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CB radio - coaxial cable length
January 10, 2017
10:46 am
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buckallred
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hi guys:

I am working on the CB/antenna setup in my suburban. I know a little bit about radios, and have read internet forums re: the great debate about the coaxial cable length. Many "experts" (including some who legitimately are experts) recommend an 18-foot coaxial cable to optimize signal, because it is one half the length of a CB radio wave (which is 36 feet long).

I understand that a cable that is of poor quality or that is too short can cause a high Standing Wave Ratio ("SWR"), which, without getting into the technical details, would cause your radio to not work well (poor reception and transmission).

The distance between my radio and my antenna will be very short, such that a 3-foot cable would be more than adequate. I understand (reading various Internet forums and such) that a 3-foot cable simply is not adequate and would cause a high SWR, and that it would be better to use a 9-foot cable and place/wrap the excess into a figure 8 configuration (to avoid or minimize SWR) and tuck it away. I was wondering if anyone here could provide any details on that. It sure would be easy to use a 3-foot cable, but I want to get this right now and not have to mess with it ever again.

January 10, 2017
2:03 pm
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kris_olof
El Dorado
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I bought an 18ft and just have the extra zip-tied in a bundle under the dash.  Didnt do the figure-8 or anything, works fine with little SWR.  When I purchased mine I just grabbed the best cable they had.  All were 18footers so I didn't consider length, just quality.

Where are you mounting your antenna that you can get away with 3ft of cable?

January 10, 2017
2:30 pm
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buckallred
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The suburban has a plastic overhead "console" with storage space in it. . . and already had a hole in the roof (between driver/pass seat) for an antenna. So I am going to attach the CB radio bracket to the plastic overhead console, just above the rearview mirror. The challenge (well, one of several) was to remove the metal bracket that the plastic overhead console bolts to . . . because there was surface rust on the underside of the roof sheet metal. The metal bracket was attached with metal rivets that were a lot tougher than they looked and were a bit of a bitch to drill out.

So I got the bracket off, cleaned off all the rust, then primed and spray-painted the metal. Now I want to install the antenna and antenna holder. Then I will need to reinstall the metal bracket with rivets. It's a lot easier to reach/work with the antenna holder with the metal bracket removed. So here we are.

It's gonna suck if I get it all put back together with the 3-foot coaxial cable, then learn that the SWR is too high such that I have to take it apart and mess with reconnecting a coaxial cable to the antenna in the 1 inch of space that exists between the metal bracket and the roof sheetmetal . . . 

January 10, 2017
3:23 pm
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Dale Clement
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Definitely go with the 18 foot coax, figure 8 or spread out the excess to keep the swr down. Get quality coax and run an antenna that has an adjustable tip for the swr

January 10, 2017
5:46 pm
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Gilbert & Betty
El Dorado Hills
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Remember to have a good ground as well. Don't wind your cable up but like Dale said spread it out if you can in a figure 8.

January 10, 2017
6:29 pm
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buckallred
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Here's a nice response I got from the guy who runs howtocbradio.com:

There are 'some' benefits to having a length of cable that matches the wavelength of the antenna/frequency your operating on (physics is a constant 🙂 ) , but there's also problems with having too much coax hanging around.
 
Taking that extra coax and coiling it in a certain way will change a SWR reading to a desirable level until you move or recoil the coax, giving a different reading all together.
 
The only time I've worried about the amount of coax between rig and antenna is when its going to be a stupidly long length.
 
Go with the 3 foot if it falls into the way you want your setup to run and only consider using a longer length if your SWR is impossible to get down to an acceptable level. A properly constructed CB antenna should match well enough no matter what length of coax you use.
 
I hope this helps and if you have any more questions you can use this email address.
 
All the best
 
Carl
January 12, 2017
10:26 pm
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Jeff_R
Meadow Vista
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At the meeting tonight someone asked about tuning their CB antenna. The below link has a video that explains the process and I have an SWR meter if you want to borrow it.

https://www.rightchannelradios.....structions

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