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| CB SWR problem http://www.lostjeeps.com/forum/phpBB3/viewtopic.php?f=45&t=66221 |
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| Author: | thehypnotoad [ Tue Apr 03, 2012 10:51 pm ] |
| Post subject: | CB SWR problem |
Hey guys... I followed this installation idea - http://en.wikibooks.org/wiki/Jeep_Liber ... stallation My AM radio works fine, but I must have a short circuit somewhere because my SWR shoots to 3:1 on every channel. I didn't change any wiring, just installed that antenna in the stock location and installed the firestik am/cb splitter. What am I missing here? |
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| Author: | Zack A [ Mon Apr 09, 2012 1:22 pm ] |
| Post subject: | Re: CB SWR problem |
Did you tune the antenna on the CB channels? |
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| Author: | Draco [ Tue Apr 10, 2012 12:39 am ] |
| Post subject: | Re: CB SWR problem |
I have that setup! First of all, after I installed mine, I went to the CB shop at the local truck stop and paid them a modest amount to tune the system. Ideally you want an antenna analyzer, something like an MFJ-259B, see http://www.mfjenterprises.com/Product.php?productid=MFJ-259B. The frequencies corresponding to the CB channels can be seen at http://www.firestik.com/Tech_Docs/CBFREQ.htm. A technician is going to do something like this: First, they unhook the splitter and just focus on tuning the antenna by itself. Make sure there is no short in the antenna with an ohmmeter. Assuming there isn't a short, tune the antenna by itself. This is done by sweeping the antenna analyzer frequencies between 26.965 MHz (channel 1) and 27.405 MHz (channel 40). Ideally there will be an SWR peak at 27.185 MHz (channel 19). You can move the peak by lengthing or shortening the antenna. The technician who tuned my system did this by screwing and unscrewing the antenna in its mount. If it's way too long, the antenna should have some means of shortening it. I have a simple whip, which can just be cut. If you're getting really bad SWR like 3:1, then something is wrong. Hopefully you're not getting that with a new antenna after you've checked for continuity and shorts. After you have the antenna tuned by itself, then you can plug it into the splitter. You unhook the CB radio from the splitter and again use an antenna analyzer. See following references for some information http://www.firestik.com/Catalog/AR-1A.htm and http://www.firestik.com/Instl-Text/ar1a-pgk-inst.jpg. I think the tuning procedure is similar to that for the antenna itself, except you're turning the potentiometer screw on the AR-1A instead of shortening and lengthening the antenna. I haven't done this myself. I suggest that you pay a technician to look for problems and tune your system the first time. After that you can keep it in tune yourself. My antenna needs tuning at the moment, but I don't own an antenna analyzer and have had to borrow one. I've been meaning to buy one but always have something else that's higher priority. I plan to buy something like an MFJ-266, which also has UHF capability. (Need that for my ham radio). |
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| Author: | audiboy86 [ Wed Sep 12, 2012 7:32 pm ] |
| Post subject: | Re: CB SWR problem |
Check your ground that is the biggest issue usually when that high of a level is detected. Also did your antenna length go up or down? |
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