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Author Topic: Jeep Liberty Tarheel antenna issue  (Read 3760 times)
N3UJX
Member

Posts: 19




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« on: December 27, 2012, 10:00:05 AM »

Hi All,
I have a homebrew spare tire mount with a tarheel antenna  mounted on it. I am having SWR issues, and am assuming it is a grounding issue. Before changing mount configuration, I was wondering if anybody had any ideas. It seems that I have hit a mental roadblock. The current set up can be seen at the website where I got the idea from.
Thanks
TJ
http://www.myhamshack.com/viewProject.aspx?ProjectID=62
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KM6CQ
Member

Posts: 17




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« Reply #1 on: December 27, 2012, 12:59:14 PM »

Hello,
You did not mention how it tunned on 20 and above. Or what the overall length from the feed point
to the top of the whip is. (thinking about 6 meters)
I do not see a ground plane under your antenna, Just an antenna mount.
Because of that. I think it has raised the feed point impedance of the antenna.
So I think you are right that you have a lot of ground loss.
If you had a antenna analyser your could barrow, that would be a good place to start.
Looking at the size of your Tarheel from the picture, I would think you should be able to achieve 30 ohms at best on 40 and 80.
Then use a shunt matching coil on 40 meters and below to bring it up an acceptable match.

73,   Dan    KM6CQ
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N3UJX
Member

Posts: 19




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« Reply #2 on: December 27, 2012, 03:51:58 PM »

Thanks for the info, I did check it at 20 meters, and it was reading 16 to 1 ,so that's when I realized there was an issue. I was under the impression that the pipe secured to the spare tire mount. I know grounding can be very tricky
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KK4GGL
Member

Posts: 390




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« Reply #3 on: December 27, 2012, 05:47:17 PM »

Hi All,
I have a homebrew spare tire mount with a tarheel antenna  mounted on it. I am having SWR issues, and am assuming it is a grounding issue. Before changing mount configuration, I was wondering if anybody had any ideas. It seems that I have hit a mental roadblock. The current set up can be seen at the website where I got the idea from.
Thanks
TJ
http://www.myhamshack.com/viewProject.aspx?ProjectID=62

There are antenna brackets/mounts that fit on Wrangler spare tire mount. You might want to check to see if they can be used on a Liberty. Also, if you don't have a ground wire running to the body, you probably have almost no ground. All instructions I have seen for mounting ham and CB antennas say that the tailgate is almost completely isolated from the tub.

You can get some ideas from : http://arizonarockyroad.com/
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73,
Rick KK4GGL
WN2C
Member

Posts: 479




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« Reply #4 on: December 28, 2012, 09:25:13 AM »

k0bg. com
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KM6CQ
Member

Posts: 17




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« Reply #5 on: December 28, 2012, 10:06:35 AM »

If mounting the antenna on the tailgate is your desire. I would look at getting the Antenna on the top of the gate making sure the gate is directly under the feed point of the antenna. (Proximity of the gate from the antenna? Center conductor to antenna, shield to tailgate.) This will give you some ground plane. The more mass of metal directly under the feed point of the antenna you have, the less ground loss there will be. (It is a long way from antenna, through the spare tire to the tailgate.) Look at Allen's site K0BG. You would do well to spend some time internalizing some of the relevant information you find there, BEFORE making changes. Keep us apprised with your progress. All of us find this interesting.

Good Luck,   Dan KM6CQ
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N3UJX
Member

Posts: 19




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« Reply #6 on: December 28, 2012, 05:53:28 PM »

Thanks for all the help. I was talking with Roger @ tarheel, and I think I am going to pick up a breed love ball mount. If you are in the the Phila area in the next few weeks, and smell burning paint, I am drilling the hole!
73
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K1CJS
Member

Posts: 6055




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« Reply #7 on: December 29, 2012, 10:35:14 AM »

Have you tried clipping a counterpoise to the ground point on the mount to see what effect it has?  If you didn't check that, how can you be sure the ground is the problem?  Could be that you have a bad antenna.
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M6GOM
Member

Posts: 993




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« Reply #8 on: December 29, 2012, 11:00:55 AM »

The Breedlove mount is the way to go.
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