Radio Interference From LED Lights

[k0ua]

I put a couple ferite cores on my LED light bars & radio power wires. It helped a bit on one (the least noisy one to start with), but not much on others.

It can't hurt to try, but don't count on it. Read up on HAM radio & RFI, it can be an insanely deep subject. I have my HAM radio extra license & still only get a bit of it.

Keep in mind there are several factors not stated in these scenario's. What is the mix of the snap on ferrites and what is the frequency of interest? Ferrites come in "mixes". Mix 28 to mix 61 are common mixes of ferrites used for these purposes. with the lower numbers more effective at lower frequencies and the higher numbers more effective at higher frequencies. In other words, if you have a problem with interference with your weather radio at a frequency at 162 Mhz you would be more interested in obtaining a mix 61 ferrite. But wait there is more!. When you snap on a ferrite over a wire, the closer the ferrite is to the wire, in other words the tighter the fit, the more effective it is. But wait there is more! If you can put multiple turns thru the ferrite, the effectiveness increases by the square of the number of turns. In other words, two turns thru the ferrite is 4 times as effective. But wait there is more!. The stinking cheap snap on ferrites that come from China, rarely ever tell you what mix they are. It is the luck of the draw, you don't know what you are going to get.. Also closed torroid ferrites are very much more effective if you can get the ends of the wire wrapped thru them. So they are not as convenient to use. But they are way more effective.

 

[k0ua]

Also don't forget about the efficiency of using bypass capacitors of the proper voltage rating and type to suppress RFI emissions from devices. Of course this requires opening up and soldering in a capacitor at the proper location. This is probably beyond the experience level of most users.

 

[Fallon]

Keep in mind there are several factors not stated in these scenario's. What is the mix of the snap on ferrites and what is the frequency of interest? Ferrites come in "mixes". Mix 28 to mix 61 are common mixes of ferrites used for these purposes. with the lower numbers more effective at lower frequencies and the higher numbers more effective at higher frequencies. In other words, if you have a problem with interference with your weather radio at a frequency at 162 Mhz you would be more interested in obtaining a mix 61 ferrite. But wait there is more!. When you snap on a ferrite over a wire, the closer the ferrite is to the wire, in other words the tighter the fit, the more effective it is. But wait there is more! If you can put multiple turns thru the ferrite, the effectiveness increases by the square of the number of turns. In other words, two turns thru the ferrite is 4 times as effective. But wait there is more!. The stinking cheap snap on ferrites that come from China, rarely ever tell you what mix they are. It is the luck of the draw, you don't know what you are going to get.. Also closed torroid ferrites are very much more effective if you can get the ends of the wire wrapped thru them. So they are not as convenient to use. But they are way more effective.

I'm aware of this. I got the mix that targeted close to FM frequencies (don't remember the number offhand). All clip on ferites had 2 wraps through them. I had 1 snap on & 1 toroid on each wire. I did my due diligence, at least a few hours of research. Like I said, deep rabithole to go down.

 

[DieselBound]

Not that this is going to help the OP, but I've read that CREE LEDs tend to not cause RF problems. I don't have any, so I am unable to vouch.

 

[Fallon]

Not that this is going to help the OP, but I've read that CREE LEDs tend to not cause RF problems. I don't have any, so I am unable to vouch.

LEDs don't cause any interference at all, even low quality ones. It's ALWAYS the power supply. The nature of how the power supplies work cause the RFI.

Cree does make some of the higher quality LEDs though.

 

[DieselBound]

Is it, then, the power supplies that are used for CREE lights? Is there a special pairing, or can anyone use crappy power supplies on CREE lights as well?

 

[vvanders]

Is it, then, the power supplies that are used for CREE lights? Is there a special pairing, or can anyone use crappy power supplies on CREE lights as well?

LEDs are pretty tolerant of any power supply as long it doesn't go overvoltage. The problem with cheap power supplies is they aren't designed right and don't use the correct filtering.

A switched mode power supply looks a lot like a radio transmitter. They charge up a bunch of current and dump it, usually at a fixed frequency. If you get a wire(AKA antenna) that's resonant at that frequency, boom you've got a component that's throwing off a ton of RF hash.

The best thing you can do is buy name-brand products that have gone through proper RFI testing. Usually when you buy cheaper power supplies the first thing they skimp on is the filtering.

 

[crazyal]

If it's just AM/FM causing an issue then I would try a filter for the antenna. Maybe the RF isn't in the 12v power line so adding ferrite beads aren't working because that's not where the problem is. Should be about $10. Plus (I think someone else pointed it out) you can always add a capacitor from the power lead to ground. It'll look like a battery until charged to DC then it'll have no effect where as AC will pass through it.

 

[vvanders]

A filter at the antenna probably isn't going to help much, all modern radios have pretty strong passband filters either at the IF frequency or in the front-end if they're direct conversion. If you're picking up things it's because that frequency is present in your RF environment.

Filter capacitors are only going to help if they're on the power supply output rather than input and the sizing is pretty important. Any resonance needs to be tuned to the proper RC/LC circuit that can also pass the amount of current required.

Really the best option if you have RF problems is to use ferrite cores since they don't require a circuit connection or you can shield the whole component in an enclosure.

 

[Jack1940H]

I am not familar with RF issues relative to LED's. A tyical LED is driven with a DC voltage source. The diode usually will excite (emit light) at around 3vdc-4vdc and perform at peak outut at arround 5 - 18vdc. If the LED is powered by an AC source it will have a built in transformer driver circuit that converts the 120vac line source to 12vdc. This might be where the rf is being generated and if so I have no idea of how to suppress it.

 

[k0ua]

I am not familar with RF issues relative to LED's. A tyical LED is driven with a DC voltage source. The diode usually will excite (emit light) at around 3vdc-4vdc and perform at peak outut at arround 5 - 18vdc. If the LED is powered by an AC source it will have a built in transformer driver circuit that converts the 120vac line source to 12vdc. This might be where the rf is being generated and if so I have no idea of how to suppress it.

They don't have transformer base power supplies. They use switching power supplies. Hence the problems with RFI generation. All of my Cree bulbs seem to be RFI free. At least from any that I can find in hunting from around 300 khz to over 50Mhz. The Cree bulbs have went thru several iterations and changes in design in a short time. and I haven't needed to buy any lately, so I can't swear that they haven't cheapened the design, but all I have (3 separate designs) are clean.

 

[supertaster]

Does anyone have an answer to this? Supertaster, did you figure out a solution to your radio interference? I just recently installed 4" LED's on the front and rear of my tractor and also ended up with radio interference. I have found quite a bit of people saying they have the same issue but have not found any definite solutions. Sounds like the ferrite cores work for some and not for others.

Hi. No I didn't get anywhere. I will be active on it again now that plow season is on again. I couldn't decide what to order to try out and just put the issue on the back burner.

 

[k0ua]

Hi. No I didn't get anywhere. I will be active on it again now that plow season is on again. I couldn't decide what to order to try out and just put the issue on the back burner.

Try putting some .1 microfarad disc ceramic capacitors at least a 200 volt volt rating across the power leads of your 12 volt LED lights right up close to the lights, or if you can open the housing and put it back together again right where the power lead come in. These capacitors are not polarity sensitive. Before you solder them in, you can touch them across the 12 volt + and - leads and see if they help. They should make a big difference.

 

[k0ua]

Engineers that cut corners, and engineer products that create RF energy that are not supposed to radiate anything but light, when during the design process these problems can be easily mitigated by proper application of bypass capacitors and inline choke filters just to save a few cents per unit should be taken out and horsewhipped.

These problems have reared their ugly heads because our regulatory agency's have in no way enforced the standards that were set long ago for incidental unintentional RF radiation. The invention and rise of the switching powers supply to supplant linear transformer based supplies in the last few decades to produce cheap lightweight and compact power supplies have become the norm.

Switching power supplies have totally taken over now, and most devices in my home have switching power supplies, and I have spent many hours and much money solving the problems they cause to radio reception. Most people don't know or care that their "chargers" and power supplies emit RF energy, but I do.

But to have a simple 12 volt LED light bar produce enough RFI to affect the Mobile broadcast receiver in a tractor is disgusting and totally uncalled for and unnecessary and would be easy to mitigate at the design level. It is much more difficult to "retrofit" anything than it is to design it correctly in the first place.

 

[supertaster]

Try putting some .1 microfarad disc ceramic capacitors at least a 200 volt volt rating across the power leads of your 12 volt LED lights right up close to the lights, or if you can open the housing and put it back together again right where the power lead come in. These capacitors are not polarity sensitive. Before you solder them in, you can touch them across the 12 volt + and - leads and see if they help. They should make a big difference.

Hey, thanks for the information and education. It certainly seems to be a shift in economics and non-existent repercussions that has driven the corporations to belittle the role of quality control and end-user experience.

After the New Year I will look to attack the problem again.

 

[k0ua]

Hey, thanks for the information and education. It certainly seems to be a shift in economics and non-existent repercussions that has driven the corporations to belittle the role of quality control and end-user experience.

After the New Year I will look to attack the problem again.

let me know if you need help. I wouldn't mind helping you over the phone if you need it. I have over 50 years of electronics experience. I will help you if I can.

 

[supertaster]

Thank you. That is a very generous offer. Happy New Year!

 

[Fallon]

Engineers that cut corners, and engineer products that create RF energy that are not supposed to radiate anything but light, when during the design process these problems can be easily mitigated by proper application of bypass capacitors and inline choke filters just to save a few cents per unit should be taken out and horsewhipped.

These problems have reared their ugly heads because our regulatory agency's have in no way enforced the standards that were set long ago for incidental unintentional RF radiation. The invention and rise of the switching powers supply to supplant linear transformer based supplies in the last few decades to produce cheap lightweight and compact power supplies have become the norm.

Switching power supplies have totally taken over now, and most devices in my home have switching power supplies, and I have spent many hours and much money solving the problems they cause to radio reception. Most people don't know or care that their "chargers" and power supplies emit RF energy, but I do.

But to have a simple 12 volt LED light bar produce enough RFI to affect the Mobile broadcast receiver in a tractor is disgusting and totally uncalled for and unnecessary and would be easy to mitigate at the design level. It is much more difficult to "retrofit" anything than it is to design it correctly in the first place.

Lol, I never noticed your handle before, always assumed it was Kubota or Kioti related. Callsign I'm assuming? N7HKR myself, bagged by exra this year.

 

[k0ua]

Lol, I never noticed your handle before, always assumed it was Kubota or Kioti related. Callsign I'm assuming? N7HKR myself, bagged by exra this year.

I never knew you were "one of us", Yep, I have been KØUA since 1975. Congratulations on getting your Extra.

 

[David_Kb7uns]

Interesting note, while we are talking LED lights, was on the Geochron site the other day dreaming about their highly priced wall clocks and they have upgraded and can upgrade all the old models to LED lighting. But there is one model still made for Amateur Radio use and it is using the old tube fluorescent system, and no mention of CFLs as they would probably match the LEDs for QRM.

David