Noise on AM band only, Also CB radio noise. - JeepForum.com
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post #1 of 17 Old 05-05-2014, 12:55 PM Thread Starter
BadKarma1701
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Noise on AM band only, Also CB radio noise.

THE RADIO
I have a strange issue.. when I have my radio on the FM band there is no problems, When I switch to AM I get static that rises and lowers even at a stand still. I also get what I assume is alternator noise as I speed up. However it is only in AM mode. I only listen to the AM after 10 PM... Coast to Coast AM spooky and weird stuff. lol...... If it matters and most of my way home has above power lines and I have one of those short rubber like antenas.


THE CB RADIO
I have a Uniden Radio with a Four foot adjustable firestick antenna on a spring, firestick amtenna mount to tub and paint has been removed at grounding point for max grounding. It Is wired straight to the battery both power and ground. When I turn the radio on there is the normal radio static. However when I start the Jeep the noise levels of static jumps and I also get some noise as I sped up or slow down.
Any deas and fix's ???????


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post #2 of 17 Old 05-05-2014, 03:56 PM
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Make sure all the grounds are good. Sounds like you have a bad ground somewhere. They sell noise filters that you can put in line to help hide that. Could be your alternator also bleeding through the system.
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post #3 of 17 Old 05-05-2014, 06:27 PM
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Some radios pick up more vehicle generated static, and some pick up less. Some vehicles make more static, and some make less. Cheaper radios usually omit noise reduction circuitry to reduce the price of the radio.

Are you using resistor spark plugs, and resistor plug wires ? Are all the tune-up parts fresh, including the coil ? Are they top quality brand name parts ?

As suggested, make sure all the ground connections are clean and firmly attached. Look into some 12 volt power line filters. Use the Google to find more CB radio and Ham radio info on identifying and curing radio noise, adding capacitors at the fuel pump and at other noisy electrical components may help.

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post #4 of 17 Old 05-05-2014, 08:34 PM
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Originally Posted by BadKarma1701 View Post
THE RADIO
I have a strange issue.. when I have my radio on the FM band there is no problems, When I switch to AM I get static that rises and lowers even at a stand still. I also get what I assume is alternator noise as I speed up. However it is only in AM mode. I only listen to the AM after 10 PM... Coast to Coast AM spooky and weird stuff. lol...... If it matters and most of my way home has above power lines and I have one of those short rubber like antenas.

All noise generated in nature, and by electrical devices in vehicles, is broad band impulse noise and readily picked up by AM receivers. Broadcast band and CB are AM receivers. FM receivers are, by their nature, not sensitive to impulse noise if they are properly designed. Additionally, the spectrum of impulse noise is affected by the length of the radiating element which tends to affect the level of noise to varying degree by frequency. This tends to concentrate noise radiation at the lower frequencies.

Your problem with the AM radio is exacerbated by the use of an inadequate antenna. The antenna is close to the noise source and not efficient at the broadcast band so it gives preference to the noise. The noise level overwhelms the desired signal. A better antenna would help, but likely not eliminate the noise. Nothing will help when driving under high tension power lines. Some lines are more inefficient than others and higher voltage lines will have more noise.

Your interference is probably spark related and reverting to stock plugs and wires would help, or even eliminate the issue at no loss of engine performance.

Alternators do cause RF interference occasionally. Diodes are switches and turn on and off rapidly, and although there are no sparks (hopefully) do generate RF as well as audio noise. Field excitation, if done by brushes and slip ring, will also cause trouble. This noise is only effectively removed at the source. Noise blankers and limiters are poorly under stood by most and are not responsible for your CB or broadcast band issues.

That rubber ducky is not helping.

Phil
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post #5 of 17 Old 05-07-2014, 09:55 PM
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The newer and more electronic the vehicle it is the more noise. Both radios you are running are having noise on the AM freqs which is normal. On the CB you can squelch it out. The biggest thing for the CB is to run power and ground directly to the battery. Make sure ALL motor and electrical grounds are hooked up and upgrade them if need be. Believe it or not you may just have to also add a ground to your exhaust pipe. Us HAMS all do it for the HF freqs.
Short rubber ducky antennas are horrible for CB's. They have limited range to begin with. You need to create a proper ground plane for your antenna and want it as high up as possible. I run an ugly stick on my roof as close to center as possible. The best CB antennas are actually the really big steel whips. They are great when sitting still but deflect like crazy when moving. That's why I run an adjustable ugly stick or K40.
Not only will you get noise from powerlines but you will get noise from lightning strikes in the distance. I can actually judge storm distances from the noise level from the strikes.
Pick up a HAM radio book on antennas. You will learn a lot on making the CB work better.
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post #6 of 17 Old 12-31-2016, 02:30 PM
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Looking for part number and/or link

Sorry to resurrect ancient thread, but my 2002 Jeep Grand Cherokee Overland has same issue. AM radio worked perfectly before the dash had to come out to fix HVAC. I know the ancient lore about the antenna ground being no good once the dash removed. Already had ground lead run from base of antenna to negative battery terminal.

A generic in-line antenna noise suppressor will not work. Jeep used a custom sized antenna connection. Not enough room for 2 adapters AND a generic noise suppressor.

I am certain the interference is coming from the fan. Some previous owner had hacked the wiring on that before and it required quite a bit of repair. If shut the fan off 99% of interference goes away. Don't really want to go digging around for those wires and a place to hack in those old style condenser looking noise suppressors.

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post #7 of 17 Old 12-31-2016, 03:52 PM
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My first suspicion would be that a ground wire was left disconnected when you reinstalled the dash. Or could someone have installed non-resistor spark plugs? Normal spark plugs have internal resistors to eliminate spark noise, some aftermarket spark plugs don't have the required resistors and the spark plugs then generate a lot of static which will be heard over the AM car radio or CB radio.

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post #8 of 17 Old 12-31-2016, 08:00 PM
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Originally Posted by Jerry Bransford View Post
My first suspicion would be that a ground wire was left disconnected when you reinstalled the dash. Or could someone have installed non-resistor spark plugs? Normal spark plugs have internal resistors to eliminate spark noise, some aftermarket spark plugs don't have the required resistors and the spark plugs then generate a lot of static which will be heard over the AM car radio or CB radio.
I had mechanics do it, not me. Spark plugs were not changed and everything was fine before. Quite a bit of work needed to be done on the wiring for the fan _and_ when I shut the fan off I don't have interference/noise. Already put a ground wire on the antenna, but really am looking for a part number to an antenna radio noise suppressor which works with the custom/special Jeep connectors.
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post #9 of 17 Old 01-01-2017, 12:00 AM
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As an antenna guy I don't believe that antenna noise suppressor, whatever that is, is the fix. I don't believe the antenna is the problem at all. Those mechanics messed up the wiring in the instrument cluster somewhere.

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post #10 of 17 Old 01-01-2017, 10:33 AM
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Originally Posted by Jerry Bransford View Post
As an antenna guy I don't believe that antenna noise suppressor, whatever that is, is the fix. I don't believe the antenna is the problem at all. Those mechanics messed up the wiring in the instrument cluster somewhere.
I've been leaning to the idea of putting in a different antenna. I doubt those mechanics messed the wiring up per-se as I've done quite a bit of mechanic work myself. They did try to unscrew a royal mess under there and perhaps were not successful. Some previous owner had tried various "cheap hacks" like reversing the blower motor in a misguided attempt to blow the foam rubber out of the coils. Until one takes the dash out they cannot fully understand just how bad that advice is. I saved this Jeep from the auction and after sinking almost as much in repairs as I paid for it, have it very close to good. Will decide this summer about getting the paint touched up where it has scratches and nicks. (Odd there are no visible dings/dents though.)

http://www.interestingauthors.com/bl...not-cold-pt-2/

I know that VW has a notorious antenna problem with a rubber gasket that breaks down removing all shielding. Unknown if there is a similar problem on the 2002 Jeep Grand Cherokee Overland.

Antenna filters tend to have standard connectors and Cryco couldn't stoop to using a "standard" connector.
http://www.frys.com/product/6567473

Some of them get bundled in with signal boosters which wouldn't be a horrible thing since I live remote, but, my real problem is on AM not FM.
http://www.sears.com/unique-bargains...&blockType=G11

RockAuto claims to have the factory antenna for $14 . . . but . . . it doesn't say if it is a complete replacement including base and cable. That price makes it sound like just a mast.

I have found many posts in many places which claim any time the dash comes out of one of these the grounding for the antenna gets damaged. Adding a ground lead helped immensely but didn't fix the problem. The _only_ car stereo shop in the area shut down in November. They used to do decent work, but after 30 years the guy chucked it in.

Is the antenna cable clipped/anchored anywhere or can I use the poor man's trick of 30 lb. test fishing line tied to the end and gentle pulling? I haven't found an aftermarket antenna which is the same height as the factory stick.

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post #11 of 17 Old 01-01-2017, 12:09 PM
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Let me be a little more firm... your antenna is not the cause of the noise you're hearing in your AM radio. Keep in mind your FM radio works fine with the same antenna. AM radios are far more susceptible to generated noise/static like you're hearing, it's the nature of the differences between AM and FM. You're barking up the wrong tree by clinging to the idea that replacing the antenna or installing some kind of voodoo antenna noise filter is going to help. Been involved with this stuff for over 50 years.

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post #12 of 17 Old 01-01-2017, 01:32 PM
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Originally Posted by Jerry Bransford View Post
Let me be a little more firm... your antenna is not the cause of the noise you're hearing in your AM radio. Keep in mind your FM radio works fine with the same antenna. AM radios are far more susceptible to generated noise/static like you're hearing, it's the nature of the differences between AM and FM. You're barking up the wrong tree by clinging to the idea that replacing the antenna or installing some kind of voodoo antenna noise filter is going to help. Been involved with this stuff for over 50 years.
I hear what you are saying. I would not say the FM works "fine" it also has issues, just not by comparison. Adding a ground lead to the antenna caused AM to go from pure static to tolerable static on strong AM stations and still inhumane on weaker band like 580 AM which is one of the NPR stations around here.

I live quite rural and have had many old Jeeps. There is _always_ something wrong with the wiring. My 1990 Wagoneer Ltd came with a factory Mopar noise suppression block wired into the incoming power. Without it the factory radio was useless and the aftermarket I put in to get a CD player barely survived 3 years.

http://www.interestingauthors.com/bl...-a-jeep-thing/

The source of the interference is the blower motor and its wiring. When the blower motor is completely off there is little in the way of discernible static or interference. Of course the blower wasn't really functioning prior to the HVAC removal and replacement.

I have used a good number of signal booster/noise filter products out here because we are so far out and now have all of the signal interference from those ugly windmills. When the windmills are being turned AM 580 is nothing but a high pitched digital data signal on any radio I own in the house, office, or vehicle. My first experience with auto am/fm (mostly fm) signal boosters came during the dark days of KRACO stereos which later became known as KMC (K-Mart Company) brand. Friend opted for Realistics (Radio Shack) which had similar reception issues. We were poor and Pioneer had yet to come out with their first Super Tuner deck. Most of the FM signal boosters I used were various Wineguard products which came with on/off switches because they were kind of mindless in how they boosted.

http://www.winegarddirect.com/viewit...(BF8809)&post=

Newer style ones do not use an on/off switch. They have a wee bit of signal meter logic only boosting signals below a certain level but they are bulkier and much more expensive.

Hooking a ground to the antenna made a marked improvement, but one needs to understand what that phrase means. The underside of the antenna looked corroded. It was cleaned a bit and a hose clamp holds the naked copper wire against it. The retaining nut for the antenna was barely removable because it too seemed to have been road salted into place. Quite a bit of panther pee and a big set of pliers to hang onto the base plus time for the pee to soak in was required to make it budge. A new antenna is in the future because this one has seen too much salt. Oddly enough there is no visible salt damage inside of the fender or to the body.

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post #13 of 17 Old 01-01-2017, 02:17 PM
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Ok you're the apparent expert here by having rejected the advice you asked for. Go for whatever you want to do.

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post #14 of 17 Old 01-01-2017, 02:58 PM
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Ok you're the apparent expert here by having rejected the advice you asked for. Go for whatever you want to do.
LOL,

Not the expert, just someone who has been down this road where I live and the existing antenna probably doesn't have long for this world. A proper noise filter would prove that out but the salt rot was rather convincing.

Thanks for contributing though.

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post #15 of 17 Old 01-02-2017, 09:45 AM
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Originally Posted by seasoned_geek View Post
..... AM radio worked perfectly before the dash had to come out to fix HVAC. ... I am certain the interference is coming from the fan. .... If I shut the fan off 99% of interference goes away.
Fix the wiring issues, and that should fix the noise issues.
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