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Old 01-19-2012, 08:20 PM   #1
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SWR over 5 help

I just bought a cobra 19 cb with a Wilson 4 ft adjustable antenna with 18 ft of coax. I got a mount of eBay that some guy makes. I hooked up the cb and have tried to tune it for about 2 hours now. I have moved the adjustable tip everywhere. I have taken apart the mount a couple of times to make sure its right. Please help I'm pulling my hair out.

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Old 01-19-2012, 09:01 PM   #2
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I don't think that adapter below the coil needs to be there.

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Old 01-19-2012, 11:33 PM   #3
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That's not a coil or an adapter. That's a spring and the coupler nut that's part of the antenna mounting stud. I'd check the SWR without the spring, with the antenna threaded directly into the mounting stud. A spring can make your overall length beyond the adjustment range of your adjustable tip antenna.
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Old 01-19-2012, 11:36 PM   #4
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Nope that's not it. I just tried that. Swr was at about 10 after I moved that adapter. Thanks any other ideas
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Old 01-20-2012, 12:15 AM   #5
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Have you made sure the center conductor of your coax is not grounded and has good continuity from end to end? Then make sure the shield (body of the coax connectors) has continuity from end to end. Lastly, make sure there is NO continuity between the shield and center conductor. If you have a friend that has a CB, try their antenna on your mount. You can check your antenna for continuity from the stud mount to the tip if the tip is metallic, which it should be if it's adjustable.
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Old 01-20-2012, 12:21 AM   #6
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Nope that's not it. I just tried that. Swr was at about 10 after I moved that adapter. Thanks any other ideas
You removed the spring and screwed the antenna directly into the mounting stud? There's no adapter to remove unless you were talking about the spring itself.
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Old 01-20-2012, 08:12 AM   #7
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I have two antennas and they both have the same high readings. I removed the spring and tried it like that and then I removed the metal top of the mount between the spring and the Jeep antenna mount. And still high readings next I. Going to test the coax but how do u do that.
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Old 01-20-2012, 09:28 AM   #8
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I've been having this issue myself...still unsolved. Tried 2 antennas, tried with and without spring, 2 radios, 2 coax connections, adjusted antenna as long as possible and as short as possible...ensured my taillight mount had both a good ground to the body and a good rf ground (ground away paint around all bolt holes to ensure a solid connection AND ran a separate ground wire to the body). Meter shows good continuity from center conductor to center conductor and from outer shield to outer shield. No continuity from center conductor to outer shield.

When I try to tune it... meter pegs at around 8 on all channels. I also get serious engine whine in my radio when I'm driving with it on. I'm assuming either I have a bad ground from my battery to my frame or body or a bad ground to my radio. I've tried various grounding locations to hook my radio ground to though and even ran a ground directly to the negative terminal on the battery. Still no luck...I'm hoping replacing my main ground wires may give me some results. Just haven't done it yet.
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Old 01-20-2012, 09:39 AM   #9
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Going to test the coax but how do u do that.
Get a digital multi-meter (DMM) and set it to measure resistance (Ohms, , continuity, etc.) and place one lead to the center conductor of the coax and the other lead to the threaded collar. There should be no reading between the two. To understand what continuity looks like versus none, just touch the two leads together and you’ll see the difference. Then check from center conductor to center conductor and threaded collar to threaded collar.

You also need to ensure that the doors are all closed when testing and also ensure a good ground for the radio to the Jeep; you cannot rely simply on the ground from the antenna for the radio. Test that the same way you did the antenna (and with it disconnected) but this time there should be a reading.
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Old 01-20-2012, 09:44 AM   #10
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1. Double check you have the jumper cables on the meter set correctly and then that you are using the switch on the SWR meter on the correct setting.

2. If you double check above and all's good then run a ground wire from the antenna base to a good ground on the Jeep chassis, and try again and see if your readings come down.
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Old 01-20-2012, 10:01 AM   #11
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There should be an insulator between the bottom adapter and the antenna mount, just like on top. It doesn't appear to have one.

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Old 01-20-2012, 11:37 AM   #12
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Only one insolater came with that mount and the diagram says to put on top if the mount
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Old 01-20-2012, 01:35 PM   #13
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That would be correct.
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Old 01-20-2012, 04:25 PM   #14
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You do not insulate the bottom connector. This is your contact for the coax sheath. You do insulate the top, the coax core.

I know it ha been said, but, boy, that's a lot of added length with the whole spring get-up.

If you find someone with a nice MFJ meter that has a variable frequency capability, you can try frequencies above and below the band. If you get a good SWR at 20mhz, you know your antenna is just too long and it's not a cable problem.
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Old 01-20-2012, 05:24 PM   #15
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Fixes it with a ground thanks
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Old 01-21-2012, 08:42 AM   #16
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Only one insolater came with that mount and the diagram says to put on top if the mount
Ya.......I just noticed you are conecting your coax with a pl259 connector, if you are hard wiring the coax to the antenna then you need an insulator on both top and bottom.

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Old 01-21-2012, 10:53 AM   #17
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Where can I get another insulator or how could I Jerry rig one maybe with some electrical tape?
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Old 01-21-2012, 01:58 PM   #18
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I now have a ground wire and now the SWR is about 3.5 now what
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Old 01-21-2012, 02:05 PM   #19
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I now have a ground wire and now the SWR is about 3.5 now what

Adjust your antenna tip and see if you can get the reading down further. Use channel 20 to start.
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Old 01-21-2012, 04:29 PM   #20
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Try it without the spring in there, it's adding length. The short fibreglass antenna, are not designed for use with the spring. It should be flexable enough without one, even banging around in the bush.
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Old 01-21-2012, 06:52 PM   #21
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I have a 4 ft adjustable Wilson silverload antenna and the lowest swr I can get is with the spring removed and the adjustable tip removed as well. That gets me to 2.5 on 1 and 3 on 40. But I need the spring because me overall clearance with the antenna is 9ft. I will get a 2ft antenna soon. But I still can't get it lower that 2.5? Should I leave it as is or try to get another plastic washer on the bottom of the mount like Donn said.
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Old 01-22-2012, 01:57 AM   #22
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I believe you have it mounted correct when connecting the coax with the pl259 connector, hard wiring the coax is the only time you need the insulating washer both top and bottom. Is that a wire hanging from the antenna in the second pic?

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Old 01-22-2012, 09:25 AM   #23
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Yea the antenna has a ground as well I have connected it and left it as is. Same reading with or without it grounded.
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Old 01-22-2012, 11:29 AM   #24
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Yea the antenna has a ground as well I have connected it and left it as is. Same reading with or without it grounded.
That lead on the antenna is an impedance adjusting device. It changes the impedance of the antenna to a different value that might more closely match it to the radio / coax / mount system. I would be suspicious of the ground you are using if connecting this lead to that ground does not change the SWR. I would consider the tailgate as no ground at all during this troubleshooting and only use the tub or the frame as a "ground".
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Old 01-22-2012, 11:41 AM   #25
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That lead on the antenna is an impedance adjusting device. It changes the impedance of the antenna to a different value that might more closely match it to the radio / coax / mount system. I would be suspicious of the ground you are using if connecting this lead to that ground does not change the SWR. I would consider the tailgate as no ground at all during this troubleshooting and only use the tub or the frame as a "ground".
This.

Your antenna bracket is painted and sitting on painted metal. You need a good ground from the base of the antenna to the chassis/tub/frame.
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Old 01-23-2012, 11:54 PM   #26
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I know. I now have a ground wire from the antenna bracket, where the washer and lock washer is and that ground wire goes directly to the frame to a known ground where the trailer light harness is.

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