CB Radio Question

Okay, so i got a CB radio in my jeep... It's the one from Radio Shack that was like 140 dollars but I got it off of my friend for about 30... Anyways, I got a nice antenna mounted just above the rear right tail light.

Here's the problem: Everytime that I flip it to CB and try and talk accross the CB, I get a nasty screeching/booming noise coming through the car's stereo.

The stereo system is all aftermarket and I do have a 700 Watt RMS amp that runs all of the speakers in the system...

I'm kinda new to the CB radio thing, so if someone could explain wtf is going on and how to fix it, that would be great. Yeah it has all of the squelch and SWF adjustments and crap (not that I know what they do or anything)...

Thanks in advance.

Where did you run your wire for the antenna? I made sure to keep it away from speaker wires, amp wires and any other wires just in case. I don't know if that is the right answer but it is worth a try. I ran the power wire to my amp on one side and the antenna wire down the other, and I have not had the problem you are having. Good luck.

make sure the stereo is off before keyiing up the mic, a strong AM signal broadcast in close proximity to a car stereo will "bleed over" the stereo and when that bleed over comes out of your speakers you have an audio feedback loop between your speakers and your microphone.

in short turn off the stereo when you want to use the CB.

If it is not a strong CB this can have to do with placement of antenna lead/type and the relative position/type of amp leads.

Correct me if I am wrong, but the feedback loop should only happen if the microphone is activated though... If the mic is not activated then the feedback loop would be broken and this problem wouldnt be occuring. So the real question is: does this only happen when you have the mic button depressed (as if to talk) or does it happen whenever the CB is on? If it is only when trying to talk, then you most likely have the feedback loop problem, similar to when you hear the loud whine or whatever it would be called at any event when they are setting up and the speaker/mic are in bad relation to one another. If you tweak the stereo system in different ways this can be decreased to a degree in some situations. Also playing with the input and output sensitivity adjustments on the CB itself (Mic and speaker sensitivity or something, not sure what the real name is, dont even know if you have it on yours, although I assume you do if its an expensive one) can have pretty good results, i had this probelm to a degree and I think I just had to change the mic sensitivity. If you dont know what the different settings are, just make it so it makes the noise, and turn different knobs and see what if anything makes it better or worse

You are not wrong, "keying" is CB language for "activating". There will be no other way that a CB can cause a stereo to "squeal" unless the CB itself is broken and is constantly transmitting.

No it only happens when i "key" the microphone... It doesnt make the noise whenever I just have the CB on.

Damn, I guess I'm just going to have to stick with turning off the stereo when i want to use the CB...

One other thing to look at is, did you tune the antenna? Go to www.firestik.com and read the Tech and FAQ sections and look for the term SWR. If the antenna is not tuned right it can cause feedback into the stereo system. Or you might just have to turn it down to talk.

You definitly do not want the CB antenna wire running down the same path the RCA patch cables are for the amp. If they are you're inviting problems like your describing. On that note you may have a bad ground on the shield of eather cable. On my ex's ZJ I did run both cables down the same side, and had no problems. Cheap RCA's will allow more noise into the signal, and cheap RG-58 (only use RG-58 not 51 or 59)will let signal blead from the wire

You should be able to run them both together. Stray RF can be controller with a little work. Make sure you are running a good quality coax. If you got this coax from your friend and it is old, or if it is the RG-58 (the thin stuff that is about 1/4" thick), get rid of it. Replace it with a good grade of coax. I like the LMR-400 or 600, but it is big, stiff, and hard to work with. Not to mention it is a solid core wire in the high vibration mobile application and it will break easy. But it is low loss and high shielding.... But expensive. Or at least RG-8. most people just install their 20 year old coax and forget about it... You can't do that. It is just like fuel or vacuum line in that it has to be replaced every so often.Try getting some flat steel braided cable with the eyelet connectors on the ends,(or solder them on yourself) and run it from the antenna mount to a solid gounding spot... Like the frame or something. Do the same thing from a screw on the back of the radio to ground. When dealing with RF at 27MHZ..... Grounding is very inportant to getting you system to work correctly. Some people go off the deep end and run these straps from the hood, all the doors, and multible places from the body to the frame to get as close to perfect SWR match as they can. RF travels better over a flat surface then a round one like your coax or a round wire. I run a magnum S-9 to a 2 pill and run the coax right next to my radio and speakers and never have a bit of problems with them. The other side of that is that the input filtering on the radio and/or amp(I would bet the amp) is not so good and no matter what you do, you are fighting an up hill battle. You can try to build a filter on the power lead to the radio and/or amp from some RF chokes. You get 4 (2 packs @ $8.39 each) of Radio Shacks #273-104 snap together RF chokes and some gage wire. I say some gage because I am not sure what gage wire you are using as a power lead. Say it is a 14 gage wire. I like to use the heavy duty speaker wire, that way you filter both positive an negitive wires. Take a, say.... 3' piece of this 14 gage wire and loop it through the 1st choke as many times as you can, say 6-8. Then run it to the second choke and loop it 6-8 time. Through the middle and around the outside. Then the 3rd and 4th. Hook this filter in line with the power to the device being filtered. This will "CHOKE" the stray RF from coming into the device. You should play with the number of chokes. 1 may work or 2 or 3 or 4. I say 4 because that is what I needed to filter out the fuel pump. I did this at the fuel pump on my ranger and it works great. Now if you are running a 6 or 4 or 2 gage wire for the amp, this part number won't work because they are too small, but you can get bigger ones. And when it is all said and done, any one of these or all of them may not take care of it. Sometimes it is just easier to turn the radio off. If you have any questions on RF stuff you can PM me. Good luck!

Also if your radio was "peaked and tuned" this will make a difference. The more wattage you push, the more apt you are to experience bleedover.

Brandon

when my local RV dealer did work on my friends RV, they rewired some stuff and it caused a crazy squeal over the radio. We Tuned it, ran Different Coax... nothing worked. Turned out to be the the power wires of the CB and Radio. Wired them to Different "hot" sources, and all was good again.

If you have RG-58, get rid of it. Install something like RG-8X (also known as mini-8)

I would guess that your biggest problem isnt the CB coax, but the wire used for your stereo setup is probably poorly sheilded. Upgrade your stereo wire to a better sheilded wire and you should be set.

10 bucks says that the ground wire that runs to your CB is too close to ther ground wire for you radio and or AMP.
and... your ANT is not grounded properly...

run separate power and ground to your CB direct from the battery.
Ground the ANT properly.
Tune your system...
and then it will only make a small pop when you key up...

Well what stone dragon said, straight through one ear and out the other... But thanks for trying, i certainly appreciate it no matter how useless it was to me. It's the effort that counts.

Now I'm starting to see what my problems probably are. I'm not going to lie, but I think that the power and ground that my CB uses are the same exact ones that my Head Unit uses. (Wow I'm a fucking dumbass and can't believe I never realized this). Haha. So that's the first step.

Second, now that I really think about it, the antenna wire I got (coaxial) is probably shit b/c i got it at radio shack... It's pretty thin and seems cheap, tomorrow I'm going to go see what type it is.

I'm pretty sure that the RCA cable issue isnt a problem because those are run down the completely opposite side of the car. In fact, they're on the floor, while the antenna wire runs along the roofline and then down along the hatch to the antenna.

Now last question... How does the antenna NEED to be grounded? I've got the bracket directly screwed into the body of the car (just above the top tailight mount, in fact the bracket uses the top bolt for the tailight)... So how does it need to be done...?

Plus, whenever I key the mic, My SWR is really high, like all the way...

How do I tune the antenna and shit? Anyone got a simple explination? I mean, i think that has to do with tuning the antenna, Right?

Sorry 'bout that. Sometime I confuse myself too. Run a set of wires to the battery for the power into the CB. Yes, you have the worlds worst coax. Get some RG-8. It is about 1/2" in dia. Others will have thier own comment and ideas as to what to use, but this is good stuff. Screw that little stuff....IMO but if you must run the small stuff....... As far as the antenna goes..... You have to have a good ground in order for it to function right. If you can get a good gnd off the tail light screw, great. If not, then you have to find a different place to mount the bracket, or you have to run a wire from the ant. bracket to a good solid gounding point. Like the frame. What I said about using the steel braided wire is correct. Call some places and ask them about it. NAPA should stock it. If you can't get it, use a short piece of wire from the bracket to ground. To tune your antenna, first you have to be in the ballpark, and if you are pegging your SWR meter, your system has issues that need to be taken care of first(Like bad coax or a poor ground). Once you can get it below 3:1 ratio,(If you look at the meter, you will see the 1, 2, 3, on the meter scale. These are a ratio and 1:1 is ideal, below the 3 is ok)then you can think about tuning your antenna. To tune it, take a SWR reading on channel 40 and one on channel 1. If your reading is lower on channel 1 then ch. 40, your antenna need to be shorter. If it is lower on ch40 then ch. 1, your ant. needs to be longer. Don't make it harder then it is and if 2:1 is the best you can do, it will work fine. I run a 4' firestix on the XJ and it came adjusted great. Try not to work with crap. Sometimes it's better to just go buy new antenna stuff rather then work with the old junk. 4' firestix $20, mount and nut $12, coax various $. There is other stuff you can do also, but this should get you up and running. I have been doing radio for a long time and know what works and there have been some great ideas listed by everyone. Repost if you need more help. KE7GRI

Just out of curiosity, what side did you put the plastic spacer on, top or bottom?

Check out this site www.cbradioforum.com

I have firestik's door jamb mount that has the 180 degree swivel on it...

I put it over the top of the plastic of the tailight and put that bolt through both the bracket and the tailight, but I also put two screws straight into the body of the car on the top of the firestik bracket.

About 1/2 of the antenna sticks up above the car and that's about what it should be (60%)...

I've seen this set up on a lot of XJs.

got sick of reading all the posts but power source and ground seem to be the first things that jump into my head

What year? I hope its not pre-97.