A Liaison relationship with IEC TC80.

[Bycrick]

The specified sensitivity of most VHF radios (including AIS) is well under 1 micro volt. So a device that emits 20 micro volts of noise is going to render the radio useless if located close to the antenna. Whether it meets some specification is irrelevant.

[joehersey]

Originally Posted by Bycrick

The specified sensitivity of most VHF radios (including AIS) is well under 1 micro volt. So a device that emits 20 micro volts of noise is going to render the radio useless if located close to the antenna. Whether it meets some specification is irrelevant.

Bycrick, micro volts into a radio receiver’s antenna connector and micro volts per meter field strength seen by an antenna are two very different things. VHF radio sensitivity is spec’d at 2 micro volts or -107 dBm, and AIS is similar, and noise must be kept about 10 dB below that. But the way EMC standards measure noise is a bit strange, so we couldn’t depend upon those specs alone. We measured actual installations against real lights, and came up with results very similar to those long used by the auto industry in protecting public safety VHF radios using bands similar to maritime from LEDs installed close to their antennas. 15 dB micro volts per meter field strength at one meter at 120 kHz bandwidth. A light emitting at or under that value cause no discernible loss of sensitivity to VHF radios or AIS. That’s a strict standard. But there are lights that meet it.