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Old 10-17-2013, 10:16 PM   #1
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CB coming through radio

So me and my buddy got our Uniden 510 CB radio kits, and I got everything installed and wired. Power and ground ran through the firewall and straight to the battery terminals. We went out on the road and decided to try them out to see how well they work.

We were on the phone trying to figure out what channel to use, and I was talking to him over UConnect bluetooth. I keyed the mic, and I got feedback through the speakers. Hung up the phone, and my iPod went back to playing, as it's hooked up inside the center console.

When I tried to key the mic again, I could hear myself coming through the car speakers, over the music that was playing. Tried it out on both FM, and while listening to Sat. radio, and it didn't do it over either of them.

Anyone else experience something similar to this, or have an idea on how to fix it? It was ridiculously loud, and would rather not have to turn off the radio every time we're talking over CB.

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Old 10-18-2013, 04:19 AM   #2
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First, double and triple check that your CB is not set in "Public Address" mode, as some CBs have this mode. If the antenna wire is hooked to the PA output this would cause the problem, however then nobody would be able to receive the signal. Since most CBs don't use the same connector for the PA output, this is unlikely to be the issue, but check anyways.

Assuming that isn't the problem...

Your iPod is connected though what is essentially a headphone cable to your stereo. Since headphones use very little power, there is essentially no insulation on this connection. It means that if you "transmit" on the right frequency then your iPod cable will act as an antenna.

If you take 2 wires, both of which don't have enough insulation, and run them near each other you will get "cross talk", meaning that the wire that isn't supposed to have sound on it will get sound on it.

This is what is happening to you, but this shouldn't be happening.

Several wires come out of the back of the CB that could cause crosstalk.

The power wire are not likely the culprit. If you have audio signals on your power wires your head unit is likely toast and probably does not work. You would notice this because it likely would not transmit or receive correctly.

The microphone wire is heavily shielded, and the voltage on it is so low that cross talk could not happen beyond a couple of millimeters of distance.

The only other wire is the antenna wire. This is likely the cause as this is a "high-er" power wire then the others.

CB antenna wires are usually well shielded, since the transmission power is only supposed to "leak out" in the antenna part, not the wire part, of the "circuit" coming out the back of the radio. The only way RF can leak out of your antenna wire, is if either you are using the wrong kind of wire, or a wire of extremely low quality.

I recommend a high quality RG-8X wire with the correct impedance. I have had good luck with this one: RG8X CB Coax Cable | Right Channel Radios

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Old 10-18-2013, 04:32 AM   #3
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Ground should be grounded to chassis, not to the battery as you posted. Not sure if you meant it was grounded to the battery, but it shouldn't be.
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Old 10-18-2013, 07:03 AM   #4
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1) Does this happen on your buddy's system?
2) Where did you mount the CB and run the ant cable?
3) Is the Uconnect system a factory installed unit or did you install it?

There's a chance that where the CB is mounted is too close to either the Uconnect module or too close to the vehicle floor harness causing induced audio signal from the CB or the ant cable. If you have enough play in the wiring & ant cable, I'd try moving the CB from the current location a little at a time while you're talking on it to see if it's the mounting location. If that turns out to be not the problem, I'd start lifting the ant cable away from the current run and possibly even try a different run of the cable.
Another thing is that I have seen people power items up directly to the battery and come out to a dead battery the next day because they accidentally left the item on. You may consider locating a keyed power source. Also as mentioned change the ground to a chassis ground instead of a battery ground.





Quote:
Originally Posted by MSpiegel00 View Post
So me and my buddy got our Uniden 510 CB radio kits, and I got everything installed and wired. Power and ground ran through the firewall and straight to the battery terminals. We went out on the road and decided to try them out to see how well they work.

We were on the phone trying to figure out what channel to use, and I was talking to him over UConnect bluetooth. I keyed the mic, and I got feedback through the speakers. Hung up the phone, and my iPod went back to playing, as it's hooked up inside the center console.

When I tried to key the mic again, I could hear myself coming through the car speakers, over the music that was playing. Tried it out on both FM, and while listening to Sat. radio, and it didn't do it over either of them.

Anyone else experience something similar to this, or have an idea on how to fix it? It was ridiculously loud, and would rather not have to turn off the radio every time we're talking over CB.
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Old 10-18-2013, 09:43 AM   #5
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can someone explain the reason behind chassis ground being better than a direct contact to the battery?
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Old 10-18-2013, 08:43 PM   #6
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Originally had the coax cable running through the middle of the cab, under the back seat, and tucked underneath the center console to the radio, which is located next to the transfer case by my knee. That must have been the issue, cause once I ran it along the wall and under the driver seat instead, the feedback went away. One victory down!


Now, if I could only find a clear area that would allow me to tune the antenna, I'd be a happy man.
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Old 10-18-2013, 09:06 PM   #7
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Quote:
Originally Posted by Captain Ahab View Post
can someone explain the reason behind chassis ground being better than a direct contact to the battery?
It's not, a direct run straight to battery in a 4ga copper or or bigger has a lot less resistance than a steel frame.
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Old 10-18-2013, 11:50 PM   #8
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Quote:
Originally Posted by Txrdstr View Post
It's not, a direct run straight to battery in a 4ga copper or or bigger has a lot less resistance than a steel frame.
Correct. In the ham radio world, we connect directly to the battery with fuses in both lines right at the battery. Frame grounds are used as the RF ground plane for the antenna.

As far as the sound coming through, the poster above is correct with the input cable. It is an unshielded set of wires, and the signals going through are very weak. Your CB output is easily able to be induced into that cable, amplified and sent out of your speakers. Not really much you can do other than disconnect it when on the CB.
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Old 10-19-2013, 09:34 AM   #9
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In an electrical circuit, the (-) side of the battery still has some (+) voltage at the terminal, just less potential. So by going to the chassis for ground that little voltage is drained and the other reason for grounding at the chassis is because of added resistance in the circuit by running a long wire to the battery. The ground wire should ideally be a short as possible to a good grounding point. Usually a bolt, stud or close to a spot weld.


Quote:
Originally Posted by Captain Ahab View Post
can someone explain the reason behind chassis ground being better than a direct contact to the battery?
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Old 10-19-2013, 09:37 AM   #10
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Good, glad you got it taken care of.




Quote:
Originally Posted by MSpiegel00 View Post
Originally had the coax cable running through the middle of the cab, under the back seat, and tucked underneath the center console to the radio, which is located next to the transfer case by my knee. That must have been the issue, cause once I ran it along the wall and under the driver seat instead, the feedback went away. One victory down!


Now, if I could only find a clear area that would allow me to tune the antenna, I'd be a happy man.

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