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Old 06-27-2013, 12:03 AM   #1
Join Date: May 2013
Location: Seattle
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CB Firestik red cap disrupting signal?

First post: (I did a search and didn't see anything)

CB Antenna install on a 2013 JKU, mounted in back next to spare tire.

So I was tuning my 3' firestik antenna. I was using a professional SRW meter. Weird thing, without the "red" cap I was getting a reading of 1.2 once I put the cap on the reading went up to 2.0. I tried another 'tip" from another Firestik antenna & had the same issue.

Anyone else have this issue? Anyone know why? I dont believe it was pressure related. It seems odd that the company would use a material that would change the signal. I tried some other materials (heatshrink) and had no signal disruption.
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Old 06-27-2013, 04:57 AM   #2
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I noticed a slight change in SWR readings when I put the cap on, but don't think it was as significant as what you saw. I went from 1.2 to 1.6 on ch1 and ch40. Went from 1.3 to 1.7 on ch20.

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Old 06-27-2013, 07:51 AM   #3
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That's normal.

Firestik's documentation will tell you to take your SWR readings with the cap on and tune accordingly.
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Old 06-27-2013, 11:00 PM   #4
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Originally Posted by Jag View Post
That's normal.

Firestik's documentation will tell you to take your SWR readings with the cap on and tune accordingly.
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Old 06-29-2013, 06:09 PM   #5
Knows a couple things...

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That thick vinyl cap adds electrical capacitance to the antenna which slightly detunes it by making it look electrically longer. When tuning the antenna (setting its length), simply tune it so it is off to one side of minimum SWR by shortening the antenna a little more than gives minimum SWR, enough so when you install the cap, it brings the SWR back down to where you want it.
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