Question about Cobra 18 Wx St Ii Mobile Cb Radio

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Mobile Cobra CB Squeels on other people's radios when I transmit.

I have been troubleshooting this problem for months...

I have mobile Cobra 18WX-ST-II CB Radio hooked up to a 4-foot Firestik no-ground-plane antenna. I get crystal-clear reception from people miles down the road, but when I transmit, people tell me to, "throw that CB out the window" because all it does it squeal like crazy. Plus, the TX transmit bar goes all the way into the red while transmitting.

I have the no-ground-plane antenna because my car is a 2005 Saturn Ion III, and is predominantly coverd in plastic. The antenna is mounted high on the trunk area of the driver's side, and it is insulated from the car. The coax runs through the trunk and along the floor of the inside of the cabin, up to the CB radio, which is hooked to the bottom of the dashboard of my car. The wire is not pinched in any way, nor is it cross. The connection is solid at both ends. I have tried tuning the end of the firestik, and I have tried grounding it directly to the negative terminal on the battery, even though it's a no-ground-plane necessary rig.

The CB Radio is power through the cigarette lighter with clean, solid connections.I am not picking up RF interference because I have tried the CB radio with the car shut off.

The CB is stock, the radio coax is unchanged, the antenna is unobstructed...

Please, for the love of God, can anyone give me some ideas? Do I perhaps need to find a way to ground the actual CB Radio metal box to the chassis? And if so, how? Could the position of the antenna be poor? Could I have not made solid ground connections even though it's a no-ground-plane rig?

Thank you.

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Change your Mike out. Your AF chip and RF chip is the same chip. If the mike wire is broken and the ground is not releasing it squeals on transmitt. That is why your meter pegs put when you key the mike. Power has nothing to do with it nor does the type of antenna. These things are made so cheap these days all the components are daul purpose. Try this,,, unplug the mike while someone is talking. The speaker will stop working.... it lost it's ground for the AF side of the chip, so when you key the mike it does the same thing but turns it into a RF chip.

Posted on Aug 27, 2009

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Hello winfieldweth,

Have you tried measuring the power output of your radio? If you do, I bet you that the power output is over 4watts PEP. This could be caused by a component changing value over time. What I would suggest you do is to measure the power first to see if the power is over 4watts PEP and then proceed from there. I don't believe it's a grounding issue since the antenna being used is made for a no ground condition. Now if you are planning to use a ground type antenna, I would suggest that you not do that, only because just grounding the antenna will technically do no good, since when the say ground what they are talking about is a ground plane no just a grounding point.

Check your power and then we can start repairing this problem.

I hope this helps, keep me informed on the progress.

Thank you,


Posted on Mar 11, 2009


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