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got the 1/4 wave whip and a 2.5-3.0 swr. need help

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blakews2217

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so i had a Wilson 1000 for a few months till the twist lock decided to twist off at about 85 running down the interstate. thank god i was not keyed up then. i got home and looked at the ability of the 102" whip, and decided for 35 bucks i can build my own mount for it. got the antenna, built and isolated the antenna side from the body, (its mounted on a custom rear bumper). ran a ground strap from bumper to audio amp ground (frame ground). ill add pics when i get the time. my buddy tested the radio on his base antenna and came at 1.2 on ch 1 and 40. made it to the next town over (about 12-15 miles) without an amp. so the radios fine. also tested the meter on his setup and it backed what his other meter said. . its got a fresh antenna cable. im running out of ideas and have no money for it right now. the radio is a midland 1001z from amazon. any ideas are welcome.
 

mmckenna

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Pictures would help.

There can be a number of sources of high SWR, and narrowing it down to which one is going to take a bit of work.

Comparing your SWR meter to your buddies was a good step, we can cross that off the list.

Rather than us typing out pages of suggestions, we'll wait on the photo to give a good starting place.
 

blakews2217

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https://uploads.tapatalk-cdn.com/20170429/59b15aa78c13c303a2929b0a94adc955.jpg https://uploads.tapatalk-cdn.com/20170429/0953de3f7903dc37022ed60669a9f10e.jpg https://uploads.tapatalk-cdn.com/20170429/858f88a9396650fc7b2dafe9bf1ec559.jpg

Here's some pics. That black square is a plastic Insulator so the antenna won't short to ground. The ground strap is on the barrel connector of the antenna cable. The cable runs on the floor of the jeep. It's quite the task to re-locate the antenna because it's mounted to a 3/16 inch think bumper tube. Also, I know testing in my driveway isn't the best way to do it but I'm cheap and gas is expensive so I'll test it bit until I find what works.


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RFI-EMI-GUY

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so i had a Wilson 1000 for a few months till the twist lock decided to twist off at about 85 running down the interstate. thank god i was not keyed up then. i got home and looked at the ability of the 102" whip, and decided for 35 bucks i can build my own mount for it. got the antenna, built and isolated the antenna side from the body, (its mounted on a custom rear bumper). ran a ground strap from bumper to audio amp ground (frame ground). ill add pics when i get the time. my buddy tested the radio on his base antenna and came at 1.2 on ch 1 and 40. made it to the next town over (about 12-15 miles) without an amp. so the radios fine. also tested the meter on his setup and it backed what his other meter said. . its got a fresh antenna cable. im running out of ideas and have no money for it right now. the radio is a midland 1001z from amazon. any ideas are welcome.
1) Insufficient Grounding? The photos of the bumper mount and ground strap would help.

2) Poor connections at antenna or radio PL259?

If the above are OK

3) Carefully Test VSWR on Channel 1, Channel 18 and Channel 40 and record values. If the VSWR improves on a Channel 40 then the whip is too short. If it improves on a Channel 1, the whip is too long.

4) Set radio to Channel 18 and shorten or lengthen (as determined in 3 above) the whip using setscrews (if available) until you have better than 1.5:1 VSWR. (See link bottom page for more hints)

5) Check channel 1 and 40 and see if they are the same or warrant adjustment as in step 3 above.

It may turn out that you need a spring or spacer to resonate at Channel 18 27.185 MHz.

Also Read this page:

http://electronicenergysource.com/get_low_swr_from_102_inch_whip.htm
 
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blakews2217

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1) Insufficient Grounding? The photos of the bumper mount and ground strap would help.

2) Poor connections at antenna or radio PL259?

If the above are OK

3) Carefully Test VSWR on Channel 1, Channel 18 and Channel 40 and record values. If the VSWR improves on a Channel 40 then the whip is too short. If it improves on a Channel 1, the whip is too long.

4) Set radio to Channel 18 and shorten or lengthen (as determined in 3 above) the whip using setscrews until you have better than 1.5:1 VSWR.

5) Check channel 1 and 40 and see if they are the same or warrant adjustment as in step 3 above.


The pics are up as soon as the forum mod approves the post. The set is as fallows for today.
40:1.6
18:1.8
1:2.0



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mmckenna

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OK, RFI-EMI-GUY has some good ideas.

Here's what I'll add to his:

The ground strap needs to be as short as possible. The shorter the better.
Probably isn't necessary if the bumper is properly attached to the frame, but it should hurt.

1/4 wave length on CB is about 108 inches, so a 102" whip on it's own is going to be resonate (low SWR) above the CB frequencies.
The 102" whips are designed to have a 6" tall spring between the base of the whip and the antenna mount.

Also, having the whip that close to the jeep body is going to cause some unwanted reflections. While it's not an easy solution to fix, it can throw things off a bit. Don't move it until we tackle everything else.

Check the coaxial cable from end to end. Make sure it's not damaged, pinched, cut, etc.

If you have access to a multimeter or a continuity tester, you can perform the following tests:

1. Disconnect the coax from the back of the CB and the antenna base. Using the meter or continuity tester, check for a connection between the center pin of the cable connector and the outer ring. There should be NO continuity. If there is, you have a short circuit in your cable or one of the connectors. Fix that.

2. With the coaxial cable disconnected as above, check for continuity between the center pin of the cable connector and a known good ground on the vehicle body. There should be NO continuity. If there is, your cable is cut, pinched or otherwise damaged somewhere.

3. With the coaxial cable disconnected as above, Using a long piece of wire, test for continuity between the center pin of the coax connector on the two ends of the cable. There should be continuity between the two center pins. If there isn't, there is a break in the cable somewhere. Could be the cable has been cut, or the connectors are bad.

4. With the coaxial cable disconnected as above, test for continuity between the outer ring of the coaxial cable connector on one end to the far end. There should be continuity. If there isn't, cable has been cut or there is a problem with one (or both) of the connectors.

5. With the cable still disconnected, test for continuity between the 102" whip antenna and vehicle body ground. There should be no continuity. If there is, then there is an issue with your antenna mount.



If all of those check out, then the issue is likely with the antenna length or coupling between the antenna and the jeep body.
 

mmckenna

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The pics are up as soon as the forum mod approves the post. The set is as fallows for today.
40:1.6
18:1.8
1:2.0
That's actually not too bad.

Important part is to make sure your vehicle is well away from other obstructions, as that can impact the SWR. Sometimes it's a good idea to go out in the middle of a parking lot to do your testing.

So, if anything, those SWR readings would suggest the antenna is a bit too short. Try loosening the set screw and pulling the antenna up a bit. See if SWR improves.

Also, those SWR readings suggest that your antenna mount and coax are probably OK.
 

blakews2217

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1) Insufficient Grounding? The photos of the bumper mount and ground strap would help.

2) Poor connections at antenna or radio PL259?

If the above are OK

3) Carefully Test VSWR on Channel 1, Channel 18 and Channel 40 and record values. If the VSWR improves on a Channel 40 then the whip is too short. If it improves on a Channel 1, the whip is too long.

4) Set radio to Channel 18 and shorten or lengthen (as determined in 3 above) the whip using setscrews (if available) until you have better than 1.5:1 VSWR. (See link bottom page for more hints)

5) Check channel 1 and 40 and see if they are the same or warrant adjustment as in step 3 above.

It may turn out that you need a spring or spacer to resonate at Channel 18 27.185 MHz.

Also Read this page:

http://electronicenergysource.com/get_low_swr_from_102_inch_whip.htm


I fallowed the link and found my antenna is 8 1/2 too short. Come Monday I'll machine a solid extension for the base.


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blakews2217

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Got a thin shop in the rain, took it to a parking lot with that pice of rod taped to the antenna. 1:1.0
40: 1.25.
I'd like to get it perfect now so I don't have to come back to it. Thanks everyone for the help



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mmckenna

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I fallowed the link and found my antenna is 8 1/2 too short. Come Monday I'll machine a solid extension for the base.
3/8 X 24 thread.

Before you machine an extension, you may want to try some all-thread and a coupler and try it first. Cutting antennas to length will get you close, but each individual install will vary. Length isn't the only thing that impacts SWR.

Each individual install will be different and require different lengths to get lowest SWR. Making something adjustable out of scrap first would be a good idea. Once you know for sure exactly how long the length needs to be, then machine up a permanent solution.
 

blakews2217

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I can acualy build the extension to be adjustable. Male and female ends with a jam nut to lock it in. Also, easy access to a machine shop is a godsend.


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mmckenna

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Easy access to a machine shop is a godsend.
Yeah, that's what I figured. Might as well if you've got the resources.

I can acualy build the extension to be adjustable. Male and female ends with a jam nut to lock it in.
That would work. Just make sure it's strong enough to not bend if you hit a tree branch on the trail.

A spring might still be a good option if off roading is your intended use.
 

blakews2217

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Yeah, that's what I figured. Might as well if you've got the resources.







That would work. Just make sure it's strong enough to not bend if you hit a tree branch on the trail.



A spring might still be a good option if off roading is your intended use.


I tuck the antenna under a roof rack while off the road. I use cb on road and walkie talkie off road. Easier and cheaper.



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mmckenna

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Got a thin shop in the rain, took it to a parking lot with that pice of rod taped to the antenna. 1:1.0
40: 1.25.
I'd like to get it perfect now so I don't have to come back to it. Thanks everyone for the help
I missed this post earlier.

That's pretty dang good right there. That would indicated that all is well other than the antenna length. Sounds like that will be an easy fix for you.

Any idea why it was reading so high earlier?
-Be careful water isn't getting in the coaxial cable connections. Tape up the one under the bumper really well. Water in there will throw your SWR off and eventually damage the cable.
 

n9mxq

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The thick black block, is it just on top of the bumper? If there's nothing in the hole to insulate the mount bolt from the bumper, well.. you get the idea..
 

blakews2217

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The thick black block, is it just on top of the bumper? If there's nothing in the hole to insulate the mount bolt from the bumper, well.. you get the idea..


The black block is only on top to stop the antenna from contacting the bumper. It's a mid grade uhmw plastic. There's a small bit of electrical tape to stop the antenna stud from contacting the bumper as well. It's completely isolated. I messed with it a. It more and got 1.15 and 1.1. I'm happy with that. Now to measure and build an extension. I'd like to say thanks to everyone who replied. I found that my highschool parking lot is big, open, and few light poles. Here's a satellite pic. I sit right in the middle.



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n9mxq

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If there's nothing insulating the hole, expect problema

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blakews2217

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If there's nothing insulating the hole, expect problema

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I edit the prev. Post to include my shady fix. Thin strips of electrical tape for now. I'll make a plastic insulator for the stud when I make the adjustable extension.


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n9mxq

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The mounts you buy have them. I've ran plenty of 102s without issue on store bought mounts. Wish you luck.. And if you're driving and your receive drops off, don't transmit..

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blakews2217

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The mounts you buy have them. I've ran plenty of 102s without issue on store bought mounts. Wish you luck.. And if you're driving and your receive drops off, don't transmit..

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That's how I knew my old Wilson 1k fell off. Hearing great then dead air, not even static with the squelch all the way down. Pulled over and saw no antenna. Turned the radio off and kept going.


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