CB Radio interference when driving

[Jamooche]

I installed my old Cobra 75 WX ST today on my Jeep. That CB has always worked perfectly in the past on my old truck. I installed it with a Firestik Jeep TJ hood channel mount. Everything was working perfectly with amazing reception until I started driving.

When I drive the truck it causes massive interference feedback noise and only goes away with the squelch turned up all the way, but then you can hear or transmit anything. The instant I come to a complete stop, it goes away. I tried everything...removed the power and ground wires from my Aux fuse block and wired directly to the battery, removed the antenna and had it taped to the passenger door, on the passenger seat, and even tried a different cable and mount. I had the control box initially under the glove box and then later tried to get it work sitting on the passenger seat. All locations worked well until I started driving. The brake pedal would also sometimes interfere...when I tapped the pedal it would cause static on the radio.

Does anyone have this feedback problem? I'm going to try mounting it to the spare tire carrier tomorrow to see if moving it further from the engine bay helps. Would a different model CB help?

Thanks for any help on this!

[Jamooche]

It also interferes with the Mygig head unit when set on the Aux input mode. When I key the mic, it makes a click sound over the stereo.

[JackMac4]

Sounds like a ground issue to me - have you checked all your ground points, including pin #1 on your cb input?

[Flukinuki]

Could be a ground problem as stated. It may also be alternator whine since you said the interferance increases with vehicle speed. Not sure how the brake pedal figures into the equation. If its alternator whine you probably have some on your transmitted signal as well. If you have a friend with a cb that you can chat with, I'd suggest having him follow you for a short ride while chatting. Ask him/her if they can hear the whine. You could probably even do it in the driveway and rev the engine a little while talking. As th RPM's go up so would the interferance. Radio Shack used to sell small cheap filters to clean up the power going into the radio and eliminate the problem. Hope it helps.

[Jamooche]

Thanks. I'm going to try some heavier gauge wire for the grounds. Reving the engine when stopped doesn't cause interference at all, only when I am moving at any speeds greater than 1-2 mph.

I may buy a new cb today at radio shack and see if it's something wrong with my cb.

[JackMac4]

You get it fixed?

[Jamooche]

You get it fixed?

Thanks for asking. No, it's not working properly. I increased the wire lengths so that it was all running from the trunk with the antenna on the tire carrier...no change. I bought a new CB from radio shack and that does the same thing. There was a tiny improvement when I moved the ground to a better location though. I still haven't tried better quality higher gauge wire. (I need to go to the store, I'm all out.) I've tried 2 antennas, 2 mounts, 2 coax wires.

I'm going to buy some radio noise filters. One is for the antenna coax and the other is for the power and ground wires. I guess I can't post the links because they are not sponsors, but one piece is called the Noise Chopper and the other is NF20. You can get them at Radio Pro Shop .com and then scroll down to noise filters.

I found an article on the web about a Jeep TJ that had to ground the muffler to stop the interference, but I have a friend with a TJ who has done nothing special. My friend who has the same radio as me had to change his spark plugs on his Land Rover Discovery, but I did nothing special when I had mine. I've also noticed that this topic is so diverse and problematic that whole books have been written on the subject.

Here's some shots of the Firestik Jeep TJ Hooch Channel mount:

http://www.pbase.com/jamooche/firestik_tj_cb_mount

[Flukinuki]

I looked at the filters your considering. The NF 20 looks good to me but I'm not crazy about the noise chopper thingie. You really shouldn't have to use a filter on the coax side. To be honest you really shouldn't need a filter on the power leads either. Keep in mind that when you add one of these "filters" you're doing just that, filtering the noise, your not fixing the problem.

Question: have you tried doing a quick setup of your radio in a different vehicle? just open the hood and connect direct to the battery and a quick antenna mount? Might be something to try to eliminate the radio for sure.

To me it really sounds like there is something in your vehicle that is radiating the interference. Your right, theres been books written on the subject. Its going to be a matter of trial and error, but it really does sound like some form of ignition noise. The source could be ANY part of the ignition system (I'm not sure how the exhaust figured into your friends problem). If your connections are good then I would start looking for the source. It may be somethig thats going to cause a different problem down the road.

[Flukinuki]

It also interferes with the Mygig head unit when set on the Aux input mode. When I key the mic, it makes a click sound over the stereo.


This kinda makes me think theres a bad ground somewhere other than in your radio circuit.

[Jamooche]

This kinda makes me think theres a bad ground somewhere other than in your radio circuit.

Not only does it click when set on aux input, but if I turn the volume up a bit, it's like a PA system...I can hear my talking on the stereo speakers. It did this for my CB and the newly bought Radio Shack one.

As for my CB, I pulled it out of my old vehicle about a month before trying to install it in the JK and it worked perfectly. I also have 2 of the Cobra 75 wiring harnesses (sliver box that all the wires go into) and they both do the same thing.

[Flukinuki]

Check your PM's.

[1talljker]

There could be any number of causes, but the most common, and easiest to fix is the alterator whine.

I doubt that you are picking it up through the antenna, its much more likely that you are picking it up from your power leads. If you've connected straight to the battery, which is the recommended option, then you have a good ground. Check Radio Shack, or any of the online electronic component suppliers for ferrite beads.

Loop your power leads through the ferrite beads 2 or 3 times. What this does is act filter the unwanted frequencies out of your radio.

Yes it really is a fix, even power leads act as small antennas, and that's basically what's happening when you pick up alternator whine. Alternators give off a small amount of RF (Radio Frequency) noise, in fact all electric/electronic devices do. Your power leads are acting as an antenna and picking up the RF from the alternator. So the ferrite beads or filters are filtering out those frequencies given off by the alternator or other components.

Wrapping the coax 2 or 3 times through ferrite beads will have the same effect on the actual antenna signal, and should help clear up the interference with your myGIG.

Check this link (http://www.ac6v.com/techref.htm#RFI) for more in depth information. Its geared more toward Hams, but the principles are no diferent for CBs

[Jamooche]

Thanks 1talljker and Flukinuki. I bought those noise cancelling devices I posted about. I'm going to try those first. If they don't work I'll try them with what you suggested.

I'm starting to wonder if there'e something wrong with my Mygig unit or if when the dealer installed it, they did something wrong. I bought some new heavier 14 gauge wire today and will try installing the CB with that directly to the battery.

[07JKRUBI]

I am having the same problem.:thinking: I used 10 awg for the power and 8 awg for the ground. I ran both wires through the passanger side or the fire wall and directly to the battery and used the screw inside the fire wall as shown in the CB insall write up as a ground. I will be interested to see what you do to fix this as I have had no success.:D

[Jamooche]

I am having the same problem.:thinking: I used 10 awg for the power and 8 awg for the ground. I ran both wires through the passanger side or the fire wall and directly to the battery and used the screw inside the fire wall as shown in the CB insall write up as a ground. I will be interested to see what you do to fix this as I have had no success.:D

I'm sorry for your troubles, but glad to hear it's not just my truck. If it works out or I find a fix, I'll probaly do a full article on my website about it.

If you also find a fix, let me know too!

Stay tuned...

[VTXSPres]

I somewhat ghetto-rigged mine by splicing into my domelight wire and the ground wire next to it up on the right rear roll bar and then rigged up a separate on-off switch for my domelight so I can turn it off during the day when the cb is on:

http://www.jk-forum.com/showthread.php?t=13899&page=3

No interference at all.

[Flukinuki]

I somewhat ghetto-rigged mine by splicing into my domelight wire and the ground wire next to it up on the right rear roll bar and then rigged up a separate on-off switch for my domelight so I can turn it off during the day when the cb is on:

http://www.jk-forum.com/showthread.php?t=13899&page=3

No interference at all.

What guage wire is the dome light wire? I didn't think the CAN bus would like splicing into any of the factory harness:thinking:

Not trying to flame you or anything but this sounds like a very dangerous way to save a few feet of wire:eek2:

[VTXSPres]

Valid concerns, but it's all properly fused and I've had no issues whatsoever.

The nice thing is that there're no problems with interference.

[Bodo]

Just a quick thought. If it only does it while actually rolling is it possible it's the tire pressure sensors?? Like I said, just quickly browsing through the posts and thought I'd throw something out there.

[Jamooche]

Just a quick thought. If it only does it while actually rolling is it possible it's the tire pressure sensors?? Like I said, just quickly browsing through the posts and thought I'd throw something out there.

Interesting point. I'm not sure how I'd disable or isolate that though. The TPS system does run via wireless radio frequencies.

[Jamooche]

Actually, I don't think it can be the TPS. I dropped one tire's pressure and it let me know on startup with the light and beep.

I'm really thinking it's a MyGig thing...the head unit somehow knows that I am stopped or in motion since it locks out data entry functions.

Fuse M10 is for the "Vehicle off draw - vehicle entertainment system, Satellite Digital Audio Reciever, DVD"

If it works without that fuse and thus Mygig disabled, I found the problem.

[JackMac4]

Yeah sorry to hear you haven't fixed this issue still. Honestly though it's 99% going to be one of three things, as has been discussed. 1 - Grounding issue, 2 - short on the coax, or 3 - alternator whine.

you really should find a radio shop where they can check it out for you. if you're sure all your connections are good, you might think about replacing your coax. get a mutlitester and check the resistance on the coax.

[Jamooche]

I tried that fuse and it doesn't disable the MyGig head unit. So, I took apart the dash again and unclipped the main plug on the MyGig unit thus disabling it. I then ghetto rigged up my CB like I had been testing before with the 3 foot coax and wired and grounded through my aux fuse block:

NO NOISES OR FEEDBACK!!!

I then stopped the truck, turned off the engine, clipped back in the MyGig connector and restarted the engine. MyGig works fine and again:

NO NOISES OR FEEDBACK!!!

It does squelch a bit higher than on my old truck, but definitely in a good area. The yellow dot on the Cobra 75 squelch dial is 1/3 hidden at the bottom. I even plugged in the aux input cord and turned the volume up to max...no PA system anymore!

Why did this fix it (or is it just a fluke)???

A. I reset something in MyGig

B. Adjusting the way the wires were arranged in there (this was with the dash apart and the MyGig unit hanging out) cancelled out some interference.

C. Moving the aux input wire and my Ipod belkin adapter wire away from MyGig cancelled some interference (I did hld the wires up close to the unit in the general location when the dash is closed up, but no feedback resulted)

I'm going to go now and wire the power directly to the battery, reinstall my long coax cable and report back. I'll still be install ing the power and ground noise cancelling device since it does squelch a bit high and that can't hurt anything anyway.

[JackMac4]

I'm guessing B.

[NE Wrangling]

Well that doesn't help me because it was solved based on a fluke... dang

[Jamooche]

Well, it turned out that it was fixed a little with my last post, but not enough. I have further installed both of these:

http://radioproshop.com/filters/nc100.htm
http://radioproshop.com/filters/NF20-NF40.htm

My CB now works perfectly with no interference issues at all. I have done many trail rides and driven in convoys with no problems. I can receive and send at far distances with perfect clarity.

I mounted the power wire box on the trim on the right side of the passenger foot well, and the antenna box under the right panel to the right of the passenger vent.

Let me know if you guys need any more info. or help.

[NE Wrangling]

Thanks, Done ordered both parts as this si the second time these two parts were recommended to me. It's better than 5 hours of labor to have someone try to find the Ignition Noise problem. Greatly appreciated Jamil

[Jamooche]

Thanks, Done ordered both parts as this si the second time these two parts were recommended to me. It's better than 5 hours of labor to have someone try to find the Ignition Noise problem. Greatly appreciated Jamil

No problem. I have the antenna switch set to MAX. It allows me to squelch down the radio to a level much lower than I set it to on my old vehicle. I'm not sure if I'm able to pick up more transmissions, but it works perfectly so far.

Let me know if you need any more help.