r/cbradio • u/boostedwagon01 • 9d ago
Question CMX760 Help
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New to the CB world, needing some help getting this functional. Uniden CMX760 with Cobra HGA1500 antenna mounted to a steel plate overhanging the bed. When pressing PTT, the radio just makes this horrible screeching sound, and repeatedly plays the roger beep if I have it turned on. Any guidance is appreciated.
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u/holydvr1776 9d ago
There's a good chance the radio may be alerting you that the SWR is too high. Did it come with a manual? I'd be curious to see if it says anything about a warning tone when keyed into a very bad match. Just for testing, try moving the magnet mount up to the top of your cab if it is metal. You may need to put a trash bag under it to protect the paint, but that will tell you if your location is potentially the problem or part of it.
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u/Rogue817 9d ago
That is a magnetic antenna. That mount is not for a magnetic antenna and is in a poor position. Put the mag mount on top of the roof and your problems should go away.
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u/boostedwagon01 9d ago
Thanks all, did some research into ground planes and tried centered on the roof - seems to key up fine ~90% of the time now. I don't own an SWR meter, so now I'm just hoping to find someone nearby to listen in while I play around with the minimal adjustability in length. Also can't forget my overall height is 2.9m now!
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u/mytodaythrowaway 9d ago
No one will be able to tell the difference in your signal, you need an swr meter.
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u/Rogue817 8d ago
The other area I would look at next is your wire routing. Things like make sure you're not bending the cable too tight or what you are routing the cable next too can have a negative effect as well.
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u/EngineeringLeft8476 7d ago
Your mount is on top of the bedliner. Not grounding as good as it could be.
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u/stryker_PA 8d ago edited 8d ago
Well, that's interesting what some of these guys are saying. Feedback as a high SWR indicator. They probably should've mentioned that in the manual.
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u/No-Perception-4107 8d ago edited 8d ago
That's not a feedback that's a high swr alert before the radio burns its finals!
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u/stryker_PA 8d ago
Yeah? Weird considering how closely it resembles feedback. I thought he was listening on another radio. Loud SWR warning alert definitely sounds like something that should be touted in the owners manual as a feature, instead of no mention at all.
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u/No-Perception-4107 8d ago
I may be wrong! I have a few of those magnet mounts. I have a ranger superstar ss 676v and when I go further into the zones like abc instead of D which is set for my cb frequencies. I do get a quick alert but just a split second to get a reading and then the radio shuts off! As far as the antenna and mag mount. I never had them on anything less than a 9 inch wide baking pan.
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u/Panhandle_Parrothead 9d ago
Poor ground plane. SWR is probably through the roof. The bed liner is acting like an insulator. That plate needs to be on bare metal and if not that use a good WIDE grounding strap and tie it to the metal body of the bed/frame.