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RF noise from car
http://www.interceptradio.com/bbs/viewtopic.php?f=1&t=7697		 Page 1 of 1
Author:  gregz [ Thu Aug 07, 2014 12:30 pm ]
Post subject:  RF noise from car
I have a very RF noisy car.
it's a 2000 Honda Odyssey.
How do I quiet it down?

it transmits spikes all across the RF spectrum from 50Mhz to 450Mhz. It spits out noise that is 20dBm above the noise floor. The interference is in the shape of 200KHz wide spikes about every 1.5MHz all across (seamlessly!) the spectrum. And for fun all the spikes SWEEP down the spectrum at a rate of about 1MHz every second.

So if you are listening to something, it will go quiet for a second as it get's fully blanket by the dead carrier of the car, and then it comes back as the spike moves down the frequency, only to be fully blanketed again with in about 2 seconds by the next spike crawling down the frequencies.

This happens at all RPMs when the car is running. AND 15 seconds after the car is turned off. So I'm guessing it's the ECU.
How do I quiet this car down?

3 files is the maximum attachable below,
So here's a sample of:
320-380MHz
140-160MHz
108-140MHz

Attachments:
320 car on.JPG
320 car on.JPG [ 116.68 KiB | Viewed 2110 times ]
140 car on.JPG
140 car on.JPG [ 138.94 KiB | Viewed 2110 times ]
110 car on.JPG
110 car on.JPG [ 112.31 KiB | Viewed 2110 times ]
Author:  Jim [ Thu Aug 07, 2014 12:56 pm ]
Post subject:  Re: RF noise from car
Are you running your scanner on the car 12 volt system?

Does it still occur if you run a portable not hooked to this system?

From the samples it looks like it would happen on a portable also.

Do you have any other items in the car that run off the 12 volt system?

Does it occur with the ignition switched on and the car not running?

Sounds like the ECU is probably the cause.

Found this by googling.

http://www.amalgamate2000.com/radio-hob ... erence.htm

Good luck and let us know what you find out.
Author:  nickcarr [ Thu Aug 07, 2014 3:09 pm ]
Post subject:  Re: RF noise from car
I would check for a loose ground connection. They can wear out and fall off after 5+ years or so. I had to replace mine in the Durango. I literally just touched one with the tiniest of force and it broke (at the end.) It's good idea if you're doing any radio work.

ECU sounds like a good idea but there should be a SPG connection which the ECU should be apart of...

I would also check the Ignition coil packs. These are common causes of RFI when they go bad. Stick with OEM replacements and not aftermarket -- as they could be much worse.

Sweep a portable scanner or shortwave radio across the ignition coils and see if you can isolate the exact location.

http://www.autopartswarehouse.com/searc ... eplacement
Author:  gregz [ Thu Aug 07, 2014 3:15 pm ]
Post subject:  Re: RF noise from car
I'm not running the scanner off of car power.
The scanner is on a stand alone cart outside the vehicle using the city grid.

I do have a couple other things that run of 12V Accessory but they were all unplugged, or at least turned off if it's installed in the dash.

Yes it does occurs with the ignition switched on and the car not running. And even for 15 seconds after you take the key out, lock the car and walk away.

That URL is .. well scary. that's a 1979 Honda Accord. My car is 30 years more modern. If Mike had to use 10 feet of strap, I will have to use 100 feet. I'm kinda not looking forward to wrapping every cable in aluminium foil. This is my 1st car with a real ECU, power windows, and fuel injection.. perhaps this amount of noise is "normal"?
Author:  nickcarr [ Thu Aug 07, 2014 3:29 pm ]
Post subject:  Re: RF noise from car
gregz wrote:
This is my 1st car with a real ECU, power windows, and fuel injection.. perhaps this amount of noise is "normal"?


Umm no... it's not normal.

RFI is possible from everything from electronics, lack of grounds, ignition coils, alternator, ECU (improper grounding), fuel pumps and lights.
Author:  mrk [ Thu Aug 07, 2014 9:03 pm ]
Post subject:  Re: RF noise from car
About that ground...make sure your hood is grounded too! I had a old 79 Buick that I started my radio hobby with. I too had some pretty violent RF noise from it. I even took it to a auto electric repair shop who didn't know what to do.

I then saw another car of a friend and noticed that it had a ground wire running from the firewall to the hood. I replicated this and immediately the noise dropped out.

-K
Author:  TechnoWeenie [ Thu Aug 21, 2014 10:27 pm ]
Post subject:  Re: RF noise from car
Buy a mechanical IDI diesel ;)
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