interference coming from my truck

[Mikado]

I have discovered that my Honda Ridgeline emits RF interference / static on 147.76 MHz. This occurs when the key is in the first click (engine off) and without any other accessories turned on. I have a handheld Wouxun KG-UV6D. I am receiving the interference with both the stock antenna, and a magnetic Hustler MX-270 roof antenna. I am also picking it up on my Uniden BC246T scanner. I have explored another forum for Ridgeline owners. There is a ham on that forum who reported the same problem, but I didn't see a solution. I am using the battery for the Wouxun, and I'm not drawing power from the truck's outlet. So I'm not getting interference through a power cable.

I have spent some time Googling interference, and reading about filters, ferrites, and more. Would any of those be useful in reducing / eliminating interference at this frequency? In the near future I may want to buy a real mobile radio. Since that would have a power cable, there would be a place to snap on some ferrite beads. But I don't know if that would help.

I am new to the hobby, so I'm still reading and learning. This frequency happens to be used by the local severe weather net. I also took the weather spotter class from the National Weather Service. So I'd really like to find a solution if possible. I appreciate any suggestions.

 

[popnokick]

Do you have any 12V to USB converters / cellphone chargers connected to any of the 12V sockets in the truck? Some models of those converters use switching power supplies that put out a lot of RFI. I find it's even worse when the cellphone / tablet is actually connected and charging. Sounds like normal background static.... or a steady carrier... and turning up the squelch doesn't help.

 

[mmckenna]

If you are picking up the interference on a handheld with an external antenna, the RFI is being radiated by something in the truck. Installing ferrite on the power leads for the mobile likely isn't going to fix the issue. What you need to do is find out where the RFI is coming from and fix that.

This might be a bit tricky to do. Some options would be to remove the antenna from your hand held and see if you still receive the noise. If not, you can move the radio around and see if you can pinpoint the source.
The other option might be to start pulling fuses, one at a time. When the RFI stops, you'll find your source.

Of course finding the source is only half the battle. Fixing the noise might be harder. Once you find the source, it's going to take some work to eliminate the noise. The way to do this will vary depending on the source.

You might even try contacting Honda and see if they have any info on this.

 

[kayn1n32008]

Wirelessly posted (Mozilla/5.0 (BlackBerry; U; BlackBerry 9900; en-US) AppleWebKit/534.11+ (KHTML, like Gecko) Version/7.1.0.746 Mobile Safari/534.11+)

Does your truck have HID lights? A local guy had some cheap china HID ballasts that created a racket on VHF. Solution was to remove them

 

[Mikado]

popnokick: Good suggestion! I do keep a charger plugged in at all time. I pulled it out, but that wasn't the source of the interference.

mmckenna: There are a few "dead spots" inside the truck. If I wave the radio around, the interference stops in certain locations. I did try removing the antenna as you suggested, and waved the radio all over the console and other areas. I did not get any signals without the antenna. I have more time tomorrow afternoon, so I'll try pulling fuses as you suggested.

kayn1n32008: I'm not familiar with HID lights. Are those headlights? I don't have them on at the time I'm getting interference. The only lights on inside are the dash lights behind the speedometer which are always on.

Thank you!

 

[AK9R]

HID = High Intensity Discharge

A type of lamp that has two electrodes positioned in a bulb that's usually filled with an gas and a metallic salt. The gas promotes initiation of an arc between the electrodes and the metallic salts vaporize in the heat of the arc to produce a very bright, usually very white, light. The electrodes are fed with an electronic circuit that typically uses a switching power supply to generate the high voltage required for the arc. That switching power supply may radiate RF energy unless steps are taken to reduce it.

 

[mmckenna]

The HID lights he's talking about are the aftermarket ones. If you purchased your truck new and didn't modify the headlights, then you are probably safe.

So, you need to use your radio like a probe, maybe even use a smaller antenna, or a short piece of coaxial cable with a small length of the center conductor exposed. This "sniffer" probe can be poked around to try to pin point the source. Of course it could be radiated by the trucks wiring, so that may be a difficult task. Pulling fuses might be your best choice at this point. Once you narrow down the source, figuring out how to fix it will be a challenge.

 

[majoco]

Computer(s)? Usually inside the cab somewhere warm and hopefully dry. A soon as you turn the ignition on it will be analysing temperatures inside and out, monitoring fuel pressure, waiting for you to turn the key to start so that it can open the injectors etc. Not usually in a metal box, just a plastic enclosure to keep the dust out.

 

[Mikado]

I think I found the source. I started pulling fuses one at a time as mmckenna suggested. The interference stopped when I pulled the fuse for the radio. I popped in in an out a few times to confirm.

So finding the source is only the first step. I'm not sure if anything can be done to resolve the problem. Has anyone else ever had a vehicle where the built in radio caused interference?

 

[mmckenna]

I've never had a vehicle with that issue, but it's not unheard of. Since the radios do a lot more than just music, it's not surprising.

You could start looking at the radio and try some ferrites around the wiring harnesses leaving the back of the radio. Don't forget the broadcast antenna lead. If that doesn't fix it, take a look at the radio itself, if it's not in a metal enclosure, one thing you could do is start wrapping foil around it to see if that helps. I've got some 2 inch wide adhesive backed foil tape that is great for this kind of stuff. The local hardware store had it in their plumbing department. It was for ventilation ducts. I've used it before to wrap around cables to make an easy shield.

Don't rule out the idea that the circuit that feeds the radio power doesn't power other things also. Not sure about Hondas, but my Fords have a lot of fuses in them, seems like they separate things pretty well. Some of my older vehicles had fuses that would feed multiple systems. While the fuse might be labeled "radio" it could feed other items. Satellite radio antennas, power antenna, separate amplifier, etc. Might take some studying of the wiring schematic to make sure you got it all. Likely it's the radio itself.