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Old 04-18-2018, 06:36 PM
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SWR antenna tuning troubles?

Ok, I got my power side done and I thought I had figured out my antenna problem. I had a shorted antenna base stud. Got a new one installed today and checked everything with a multi-meter and found no shorts. I think I have continuity everywhere I should, and not where I shouldn't.

So I drove out away from a buildings, power poles, mountains, etc. and setup my SWR meter. Tested channel #1 following the Firestik instructions and got a reading well up over 3.0 in the red, just below the set position.

Then I tested channel #40 and got a slightly lower reading, but still way above 3.0 in the red.

I pulled the antenna cable from the SWR meter and checked for a short on the cable, none. I pulled the antenna cable from the antenna and checked just the cable for a short, none. I double checked the mounting stud and bracket for ground continuity for everything on the bottom side of the antenna mount and cable connecting point. All common to ground.

Then I checked the antenna stud and base above the top side of the mounting bracket for any ground continuity, none.

So, now I have no clue where to go from here?

Any help will be appreciated.

Thanks!

Almost forgot; It's a Firestik 2' antenna mounted on a Teraflex highlift jack mount, on a Teraflex HD tailgate hinge. The jack sticks up about 6" higher than the antenna, and the antenna sticks up about 2" above the roof of the Jeep. 18' of antenna cable lead run in 1/4" wire loom up front to the radio.

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Old 04-18-2018, 06:47 PM   #2
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The antenna stud itself could not have been shorted, but it can short to ground via an improperly assembled antenna mount. A high SWR is generally caused by one of two things... 1) Antenna shorted to ground through an improperly assembled mount, often due to an improperly positioned or missing insulated nylon shoulder washer which serves to insulate the whip antenna itself from the antenna mounting bracket. Or 2) an inadequate RF ground from either or a combination of the antenna mounting bracket not being adequately grounded or the bottom half of the antenna mount not having a bare metal to bare metal to the bottom of the antenna mounting bracket.

This drawing shows where the insulating shoulder washer must be, as well as where a a ring of powder coating must be removed from around the bottom (only) of the mounting hole so the SO-239 part of the antenna mount has a good bare metal connection to a well-grounded antenna mounting bracket.

The parts in red are what I added to clarify where there needs to be a ring of powder coating removed when the mount comes powder coated. Where the mounting bracket bolts to the tub needs to have a bare metal to bare metal connection too. A simple ground wire is not the answer if you don't want to grind paint/powder coating away, though a braided ground strap is usually acceptable if you're just unwilling to start grinding paint/powder coating away.

The bottom line is that in the below drawing, the top most part (3/8" x 24 threaded adapter) is insulated from ground via the insulated shoulder washer. The bottom of the mount called the SO-239 Coax Connector must be grounded via the mounting bracket.
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Old 04-18-2018, 07:19 PM
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Mine is installed exactly like the diagram. The bottom of the mount is zinc/nickle type plating, no paint. I welded that piece to the jack mounting bracket, which is powder coated.

I'm going to clean powder coat from the bracket and the tailgate hinge where they bolt together and see if that helps.

Just so I understand, my first mounting stud piece, when laying on a rubber pad on the bench, then check continuity between the outside of the 239 coax connector and the 3/8" stud was a dead short. It looks to me like there is an internal nylon insulator between those two pieces. I reasoned there had to be, otherwise the flat insulating washer would serve no purpose. Am I not understanding what's taking place?
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Old 04-18-2018, 08:20 PM
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Nope. No go.

I cleaned powder coat off from between the jack bracket and the hinge assembly. Chased the threads of the mounting bolts. Triple checked the bottom of the antenna mount bracket, clean no paint.

Although I can read ground continuity between all the parts mounted on the tailgate and the battery ground, I guess the hinges just don't conduct well enough for a proper RF ground?

I'm going to look for a braided ground strap that would connect between the tub and tailgate. Any other suggestions?

Thanks!
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Old 04-18-2018, 08:57 PM   #5
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Originally Posted by FootSoldier View Post
Mine is installed exactly like the diagram. The bottom of the mount is zinc/nickle type plating, no paint. I welded that piece to the jack mounting bracket, which is powder coated.

I'm going to clean powder coat from the bracket and the tailgate hinge where they bolt together and see if that helps.

Just so I understand, my first mounting stud piece, when laying on a rubber pad on the bench, then check continuity between the outside of the 239 coax connector and the 3/8" stud was a dead short. It looks to me like there is an internal nylon insulator between those two pieces. I reasoned there had to be, otherwise the flat insulating washer would serve no purpose. Am I not understanding what's taking place?
The antenna mount's center stud that sticks up through the hole in the mounting bracket that ultimately connects to the antenna is indeed insulated from the rest of the antenna mount which is grounded.
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Old 04-18-2018, 09:52 PM   #6
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I could not get my readings in the acceptable range either. My antenna was mounted on an ARB bumper with an ARB swing arm tire carrier. I was told it was too close to too much metal causing interference. I moved it and added a ground strap. It got better but never got good. I also got better readings with the cap off the Firestick. Finally took it by a CB shop. He said it was as good as it was going to get so I gave up. Worked good enough for the trails but it wasn’t what I expected.
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Old 04-18-2018, 09:56 PM   #7
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Take the jack off and retest.
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Old 04-18-2018, 10:02 PM   #8
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I also got better readings with the cap off the Firestick.
The SWR will rise from its lowest SWR reading when first installing the cap but if you mis-tune the antenna slightly to the correct side, installing the cap will lower the SWR back down to its lowest possible SWR. Placing the antenna mount higher like at taillight level will eliminate the problem of too much steel from the tire carrier, tailgate, etc..
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Old 04-18-2018, 11:22 PM
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I ordered a flat grounding strap to try and tomorrow I'm going to experiment a little too. I have a set of jumper cables I made out of #2AWG welding cable and I'm going to run a cable from the battery ground to the antenna mount and try that.

I'll also remove the jack and see what I get.

How important is it to go to a location out in a wide open space to tune the antenna?
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Old 04-19-2018, 07:58 AM   #10
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Try another antenna if you can.

Or try adding a length of threaded rod to "lengthen" the antenna. See if that changes SWR. You might even try unscrewing the outer coax until the metal part is not in contact with the mount. Leave the inner coax touching the inner conductor of the mount. See what that does to your SWR reading. Not looking to fix that, but looking for what changes it.

If your SWR is that high, I don't think it is proximity to any body parts causing that.
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Old 04-19-2018, 08:10 AM   #11
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I have the Teraflex HD carrier and for the life of me, no matter what powder coat I removed, I could not get the meter below 3. I spent hours trying to get this setup to work. I ultimately grounded the antenna with a 10 gauge wire to a bolt in the trunk area. That and cranking the Firestik antenna nut all the way down got the SWR to 1.5. Not great, but it is less than 2. This whole process was so frustrating I just left it there. CB works fine.
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Old 04-19-2018, 10:33 AM
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Take the jack off and retest.
Bingo!

My set-up has the antenna 4" lower than the jack and after removing the jack and completing the tuning this is what I got:

Channel 1 = 1.5
Channel 20 = 1.0
Channel 40 = 1.5

Then after tuning the antenna and re-installing the jack, all channels were reading way greater than 3.0.

So, I guess I'll try a longer antenna? I want the radio setup to be as portable as possible, because I only intend to use it for trail runs. I really liked the idea of the antenna being mounted on the tailgate jack mount, because I remove the mount/jack when not heading out to the wilds.
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Old 04-19-2018, 11:07 AM   #13
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Longer antenna will not work, it's still to close to the jack. I ended up using a mount that fit on the left side of the carrier, I got it from Quadratec.
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Old 04-19-2018, 11:27 AM   #14
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Bingo!

My set-up has the antenna 4" lower than the jack and after removing the jack and completing the tuning this is what I got:

Channel 1 = 1.5
Channel 20 = 1.0
Channel 40 = 1.5

Then after tuning the antenna and re-installing the jack, all channels were reading way greater than 3.0.

So, I guess I'll try a longer antenna? I want the radio setup to be as portable as possible, because I only intend to use it for trail runs. I really liked the idea of the antenna being mounted on the tailgate jack mount, because I remove the mount/jack when not heading out to the wilds.
As I did many years ago, but not for antenna tuning reasons, I stopped carrying my Hi-Lift. It hasn't been in my TJ since 2003 even though my TJ is regularly on what many would consider extreme-level trails. No, you don't need a Hi-Lift to change tires. The factory jack works fine changing up to a 35" or even a 37" in a pinch. Plus the factory jack is much faster at getting the tire off the ground than a Hi-Lift is. Really. A Hi-Lift is so seldom the right tool when offroading that few wheelers other than new offroaders believe in them.

Or if you insist on carrying it, just move the Hi-Lift INSIDE the Jeep where it's protected from the elements and its lube won't evaporate. A pair of big u-bolts and wing nuts with some washers holds it nicely to the two rear rollbar bases. It won't affect the antenna tune there.
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Old 04-19-2018, 11:43 AM
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Longer antenna will not work, it's still to close to the jack. I ended up using a mount that fit on the left side of the carrier, I got it from Quadratec.
You know, I'd have thought somebody like Teraflex would have figured that out and not designed to carrier with the antenna mount on it right next to the jack.

Oh well. I can weld, I've got some flat stock, and now I'm motivated!

Thanks!
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Old 04-19-2018, 12:25 PM   #16
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To OP:

Is this the mount you have (photo harvested from Google)?



If so, there is no way you will ever get a good SWR with the Hi-Lift in place. The jack is simply too close to the antenna. Replacing your 2' antenna with a 4' antenna so it extends above the roof line won't help much, if at all.

Your choices are: (1) ditch the jack; or (2) move the antenna mount.

If I were in your situation I would ditch the jack. Someone else in the group will have one (probably never used) in the extremely rare situation when a Hi-Lift is actually the right tool for the job.
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Old 04-19-2018, 12:52 PM   #17
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Quote:
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To OP:

Is this the mount you have (photo harvested from Google)?



If so, there is no way you will ever get a good SWR with the Hi-Lift in place. The jack is simply too close to the antenna. Replacing your 2' antenna with a 4' antenna so it extends above the roof line won't help much, if at all.

Your choices are: (1) ditch the jack; or (2) move the antenna mount.

If I were in your situation I would ditch the jack. Someone else in the group will have one (probably never used) in the extremely rare situation when a Hi-Lift is actually the right tool for the job.


I was just going to say this but you beat me too it.. So instead I will just say that Mr. Bills is a wise man!
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Old 04-19-2018, 01:45 PM
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Originally Posted by Mr. Bills View Post
To OP:

Is this the mount you have (photo harvested from Google)?



If so, there is no way you will ever get a good SWR with the Hi-Lift in place. The jack is simply too close to the antenna. Replacing your 2' antenna with a 4' antenna so it extends above the roof line won't help much, if at all.

Your choices are: (1) ditch the jack; or (2) move the antenna mount.

If I were in your situation I would ditch the jack. Someone else in the group will have one (probably never used) in the extremely rare situation when a Hi-Lift is actually the right tool for the job.
That's the one Mr Bill. I guess I got carrying the high lift because one saved my bacon once upon a time and I don't always roam in a group. In fact, this Saturday will be my first time going out in a group.

The high lift can be a very dangerous tool, but I feel like in some situations it could be very valuable...maybe. I also carry a couple blocks of wood and a bottle jack as well.

I pulled the spare tire and drew up a bracket to move the antenna over to the other side of the tailgate. Ditching the jack would be less work though!
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Old 04-19-2018, 02:24 PM
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Ok, so once again I think I've learned something. Not necessarily what I thought I was trying to learn, but nonetheless I did.

I'm ditching the hi-lift. Years ago I carried in my '72 Chev 4x4 everywhere I went. It saved me a couple times when the factory jack failed. So, years later when I got the Jeep I started carrying it maybe because I thought I was "supposed" to.

But with the suspension these things have today, the amount of droop would probably make lifting from either of the bumpers fruitless because you could easily run out of jack travel before you got the tire off the ground.

Not to mention how unstable a hi-lift can become when the weight is so high up on the jack. (Don't ask how I learned that)

Safer to be low to the ground and lift from underneath.

Oh! And now my radio works fine! Thanks all!
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Old 04-19-2018, 08:24 PM   #20
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I'm ditching the hi-lift.
Good decision.
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Old 04-20-2018, 01:42 AM   #21
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I noticed that it was suggested that getting a longer antenna would not fix your problem. I can not say whether or not this claim is accurate but, the length helped me. I have both a 2' and 5' Firestik and the 5' is able to be tuned perfectly whereas the 2' antenna struggles to perform. My 2' antenna only sticks a couple inches above my roof while the 5' one towers over it. I equated the high SWR with my 2' Firestik being due to reflections from surrounding objects (body, tires, windshield, Hi-Lift, etc.).

The Firestik antennas are top loaded and to get the best results it helps to get the tip as far above the vehicle as possible. Although the mounting position doesn't change with a longer antenna, the coil is able to rise above any objects that will cause high SWR readings.
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Old 04-20-2018, 09:28 AM   #22
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A longer antenna will not help OP because the antenna mount he is using is only a few inches from the Hi-Lift jack, compounded by the jack and antenna being parallel with each other. The reflection of radio waves off the jack is playing havoc with the SWR.

In OP's case a longer, top loaded antenna would improve the "line of sight," which would improve antenna performance for an otherwise properly tuned antenna with normal SWR levels, but that extra length would do little to ameliorate the reflection of radio waves off the Hi-Lift jack because those reflections negatively impact SWR regardless of where they strike the antenna. Perhaps OP could get the SWR down a bit with a longer antenna, but the proximity of the jack and the antenna will always cause problems.

BTW, in my experience shorter CB antennas are always more difficult to tune than longer antennas, even if mounted high with no obstructions.
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Old 04-20-2018, 01:00 PM   #23
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A longer antenna will not help OP because the antenna mount he is using is only a few inches from the Hi-Lift jack, compounded by the jack and antenna being parallel with each other. The reflection of radio waves off the jack is playing havoc with the SWR.

In OP's case a longer, top loaded antenna would improve the "line of sight," which would improve antenna performance for an otherwise properly tuned antenna with normal SWR levels, but that extra length would do little to ameliorate the reflection of radio waves off the Hi-Lift jack because those reflections negatively impact SWR regardless of where they strike the antenna. Perhaps OP could get the SWR down a bit with a longer antenna, but the proximity of the jack and the antenna will always cause problems.

BTW, in my experience shorter CB antennas are always more difficult to tune than longer antennas, even if mounted high with no obstructions.
That makes sense. I just took a look at the TeraFlex mount and it definitely puts it closer than I imagined. I went with a fender mount to try and avoid any obstructions like this. I also just ordered a 3' antenna because I'm about sick of trying to tune the 2' one. Having the 5' antenna is nice because it is easy to tune, but I wanted one I could drive down the highway with.
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Old 04-20-2018, 02:02 PM   #24
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I also just ordered a 3' antenna because I'm about sick of trying to tune the 2' one.
No problem here tuning a half-dozen 2' Firestick FS-2 antennas plus my own several times after various mount/TJ changes over the years.
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Old 04-20-2018, 02:08 PM   #25
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No problem here tuning a half-dozen 2' Firestick FS-2 antennas plus my own several times after various mount/TJ changes over the years.
I might have to check other options then. I have thought about adding some bonding straps to my Jeep because I have heard that can help get a better ground plane. This is my first and only setup so I am learning as I go with reading stuff online.
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Old 04-20-2018, 02:27 PM
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This is my first and only setup so I am learning as I go with reading stuff online.
You and me both brother!
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Old 04-20-2018, 06:27 PM   #27
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I ordered a flat grounding strap to try and tomorrow I'm going to experiment a little too.
Where did you end up getting the grounding strap from? I think I'm going to give it a try.
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Old 04-20-2018, 06:37 PM
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Where did you end up getting the grounding strap from? I think I'm going to give it a try.
Here:

https://www.amazon.com/gp/product/B0...?ie=UTF8&psc=1
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Old 04-20-2018, 07:11 PM   #29
Knows a couple things...

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Where did you end up getting the grounding strap from? I think I'm going to give it a try.
Nearly any auto parts store carries them and pretty much any well equipped electronics store like Fry's will have them.
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Old 04-20-2018, 07:17 PM   #30
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Nearly any auto parts store carries them and pretty much any well equipped electronics store like Fry's will have them.
Thanks for the help. I was trying to google some but there were a few that were $20+.

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