Can't get good SWR readings with antenna tip on! - Jeep Wrangler Forum
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Old 09-24-2013, 10:56 PM   #1
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Can't get good SWR readings with antenna tip on!

I just set up a CB radio in my Jeep. It's a 2006 Wrangler. I bought the Teraflex mount that mounts to the tub behind the brake light on the passenger side. The radio is a Uniden PRO520XL mounted to the left of my instrument cluster on a Rugged Ridge mount. I am using an 18' coax cable. My antenna is a 3' Firestik II with the tunable tip. I also bought an SWR meter and read up on all of this stuff to make sure I was doing everything right.

The antenna instructions say that I have to check the SWR readings with that rubber tip on the end of the antenna. Firestik site says the same thing. When I do, I just don't get good readings. The best I can get is with the tip screwed all the way in. Even then, I'm getting about a 1.4 on Channel 1, a 1.8 on channel 19 and a 2.8 on channel 40! However, if I take the rubber tip off and retune, I get great numbers. I get a 1.0 on channel 1, 1.1 on channel 19 and a 1.4 on channel 40. I did this out in the middle of a big field with all of my doors closed, RF gain all the way down, and it just doesn't want to work with that red rubber tip installed. Is my antenna still a bit too long? Making it longer only makes all of the readings go way up. My antenna mount is metal on metal, but I didn't grind off any of the powder coating on the mount. I did drill a hole and attach a ground wire from the mount to the tub. I don't think the mount is the problem. Just the rubber tip for some reason. Thoughts?

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Old 09-24-2013, 11:02 PM   #2
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Did you remove any of the powder coating on the mount? I had to file some powder coating off a antenna hole and mounting hole in order to get a good ground. Make a ton of difference.

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Old 09-25-2013, 03:44 AM   #3
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I'm experiencing the same problem with mine. Been searching the web, and can't seem to find anything. I own a 2012, and using a 3 ft firefly with a firestik side mount. Any advise would be appreciated!
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Old 09-25-2013, 10:51 AM   #4
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Had trouble with mine to start with. I too have a side mount and had 3 ft firestik(non adjustable tip). I could not get my numbers down. I called Firestik and spoke with a tech there. He immediately asked if this was a Jeep. Because Jeeps are difficult. He said an adjustable tip 3 ft would be better but would likely still be difficult because of the roll bars and such causing interference. He suggested at a minimum to try a 3ft w/adjustable tip and a 3 inch HD spring. He felt the extra 3 inches the spring provides may be enough. His preferred suggestion was a 4ft firefly(adj. tip). I went with the 4ft and a HD spring. It's a little taller than I prefer and I could cut the height by not using the spring, but the SWR is around 1.5 on 1 and 40.


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Old 09-25-2013, 11:28 AM   #5
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Yeah. I am getting good numbers on mine unless I put that rubber tip on the end. I feel the rubber tip looks a little better and protects the metal end from the elements. But I get a high SWR if I put it on there. I guess it changes the way the antenna vibrates and causes a higher SWR?
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Old 09-25-2013, 05:19 PM   #6
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I have the same cb with a 3' firestik an s homemade mount on the tire carrier. Try leaving the screw off completely and put the cap back on. I have gone on their website and it says to try different combinations. I would make sure you have a good ground by running your own ground wire to the inside body instead of trusting the tailgate for a ground. The rubber tip changes the capacitance of the antenna, that is why they say to measure the swr with it on. Good luck!
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Old 09-26-2013, 12:40 PM   #7
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You can also try tuning it on 20 and check to see if 1 and 40 are acceptable.
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Old 09-26-2013, 08:13 PM   #8
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Yes, you should tune to ch 20. Lowest on 20 is lowest across the spectrum, and should be the bottom of a bell curve, not a line (unless you are tuning for a specific channel).
Grounding an antenna is not like grounding a typical load like a light, it is much more of a bonding. A simple small wire to common ground may be woefully insufficient. A quick test method is to take large gauge jumper cables and clip them to the ant mount and jeep frame, then test again. If your numbers get lower, your bond is not good 'nuff. Usually 2-3 means just that.
As said, try different combinations of removing the locknut or screw to shorten it further than it will now go.
http://www.firestik.com/Tech_Docs/long-tt.htm

Jeeps have plenty of groundplane-able metal, you just gotta get bonded to it.

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