So i bought a really cheap used cb handheld to use as a sniffer and walked around my suburban with it. Sticking the antenna here and there trying to find the cause of my rfi woes. I found it, its comming from a wire harness under the back driver side fender. Its two wire looms that have the wires for all the rear tail lights etc, fuel pump i think, and some others to what i dont know, haven't investigated yet. Redid the ground under there, still rfi. Replaced the fuel pump, still rfi. I wonder what else it could be? The rfi seems to be radiating from the wires like an antenna. I was thinking for the hell of it, wrap the thing in foil tape to see what happens? Like an rf shield. Still waiting for dry warm weather so i can crawl under there and see where the wires go to. Any ideas? Something easy to try? I cant imagine the rear lights causing rfi
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I found where the mobile rfi is comming from
- Thread starter groundwire
- Start date
I am curious to see how it pans out. I ran my coax thru the taillight harness and didn’t have noise. Doubt it’s your taillight.
Did you try some ferrites? Mix 61 & 31
Although not exactly the same, my 12/120v NORCOLD portable refrigerator/freezer caused so much RFI that I couldn’t operate the radio while underway in the Pete when the compressor kicked on.
A huge toroid from PALOMAR ENGINEERS was the fix. I could still hear the noise (to tell you it was there), but it was no longer Interference worthy of the definition.
The radio wasnt ever powered by vehicle circuitry and the chest was a good six feet back and four feet down from the radio. Coax went sideways from the radio.
In different brand/model trucks since (sometimes with coax passing overhead by five feet), no change to noise reduction.
My big truck goes from quiet to loud depending on what is running. That’s the start. The chart. On a U980, I can track S-Units before daylight very easily.
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Yea its not the lights. Im dying to get under there and find out where all the wires go to so i can find the problem but its still rainy and cold up here. No garage either so kind of a bummer.
I was thinking about ferite beads as well but i would hate to spend the money and it doesn't work. Not enough slack in the wires to wind thru a torroid core
The fuel pump can be a major source of noise. The heater a/c blower and wiper motor too. The dc brush motors are noisy because of the commutator and it uses the vehicle wiring as the antenna. Shunting the rf to ground right at the motor would probably help. Something like a 0.01 micro farad ceramic disc capacitor across the wires in the plug would be a good start. Also grounding the radio to the body of the truck can pick up noise if a noisy device uses the same path in the body to the battery negative.
a good way to determine whether or not its the fuel pump is to have the radio on and the volume up and the key off.
now turn the key to the ON position which usually primes the fuel pump for a second, and you will hear the noise in your radio as this happens.
there is an article from years back where someone made up a harness all wound through torroids and then spliced it in right near his fuel pump and it made a big difference.
i think the vehicle was a ford in that case.
LC
now turn the key to the ON position which usually primes the fuel pump for a second, and you will hear the noise in your radio as this happens.
there is an article from years back where someone made up a harness all wound through torroids and then spliced it in right near his fuel pump and it made a big difference.
i think the vehicle was a ford in that case.
LC
May sound dumb..... but what did you wrap through the toroid? The power feed.... or the coax?????
It is the fuel pump. Did that test months ago and its a yes. Put a new fuel pump in, it got quieter but still there. Unfortunately i cant get to the fuel pump cause its in the gas tank and the plug and harness are in between the gas tank and body. No trap door, you have to drop the tank to get to anything fuel pump related.
The power gets there from the battery somehow. I’d try “something” (noise abatement) closest I could get as experiment.
The whole is radiating as an antenna. What might result in treating part of it?
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Am stuck now several days under a load waiting to be delivered.
Am at a favorite truck stop (Petro, Weatherford, TX), so it’s not as perturbing when this happens in West Timbuktu.
One can’t NOT think about radio performance when sitting still several days.
The question of noise with engine off, etc, is still affected by running the ESPAR diesel-fired bunk heater (almost imperceptible); the obvious gain when the THERMOKING APU fires up, and when running the main engine.
Second is daylight or dark.
Quietist is in the pre-dawn hours away from a metro area, everything turned off.
To run an experiment of noise treatment, this suggested background leaves no room for doubt.
I’ve had MIX 31 ferrites sprouting all over the rig. When I also seeded MIX 61 (thanks, M0GVZ) it was confirmation in the quiet hours at several different rest areas made me a believer (I’ll use 61 first in the future).
These two aren’t the only choices.
But being able to detect a star farting at 3.8k light-years distance DEFINES the ideal noise background whereby one knows he isn’t fooling himself.
This truck stop less than 20-miles west from the IH-820 Fort Worth loop. “Quieter” than my home about 2-miles from that loop despite big trucks parked around me (thankfully, no reefers; but some are idling all night).
Though where I am isn’t perfect, I could idle across this huge lot to a remote parking spot about o’dark thirty and come very close to a West Texas rest area (where the Milky Way obvious almost every night).
Throwing noise patches in every direction is SOP (have the priest bless them, right?), so I am recommending also a remote location to find satisfaction in testing.
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Am at a favorite truck stop (Petro, Weatherford, TX), so it’s not as perturbing when this happens in West Timbuktu.
One can’t NOT think about radio performance when sitting still several days.
The question of noise with engine off, etc, is still affected by running the ESPAR diesel-fired bunk heater (almost imperceptible); the obvious gain when the THERMOKING APU fires up, and when running the main engine.
Second is daylight or dark.
Quietist is in the pre-dawn hours away from a metro area, everything turned off.
To run an experiment of noise treatment, this suggested background leaves no room for doubt.
I’ve had MIX 31 ferrites sprouting all over the rig. When I also seeded MIX 61 (thanks, M0GVZ) it was confirmation in the quiet hours at several different rest areas made me a believer (I’ll use 61 first in the future).
These two aren’t the only choices.
But being able to detect a star farting at 3.8k light-years distance DEFINES the ideal noise background whereby one knows he isn’t fooling himself.
This truck stop less than 20-miles west from the IH-820 Fort Worth loop. “Quieter” than my home about 2-miles from that loop despite big trucks parked around me (thankfully, no reefers; but some are idling all night).
Though where I am isn’t perfect, I could idle across this huge lot to a remote parking spot about o’dark thirty and come very close to a West Texas rest area (where the Milky Way obvious almost every night).
Throwing noise patches in every direction is SOP (have the priest bless them, right?), so I am recommending also a remote location to find satisfaction in testing.
.
