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Old 09-27-2007, 01:07 AM   #1
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Angry Dual-Antenna HELP

Hey guys, i got myself RadioShack's Twin-Trucker Fiberglass Dual-Antenna System, and Cobra 19 Ultra lll CB. I almost finished installation of the CB, when i decided to run a SWR test, and i was very disappointed with results. I ran the test on channel 20, and the SWR i got was 2.5

Now before anyone starts guessing the solution to this problem, let me tell you about the installation. I only mounted ONE of the antennas. I mounted it behind the spare tire, right to the aluminum piece that holds the spare. I didn't use any grounding cables, cause common sense tells me that the aluminum tire holder is screwed to the body. The CB power cables are connected directly to the battery. Since i got the dual-antenna kit, the cables were interconnected, so i purchased a single cable. One thing about the cable, the ones that came with antennas are RG-59/U, the one i bought separately is RG-58.

From the pics people posted looks like Amy and Skeeter got the same antennas.

So what could be the problem? Is it the cable? Is it that i only used one antenna instead of two? Could it be poor antenna grounding?

PLEASE HELP ME

This is the link to antenna: http://www.radioshack.com/product/in...tId=2102430&cp

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Old 09-27-2007, 10:56 AM   #2
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Spare tire carrier is aluminum? is that then attached to the rear door? try running a ground from the body to the door, the door may not be getting a good ground.
Have you tried adjusting your antenna yet? what are you getting on 1 and 40?
Do you have excess coax coiled? if so, uncoil it.
Try running the radio ground to the closest chassis ground you can get, it's usually not necessary to run to the battery and the shorter the better.
Don't run co-phased antennas on a Jeep, you need about 9 feet of separation for it to work right. Don't use the coax that came with your co-phased set, it's 75-ohm. ( I see you already got RG-58, good)

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Old 09-27-2007, 06:14 PM   #3
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ya you dont set swrs on channel 20, thats where you want to calibrate the meter at,,,use ch 1 and 40 to set swrs and you would set it by moving the ant. up or down in the housing depending on what the meter reads....did you buy the radio shack swr meter also?? if so you will see the calibrate setting on the front,,some older meters have a calibrate screw

make sure you set swrs with the hood and doors closed and the engine running away from as many buildings as possible
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Old 09-27-2007, 11:56 PM   #4
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Quote:
Originally Posted by skeeter View Post
Spare tire carrier is aluminum? is that then attached to the rear door? try running a ground from the body to the door, the door may not be getting a good ground.
Have you tried adjusting your antenna yet? what are you getting on 1 and 40?
Do you have excess coax coiled? if so, uncoil it.
Try running the radio ground to the closest chassis ground you can get, it's usually not necessary to run to the battery and the shorter the better.
Don't run co-phased antennas on a Jeep, you need about 9 feet of separation for it to work right. Don't use the coax that came with your co-phased set, it's 75-ohm. ( I see you already got RG-58, good)
Let me answer your questions in order. lol

I pretty sure the carrier is aluminum from the way it was drilling, and also the drill dust. Yes it is attached to the rear door. I ran a ground cable directly from body to the antenna mount, almost no improvement, cut SWR by .2
The antenna does not have any adjustment screws. And yes, i did check under the cap at the tip of antenna. =)
After i calibrated the meter on channel 20, i get 2.3 SWR on channel 1, and 3.1 on channel 40.
The whole 20 feet of my cable is used, none coiled.
And no i'm not using the RG-59/U cable, i ditched it right after i got RG-58. Which happened 15 minutes after installing the antenna. =)
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Old 09-28-2007, 12:00 AM   #5
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Quote:
Originally Posted by Teriod View Post
ya you dont set swrs on channel 20, thats where you want to calibrate the meter at,,,use ch 1 and 40 to set swrs and you would set it by moving the ant. up or down in the housing depending on what the meter reads....did you buy the radio shack swr meter also?? if so you will see the calibrate setting on the front,,some older meters have a calibrate screw

make sure you set swrs with the hood and doors closed and the engine running away from as many buildings as possible
I cannot adjust the antenna because there is no adjustment screw, bolt, etc.

Yes, i got the radio shack SWR/Power meter. Here is the link: http://www.radioshack.com/search/ind...kw=21-534&sr=1

I did check it with doors closed and engine running, i just need to find a spot without many buildings on it. lol
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Old 09-28-2007, 10:40 AM   #6
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You adjust fiberglass antennas by trimming the wire under the cap a little at a time, they make em a little long to give you room to work it.
Your SWR shouldn't be starting out that high though, there's something else wrong we need to find first.
Make sure you have the little plastic washers in right, your antenna should be isolated from the mount.
Try running a ground wire from the frame to the mount.
If you can, try a second SWR meter to make sure you don't have a bad one.
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Old 09-28-2007, 06:09 PM   #7
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Quote:
Originally Posted by Seryoga View Post
I cannot adjust the antenna because there is no adjustment screw, bolt, etc.

Yes, i got the radio shack SWR/Power meter. Here is the link: http://www.radioshack.com/search/ind...kw=21-534&sr=1



I did check it with doors closed and engine running, i just need to find a spot without many buildings on it. lol

these radio shack antenaes adjust by the compression fitting that holds them at the bottom---you loosen the fitting and move the antenae up or down accordingly in the tube,,, i just installed one and that is per the instructions on the back of the package,, they have no adjustments on the top or wires to trim

with that meter you set the radio to channel 20 and put the button on cal. the set the needle to the farthest part right of the top red line to calibrate the meter

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