Getting SWR down

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projektdotnet

projektdotnet

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Sep 26, 2005
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:bounce: finally installed a CB and for my b-day my in-laws bought me an SWR meter today and a shorter lenth of coax and so I decided to test out my SWR from lastnight's install and what do you know it's over 3:1 :eek:!! So I install the new shorter coax and it dropped the SWR on both ends of the spectrum to below 2.5. Ok that's a start right? I get it to where it is close to both ends but a little on the long side.
Here's the numbers I ran. Since there was quite a few people out there who had their ears on in CH19 I decided not to SWR that channel.

SWR CH40 1.2
SWR CH1 1.5

Is there anything I can do to bring those down further or should I just not worry about it?
 
Here's a good link that may help with your question. http://www.signalengineering.com/ultimate/coax_basics.html

There are a lot of "stories" out there about how coax length affects SWR a great amount. This site should give you a little insight into what may really be going on in your mobile installation when you change coax length and the SWR changes by a lot.

Once you have any feedline problems solved, I would NOT be afraid of an SWR range of 1.2 to 1.5. Of course lower is better, down to 1:1, but some antenna's won't tune below a certain point.

Good luck,

Jeff

N7RYP
 
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I think one of the major differences in the truth from the won't make a bit of difference argument is that with an 18 footer I had a LOT of coiled cable in the pocket but by switching to the 10 footer I had absolutely no coil which I am sure helps. It is a 4ft wilson 5/8 wave antenna that I picked up at flying J. Did some distance tests and picked up a trucker mobile NB about 1.5-2 miles away loud and clear.

Thanks :cheers:
 
Based on the SWR numbers you posted, I would not shorten the antenna. If anything it needs to be longer. Ch 40 is a higher frequency, which needs a electrically shorter antenna. Since your SWR appears to increase as you go lower, if you wanted to lower the SWR, you would need to lengthen the antenna slightly.

If you're using a loaded antenna and it is 4ft or less in length, it's unlikely that you will be able to get the SWR any lower. If it's longer than that, depending on where it's mounted, some further reduction might be possible. However, any benefit from the slight reduction would probably not be noticeable under normal conditions.
 
Make sure your in the open ( NO metal buildings around to reflect signal back ) when your checking. I run a Wilson 4' Silver Load fiberglass antenna on my 40, with an old President Lincoln. On my antenna, the tip is tunable, and has a " ground " wire for matching antenna impedance. Is this the Wilson you bought? On mine, I'm good above 40, and below 1 on 11 meter. Depends on how much effort you want to put into it. Make SURE you have good grounds. When I drove OTR, that was one of the big problems with the newwer trucks, too much fiberglass everwhere. Good luck, Al
 
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