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post #1 of 36 Old 09-28-2012, 10:11 PM Thread Starter
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Antenna SWR Problem

Hi
I just installed a 3' firestik firefly on a 2012 JK, and I'm not able to get the SWR below 3. Here is what I have done.

I used a Terraflex tailgate bracket. My ground wasn't all that great since it was on a tailgate.
So, I took a 12 ga wire and found a great ground by using the the tie down bracket in the back of the jeep, and also tapping into the sheet metal inside the back door near the wheel well. I ran the wire to my Terraflex bracket. I still had some less than perfect readings so I disassembled, sanded-ground etc, and put it all back together. Things seemed perfect.
I even did a voltage drop test where I got .001

I took the jeep to a field and tried again. I am able to get 1 & 40 almost dead on, but the problem is that the reading is at 3 on the SWR. I was able to get ch. 40 to 2.5 ish but ch 1 was climbing above 3.

What am I missing? It can't be a ground issue. OH,,, when I tested my coax with my multimeter for resistance, I was getting .5 Is that enough to destroy my SWR reading? With all of my other ground test I'm getting close to .1

Any help would be appreciated.
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post #2 of 36 Old 09-28-2012, 10:31 PM
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Wire is not a good ground for RF signals. RF travels across the outside of the conductors, known as "skin effect". A braided ground strap is better.

Did you grind your grounding points down to bare metal before screwing-on the contacts? This will further affect the ground.

Do you have a safari rack or tire swing with a rack, jerry cans, etc? Make sure these items are also strapped to ground as they can cause reflections.

Is there a lot of extra coax coiled up in a loop? This will act as an inductor and will affect SWR.

Did you check your connectors to see if there's any loose strands of braid that might be contacting the center conductor?

Did you install the plastic isolator (washer) on the bottom of the antenna before you screwed it into the mount? Did you perhaps over-tighten the antenna/connector and compress the isolator? The antenna must not make electrical contact with the mount (or any other part of the vehicle). Also check that the connector on the bottom of the mount to make sure it is mounted straight and centered. The isolator should have a shoulder that sticks into the mounting hole to do this, but if things aren't straight it could be a problem.

You could have a bad piece of coax. I've seen it happen. You can't measure impedance with an ohmmeter or via DC voltage drop, it is frequency-dependent. And SWR isn't really related to impedance, but rather mismatches in impedance, which includes metallic objects in close proximity. Try another piece of coax. Run it outside the Jeep to test it first before committing to installation.

Although less likely, it is possible you have a bad antenna or radio. I've never had or seen a Firestick be bad or go bad that didn't show very obvious signs of damage, but that's no guarantee. I've also never seen a radio be bad in regards to SWR, but technically this is also possible.

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post #3 of 36 Old 09-29-2012, 08:00 AM Thread Starter
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Quote:
Originally Posted by BumpInTheRoad View Post
Wire is not a good ground for RF signals. RF travels across the outside of the conductors, known as "skin effect". A braided ground strap is better.

Did you grind your grounding points down to bare metal before screwing-on the contacts? This will further affect the ground.

Do you have a safari rack or tire swing with a rack, jerry cans, etc? Make sure these items are also strapped to ground as they can cause reflections.

Is there a lot of extra coax coiled up in a loop? This will act as an inductor and will affect SWR.

Did you check your connectors to see if there's any loose strands of braid that might be contacting the center conductor?

Did you install the plastic isolator (washer) on the bottom of the antenna before you screwed it into the mount? Did you perhaps over-tighten the antenna/connector and compress the isolator? The antenna must not make electrical contact with the mount (or any other part of the vehicle). Also check that the connector on the bottom of the mount to make sure it is mounted straight and centered. The isolator should have a shoulder that sticks into the mounting hole to do this, but if things aren't straight it could be a problem.

You could have a bad piece of coax. I've seen it happen. You can't measure impedance with an ohmmeter or via DC voltage drop, it is frequency-dependent. And SWR isn't really related to impedance, but rather mismatches in impedance, which includes metallic objects in close proximity. Try another piece of coax. Run it outside the Jeep to test it first before committing to installation.

Although less likely, it is possible you have a bad antenna or radio. I've never had or seen a Firestick be bad or go bad that didn't show very obvious signs of damage, but that's no guarantee. I've also never seen a radio be bad in regards to SWR, but technically this is also possible.
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

Wow, that is a great response. I was starting to wonder if anyone was going to answer. I'll try to respond to your questions one at a time.

Braided strap: OK,,, I didn't use a braided strap. I had read that 10 or 12 ga wire works just fine, so I took the easy route. Obviously some people have had success this way. Something that I will see about changing. It may be easier to find a new place to mount my antenna.

Grind away Powder Coat. Yes I did. In fact, I went back and did it more, and I did get better results with my multimeter. So, there was a problem, but I really don't think it is an issue now.

No Safari Rack or Gas CanHolder. Other than a windshield light bar, no add ons.

Extra coax: No extra. By the time I ran in and out of my tail gate and up the passenger side and across to the bottom of the drivers seat, I only had about a foot left. I was surprised, but that isn't an issue.

Loose Braids: I bought an 18' piece of coax from a truck stop with factory ends. They are sealed. I assume that they are OK.

Mounting Stud: Yep, the plastic washer is in place and snug, not crushed. I even checked with my multimeter to see if the top of the stud was grounded. It is not. That appears to be just fine.

Bad Coax: Well, I have no way of knowing unless I buy another piece. I just moved to SoCal and I don't know anyone to see if I can borrow a piece. I'll toss a post on the California Members section and see if someone will loan me a section of coax for 3 minutes. I don't have a problem buying new coax, I just hate to start replacing parts that don't need to be replaced. It would be great if that was the problem and the fix was that easy.

Bad Antenna: That would suck. My Firestik is brand new and I have no way of knowing if it is good or not, and no way of testing. This will be my last piece to look at.

Thanks for all of your help. I'm not really sure where to start. I feel like I've done everything. Changing the ground strap seems iffy. With so many people not having issues that did it the same way seems like it wouldn't make that much of a difference.
I think I'll grab a hunk o metal and do a mount off of my hood to see if that changes things.

I'm spinning right now because this has caused more problems than it should have.

Thanks again.
Dave
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post #4 of 36 Old 09-29-2012, 09:37 AM
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Yep Bumpinthroad pretty mich summed it up for ya!
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post #5 of 36 Old 09-29-2012, 09:42 AM
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post #6 of 36 Old 09-29-2012, 01:24 PM Thread Starter
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I just realized that I may have left off some important information.

When the adjustment screw is set low on the firestik, I get 1.2 on ch 40 and 3+ on ch1

Not sure if that makes a difference in the info that I gave you.

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post #7 of 36 Old 09-29-2012, 01:46 PM
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Your firestick may need to have some length taken off it when the readings between 1 and. 40 are off.

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post #8 of 36 Old 09-29-2012, 02:07 PM Thread Starter
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Quote:
Originally Posted by v10kingsnake View Post
Your firestick may need to have some length taken off it when the readings between 1 and. 40 are off.
The instructions say "if ch 1 is greater than 40, the antenna is too short."
So I have raised the adjustment screw.
When I do ch 40 comes up and ch 1 goes down. They come together around 2.75
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post #9 of 36 Old 09-29-2012, 03:09 PM
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My swr's changed negatively when I installed a quick disconnect. I haven't removed it yet to see if it will get back to where I was.
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post #10 of 36 Old 09-29-2012, 05:24 PM
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Quote:
Originally Posted by BumpInTheRoad View Post
Wire is not a good ground for RF signals. RF travels across the outside of the conductors, known as "skin effect". A braided ground strap is better.
I just learned that this is really important. Short answer: electrical ground and RF ground are not the same, and don't ground the same. I just got myself a cheap braided ground strap from Autozone, re-grounded my tailgate to the body, and it has improved my reception a bit. It would be even better if I bonded my exhaust, bumpers, etc. Again, separate from electrical grounding, you need RF grounding or "bonding" of the metal parts. Body to frame, bumper to frame, etc.

This website has more radio knowledge than I could know in a lifetime: http://k0bg.com

And here's the article that I am referring to. http://k0bg.com/bonding.html
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post #11 of 36 Old 09-29-2012, 05:55 PM
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Yep. It's also not good to eun antenna next to amperage wires too. Amplifers for stereo systems and other components. Thats why can bus wires are all shielded. Funky stuff starts happening. You cant just use any ole 16ga wires.
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post #12 of 36 Old 09-30-2012, 01:56 AM
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Sometimes a piece of 12AWG or 10AWG wire is all you need to get a sufficient ground, sometimes its not. If cleaning-up your ground contacts made an improvement a strap might get you where you need to be.

The only other thing I can think of is that you might have kinked or bent the coax too tightly at some point during installation and that crushed the foam core, causing the center conductor to get pushed closer to the braid.

You can also try lengthening the antenna by adding a quick disconnect as FireTrail suggested. If you've got the tuning screw all the way out and you're getting close, the couple of inches extra length might get you in the zone. The FireStick (also sold by Quadratec with their brand name) with internal groves is stronger than the cheap knurled QD's with through-slots for the locking pins. The ones with through-slots tend to break from the antenna whipping back-and-forth on the trails.

As for testing the coax, go to Radio Shack and buy another coax assembly. Hook it up without routing it through the vehicle. If this solves your problem then install it permanently and test again. If not, put it back in the box and return it, and look at other problems.

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post #13 of 36 Old 09-30-2012, 05:32 PM
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Inspect the wire that coils around the outer surface of the antenna. I've found a break in that wire with brand new fiberglass antennae before.
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post #14 of 36 Old 10-01-2012, 03:14 PM Thread Starter
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Quote:
Originally Posted by Hickey View Post
Inspect the wire that coils around the outer surface of the antenna. I've found a break in that wire with brand new fiberglass antennae before.


Just checked and I get .5 on a continuity check end to end.
The guy at Firestik said that is a correct reading. So, it isn't the antenna.
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post #15 of 36 Old 10-01-2012, 03:22 PM
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Do you have the stock tire carrier or a bumper mounted tire carrier on a swing arm? My swr was fine until I added the Expo One bumper with tire carrier at which time the tire swing arm and rim became part of the ground plane causing my swr to rise to around 3. I fabbed up an antenna mount for the top of the tire swing to get the antenna above the reflection and swr dropped to around 1 again.

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post #16 of 36 Old 10-01-2012, 03:33 PM Thread Starter
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Quote:
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Do you have the stock tire carrier or a bumper mounted tire carrier on a swing arm? My swr was fine until I added the Expo One bumper with tire carrier at which time the tire swing arm and rim became part of the ground plane causing my swr to rise to around 3. I fabbed up an antenna mount for the top of the tire swing to get the antenna above the reflection and swr dropped to around 1 again.
My JK is bone stock. Factory tire carrier with Terraflex antenna mount.

I even took the spare off, and opened the tailgate to see if there is a difference.
Nope. Same high numbers.
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post #17 of 36 Old 10-01-2012, 03:42 PM
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Did you run a continuity test on your coax to see if the ground-shielding may be contacting the center wire? Also test ground-shield and center wire end-to-end to ensure continuity. Test coax unpluged then test at antenna mount with coax attached.

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post #18 of 36 Old 10-01-2012, 04:08 PM
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Here is my set up. I have since added the spring but my SWR reading are not that good anymore, you would think it would be better but maybe it's the loose contact in the quick release. I also used an 18' firestik antenna cable that was already made up and I didn't have to solder any ends.
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post #19 of 36 Old 10-01-2012, 04:42 PM
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Adding a few extra inches, in my case via a 3" spring, brought my SWR down to 1.1 on Ch. 4 (our club channel). So, like others said, a quick disconnect or a spring, may be an easy fix. If nothing else, they help in other ways.

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post #20 of 36 Old 10-01-2012, 05:03 PM Thread Starter
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Adding a few extra inches, in my case via a 3" spring, brought my SWR down to 1.1 on Ch. 4 (our club channel). So, like others said, a quick disconnect or a spring, may be an easy fix. If nothing else, they help in other ways.
Where were your swr readings before adding the spring?
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post #21 of 36 Old 10-01-2012, 05:05 PM Thread Starter
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Quote:
Originally Posted by Chipewa View Post
Did you run a continuity test on your coax to see if the ground-shielding may be contacting the center wire? Also test ground-shield and center wire end-to-end to ensure continuity. Test coax unpluged then test at antenna mount with coax attached.
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

Everything tested normal.
I have been doing this testing with the radio sitting in my drivers seat. I'm planning on mounting it under the seat when finished. I was starting to wonder if not having the mounting bracket would make a difference. I added the bracket and realized that it is painted and wouldn't ground against metal anyway.

The results were the same with the bracket on.


I'll try a 3' spring as soon as I can find one.
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post #22 of 36 Old 10-10-2012, 06:13 PM
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Quote:
Originally Posted by v10kingsnake View Post
Your firestick may need to have some length taken off it when the readings between 1 and. 40 are off.
That's what I was thinking too. I had trouble with my CB until I made sure I had a good ground (I used 10ga wire) and had my cb radio and antenna tuned. Not sure where you're at in SoCal but I went to a place off Valley Blvd in Fontana. I think it's just called the CB Radio Store. They tuned both my antenna and my radio to my jeep, and they should be able to diagnose any problems if you can't figure it out. It's a good idea to have them tune your radio anyways, and you can get quite a bit more range out of it.

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post #23 of 36 Old 10-11-2012, 07:37 AM Thread Starter
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That's what I was thinking too. I had trouble with my CB until I made sure I had a good ground (I used 10ga wire) and had my cb radio and antenna tuned. Not sure where you're at in SoCal but I went to a place off Valley Blvd in Fontana. I think it's just called the CB Radio Store. They tuned both my antenna and my radio to my jeep, and they should be able to diagnose any problems if you can't figure it out. It's a good idea to have them tune your radio anyways, and you can get quite a bit more range out of it.
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

Mine is mounted on the tailgate just like the photo above. Except other side.
My spring just arrived, and it didn't make a bit of difference, so I'll be ordering a longer antenna.
Grounding doesn't seem to be the issue. The firestik tech told me to attach jumper cables to my coax ring and a good ground. I got the same numbers.
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post #24 of 36 Old 10-11-2012, 08:34 AM
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I would suspect a crushed/pinched cable or faulty stud before a different length antenna. A friend just went through a frustrating install just like yours with the same antenna. His coax tested fine, but we couldn't get below 3 until he replaced the cable and stud.

Pick up a new coax and hook it up without routing it. If it doesn't help the problem, return it.

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post #25 of 36 Old 10-12-2012, 05:54 AM
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Generally speaking, that is a terrible location for the antenna, as a majority of it, particularly near the base, is right up against a bunch of rubber and metal, so it isn't able to properly radiate its signal. I started out with my antenna in the same location and was getting terrible reception, and essentially non-existant broadcast. I then made a bracket to mount my antenna up near the back edge of the hood and was shocked when I turned on the radio to start testing in my driveway and could hear truckers on the freeway, which at its closest point is 5 miles away, and as far as 20 miles by listening to their chatter. I then put the SWR meter on it, and was getting about 1.5 at channel 1, 1.0 on 19, and 1.5 on 40 without even doing any antenna tuning. The location of the antenna is very important. While it looks cooler on the back, it's a bad placement for it functionally.

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