LED Noise?

[Paul Elliott]

zboss, I don't know if there is a reasonable solution, but I will be interested to see if other folks are having RFI issues with their OGM lights. How close is your antenna to the OGM light? Both up at the masthead? Do you know when your OGM light was manufactured?

There are a couple of threads running now about (among other things) LED noise. Unfortunately none of them have revealed a magic bullet.

If somebody wants to send me an OGM, or any other LED fixture, I can characterize the RFI and possibly suggest some band-aids.

[Paul Elliott]

Originally Posted by colemj

The tech guy at OGM told me they have traced it down to one or two specific models of VHF radios.

Mark

I know this is old information, but it's also a crap excuse. Some radios may (perhaps) be more susceptable to certain out of band noise, but this really isn't a radio problem.

[zboss]

I contacted MISEA group and they indicated issues with the the ICOM 400-600 series radios (I have a Garmin). As an initial conversation with them, I thought the response was sufficient but if I can't solve this issue I am hoping they will issue a refund on the light or issue a replacement non-LED MISEA tricolor instead.

They suggested that I check to see if the cables are coiled together at some point. A second suggestion was to make sure the antenna was placed at least 6-8 inches away, mine is 8 to 10 inches away, although I need to check the exact distance.

[Lake-Effect]

Originally Posted by Paul Elliott

I know this is old information, but it's also a crap excuse.

Seconding this. The manufacturers of LED masthead fixtures need to step up and source or produce a suitable low-RFI LED device. They can't just grab any old LED bulb off the shelf, then blame the radio.

[zboss]

Originally Posted by Lake-Effect

Seconding this. The manufacturers of LED masthead fixtures need to step up and source or produce a suitable low-RFI LED device. They can't just grab any old LED bulb off the shelf, then blame the radio.

I agree.. I also wonder how they can pass FCC muster.

[hellosailor]

"They can't just grab any old LED bulb off the shelf, then blame the radio. "
Bear in mind, no LED "bulb" causes any type of RFI. It is the power supply or other circuitry, not the LED itself, that is causing the RFI.
Depending on radio design, if the frequency of the components is or isn't the same as what affects any particular radio or other device, well, the interference may apply to one device and not the next.

"I also wonder how they can pass FCC muster. "
What muster? The FCC has no general regulation that says "You can't create interference". There are specifics for different devices in different scenarios, such as creating interference in a home or office environment, or interference with specific services. Creating interference to a marine radio (or other radio) when the antenna is two inches away....What rule does that violate?

[pbiJim]

Originally Posted by hellosailor

"I also wonder how they can pass FCC muster. "
What muster? The FCC has no general regulation that says "You can't create interference".....What rule does that violate?

I think that they are referring to the "FCC Part 15" rule (47 CFR 15). Subpart B could possibly apply here.

[pbiJim]

Some general suggestions for knocking down hash signals:

Use twisted pair wires, rather than straight run wires.

Use co-ax cable, rather than unshielded wire

Run wires inside of EMT, seal-tite or Greenfield

Have wires cross at a right angle, rather than running parallel to each other.

Do not coil excess wire

If you know what frequency the hash is at, then it is often possible to calculate proper values for capacitors & inductors so that you can fabricate a notch filter to effectively suppress the problem. The components for a notch filter are inexpensive. You just need to chose the correct values for it to work correctly.

[Paul Elliott]

Here are some EMI tests done by OGM, showing improvements to the emissions from one of their LED navlights:


Note that they are testing according to the EN60945 standard for marine navigation and communications equipment (link). This is similar in style to the FCC measurements I am familiar with.

I can't tell from their plots whether the low-level background noise is coming from their LED fixture, or is ambient noise. You can see where they have reduced the level of some noise spikes in the marine VHF band.

But this EMI standard, while better than nothing, is still no guarantee that there will be no interference. It's been a while since I have done these calculations (so I would welcome a double-check from someone), but the VHF band emissions limit of +30dBuV/m (measured at a 3 meter distance) still gives a signal that is 38dB stronger than the sensitivity of a typical VHF receiver. Now instead of 3 meters, place the LED fixture 100cm from the VHF antenna and the level could jump an additional 15dB.

Kudos to OGM for running these tests, but obviously we need a much more stringent emissions standard.

For those of you who want to check my math, I am assuming a VHF antenna with a gain of +3 dBi, a zero-loss cable, and a receiver sensitivity of 0.22 uV.

[Lake-Effect]

Originally Posted by hellosailor

"They can't just grab any old LED bulb off the shelf, then blame the radio. "
Bear in mind, no LED "bulb" causes any type of RFI. It is the power supply or other circuitry, not the LED itself, that is causing the RFI.

You're correct. I should have broadened out to mention "off the shelf" current regulator designs as well.

...Creating interference to a marine radio (or other radio) when the antenna is two inches away....What rule does that violate?

Common sense. At least 50% of sailboats have their VHF antenna on the masthead. There are a number of design choices that would minimize the RFI at marine VHF frequencies.

[hellosailor]

Jim-
Part15 can be a long-winded document but even in the case of regulated equipment (like a home router) if you complain to the FCC that it generates RFI, they'll tell you that's your problem, shut if off when there are complaints. And the maker doesn't have to do a thing. (BTDT, got the t-shirt.)

If an anchor light is regulated, if someone filed a complaint, I'd expect to find a similar barn-door-sized-loophole that came back to "so shut your anchor light".

An imperfect world, yes.

[zboss]

Originally Posted by hellosailor

Jim-
Part15 can be a long-winded document but even in the case of regulated equipment (like a home router) if you complain to the FCC that it generates RFI, they'll tell you that's your problem, shut if off when there are complaints. And the maker doesn't have to do a thing. (BTDT, got the t-shirt.)

If an anchor light is regulated, if someone filed a complaint, I'd expect to find a similar barn-door-sized-loophole that came back to "so shut your anchor light".

An imperfect world, yes.

I agree the bureaucracy is at odds with common sense. If I was in distress and someone on my vessel was not aware of the issue and tried to issue a distress call in 16 it would fail.

This has got to be illegal by some standard.

In the end... I am hoping the replacement MISEA Signalmate tricolor will solve the issue. However, I am then losing my strobe... which I really wanted.

[goboatingnow]

Originally Posted by zboss

I agree the bureaucracy is at odds with common sense. If I was in distress and someone on my vessel was not aware of the issue and tried to issue a distress call in 16 it would fail.

This has got to be illegal by some standard.

In the end... I am hoping the replacement MISEA Signalmate tricolor will solve the issue. However, I am then losing my strobe... which I really wanted.

Designing a switching power supply that can sit right next to a sensitive antenna is always going to be a difficult call. There may be no easy answer. But clearly neither the light or the antenna actually need to be there.

Dave

[DeepFrz]

What Dave says ^^ is absolutely correct. Actually having an anchor light at the masthead is, IMO, the worst place to put it. They get lost in the stars.

[hellosailor]

"This has got to be illegal by some standard."
Not on this planet.
It would violate various codes, like the US Uniform Commercial Code, as being "unfit for use in commerce" but that might not commonly apply to even US users. I'd call it unfit for use, since vessels anchoring in a designated "general anchorage" in the US may be required to keep both a VHF watch and an anchor light, and use of this light would endanger the VHF watch. Bottom line, if it bothers someone, send it back & make them eat it. If enough of them go back, they'll design a better one.