cant find the answer

[metalcd]

morning, my name is chris, and i have interference issues. its not the normal everything coming into my cb, its my cb going into my car stereo. i drive an 08 rubicon, my stereo is a pioneer avic f-900bt (nav unit) my cb is a cobra 75wxt, and a 4ft firestick antenna mounted to the tail gate. cb power wire is to the battery, ground is to the metal dash frame, coax runs under jeep along the frame. when jeep is powered off, no problems with anything. when jeep is powered on and nav unit comes on and i attempt to transmit it goes strait to my stereo speakers. i have turned the stereo off but the nav unit still stays on and it still interferes. any ideas.

by the way, i have been looking at the forum for answers by searching and general browsing.

thanks for any input that you all can offer.

[231]

Ah, another Jeeper...welcome to the forum.

Well, the first thing I'd ask is where did you locate the radio box, and what is your standing wave (aka "SWR")? Frankly, I don't ever recall hearing anyone getting into speakers with a Cobra 75. It's audio is usually so low maybe they just didn't hear it? Anyway, not important.

I'd have other ideas, too but the answers to the above might help some. The most common problem I've heard guys run into with getting into anything (i.e. speakers, dash display, etc.) on their Jeeps is a bad standing wave (believe it or not). Mounted on the tail gate tells me alot...especially if you've not tuned your antenna. Most of the time guys have a hard time achieving a good counterpoise on the tailgate because they are reluctant to drill any holes let alone run added grounding straps.

Not sure if that helps, but the first things that come to mind.

[metalcd]

dont have a swr meeter, so cannot tell you what it is. the box is under the driver side dash, also attached to the metal dash frame. the antenna is attached to a teraflex mount that bolts into the stock tire carrier mounts. i can add straps its not a big deal, i already have the coax back there.

[231]

dont have a swr meeter, so cannot tell you what it is. the box is under the driver side dash, also attached to the metal dash frame. the antenna is attached to a teraflex mount that bolts into the stock tire carrier mounts. i can add straps its not a big deal, i already have the coax back there.

Well, I'd lay a dollar to doughnuts that your standing wave is off the scale. I'm guessing it's this is the mount you have?



And a stud assembly probably similar to this?



If so, between the paint on the bracket (both underneath where the connector grounds, and where it bolts to the tailgate) you simply aren't getting good enough contact. I would probably do one of two things;

1.) Scrape the paint off the bottom portion of the mount where the grounding portion of the stud assembly meets. At this point I'd do a decent lug connection that will take a decent sized wire or braid and run it to a separate shiney metal point on either the chassis and/or tub (or both)

OR

2.) Drill a second hole pulling the above connection to a common ground point (I'd probably use a self tapping screw after a pilot hole) and run a ground wire or strap again to shiney metal point on the chassis and/or tub (or both). Either way, you'll need to get a good shiney metal to metal contact on the bottom of the mount where the stud assembly meets the mount.

You really will need to set the standing wave on that antenna. The Firestiks are very narrow banded and touchy to tune. In fact I would probably do that before I did anything else. I could be wrong, and if I am all you'll need to do is tune the antenna. If you can't tune it, it's a sure bet the grounding issue is the culprit. Assuming of course your insulator is installed correctly. Believe it or not, I've known guys running what you are for an antenna getting into their stereo that once the antenna was tuned, it disappeared. The worse thing that'll happen by doing all of this is your antenna will be working properly and you'll still be getting into your stereo. But I have a feeling you'll see big improvement.

Any friends you know with a meter and jumper cable? If not, they aren't all that expensive. Check out some of our sponsors on the bottom of every page, most all of them carry them.

Hope that helps a little.

[metalcd]

bought and installed grounding straps. put bolt directly to mounting bolt then to chassis bumper mounting bolt.
bought swr meeter, first test swr was at about 1.5. after tuning i was able to get it down to 1.1.
i am putting out 3w of power.
i still have the issue.

[231]

bought and installed grounding straps. put bolt directly to mounting bolt then to chassis bumper mounting bolt.
bought swr meeter, first test swr was at about 1.5. after tuning i was able to get it down to 1.1.
i am putting out 3w of power.
i still have the issue.

Awesome! Sounds like that's out of the way so obviously it can be eliminated. From here there are several things you can try not in any particular order either, but starting with the things that don't cost anything would be a good move.

Just out of curiosity, have you by chance given a quick call to your dealership to see if perhaps the factory has had similar issues? If I recall the electronics are suppose to be able to receive reasonable amounts of RF without a problem. Your radio can't be really modified much, no amp, basically a stock set up and less than legal wattage with probably 60% modulation (or less). I'm wondering if the factory isn't already aware of inadequate shielding? Just a thought...might be worth a few calls and searches. It could be they have some shielding device they hand out or install if it's a known problem.

I'd probably start by moving the radio connection box to a different location...if only temporarily to see if it helps, along with running a separate ground wire back to the battery so you have a +/- pair to eliminate any possible ground loop. Next I'd invest in some snap on ferrite beads...the good 30 mix ones from DX Engineering would be my first choice, but there are some others that sell cheaper ones that should work too.

If none of these things make any difference at all, I'd consider trying a different piece of coax run inside the tub for testing. As I try and picture your coax run under the JK, it's probably brought up through a rubber grommet that is in the firewall? I know on YJ's and TJ's it's there. If so that grommet on the TJ and YJ is very close to the main wiring harness, and it might be on yours also. On the off chance you have some CMC taking place, I'd probably make sure they aren't in proximity of each other...in other words, take a look around everywhere the coax is run and see what's in proximity. It could be something as simple as them not touching or moving further apart solves it?

I'm sure there are more things that can be tried, but before you go making anything permanent I'd probably suggest giving things a try first to see if they help. Too bad you aren't in my area as I have plenty of ferrite beads, coax, antenna, etc. etc. to try. I would have guessed the making sure the antenna was tuned was the ticket because I've seen it be for others. But it looks like I was wrong and it's going to require more (which is a bummer). The antenna tuning should have been done anyway, and I'm sure you'll be glad you did that. Your radio will like you for it anyway.

Hope that helps some.

[hyson]

Curious. I have an 02 Liberty and have the same exact issue.

Uniden PC122XL radio, power plug is in cigarette lighter, antenna is POS Radio Shack magnetic mount on roof - no supplemental grounding.

My guess is that there's something wrong with the cb or the factory Jeep speakers aren't grounded correctly.

Freakin Chrysler products.....

[madsage]

Weird,

I have a TJ, I run about 600watts and does not mess with my AM/FM or an ICOM dualband VHF/UHF radio.
What kind of coax are you running? I use gray beldin 8x in my jeep. If you are running cheap RattShack RG58, this "might" be the problem?
Also my coax is ran on the inside of the jeep (under the carpets) to the back corner and exits where the rear lights go through the grommit. Also I run a 102 whip with the ball on back just above the driver turn signal light. Hope this helps. Its possible the new JK radios just pickup interferences as somebody else suggested.

I'm kind of leaning twords poor shielded coax however. You'll have to experiment. And if all fails replace the stock radio with a nice Alpine with satellite and usb mp3.

933 Arizona

['Doc]

It sounds like an over load problem, which is fairly common. It amounts to the stereo not being as shielded as it could be, or RF getting into it through some of the wiring. A five gallon bucket of those ferrite torroids would be very handy! Loop the various speaker, power, whatever other kind of cords/wires coming out of that stereo through those torroids.
- 'Doc

That five gallon bucket is sort of an exaggeration, but maybe not by a huge amount.

[ny221 8pill]

ya you are getting a little rf field in the cab of your jeep and the prob does sound like the radio itself is not shielded properly and is letting the rf signal penatrat the radios little internal amp and there you go.. you here your cb through your radio, prob not to much you can do now but change the fm radio out in your truck, but it sounds like thats not a option, sounds stupid and not sure if it will work, and never told someone to try it before but, pull radio out and try to wrap it the best you can in fine copper screen, to try to block the rf from penitrating your fm radios insides, copper screen blocks radio signals, just a dumb thought,,, ny 221 good luck

[ny221 8pill]

ya n forgot to add like the gentalmen before me, get those core ferrits and wrap any audio in wires plus power and ground wires leading into radio to, it will help..

[hyson]

My issue fixed itself.

I got a decent antenna, mount and coax. I mounted my 5' Wilson on a Firestik door jamb mount and used K40 coax. No more cb bleed into my radio/speaker system.