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Old 07-18-2002, 09:49 PM
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Default CB antenna cable length???

I need to know if there is a standard for selecting antenna cable for my CB setup. I am using a single antenna. I have some RG58au cable. The cable I bought is 9' and it is too short. I need about 12'. What are the acceptable foot multiples for cable? 3 feet, 9 feet, or What?

Thanks,
Tom
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Old 07-18-2002, 10:04 PM
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Default Re: CB antenna cable length???

it doesnt matter TOM.

use the length you need to reach from CB to mount, and use quality connectors, and check the continuity and swr, and its good to go

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Old 07-18-2002, 10:06 PM
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Default Re: CB antenna cable length???

Tom:

When I put mine in I got whatever length they stocked at Radio Shack and just coiled up the excess. I never put a meter on but I've always done it like that with my CBs and they all worked fine. Even on my RV with the whip on the driver's side mirror and the CB to the right of the steering column I just coiled the excess up and zip-tied it out of the way under the dash.

Ken
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Old 07-18-2002, 10:09 PM
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Default Re: CB antenna cable length???

You could easily get a three to four foot piece of cable and join it to the existing cable. You'd have to solder connectors on each end of the cable and of course an antenna connector.

One thing to remember, length does become a factor, as in all things line loss does occur with length. However more it is more important to match the impedeance of the cable. As example. If you are using standard CB Coaxial cable it's RG58U, so get RG58U cable to make up the length you need.

The SWR meter is measuring the impedeance match between the cable and the antenna. The cable impedeance is fixed, about 75ohms, be it 10 feet or 3 feet (for this example). So the adjustment is at the antenna with a loading coil or physically adjusting the lenght of the antenna for a good SWR match.

In fact cable is not too expensive. You should be able to buy a 12 foot seciton for <$8 and the connecors would run about $2 each. Make it yourself... it's not rocket science...and you can easily do the job in less than an hour.

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Old 07-18-2002, 10:20 PM
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Default Re: CB antenna cable length???

Typically I like to use 18 feet for a CB. That gives you 1/2 wavelength between the radio and your antenna. In a SWB Jeep though, that would be hard run that long of a line.

In reality, as long as you have a good ground, and good antenna location, any length will be just fine, and have your SWB tuned well will help matters tremendously.

Whatever you do, don't coil the wire if you have excess, as this will create some RF as the wire will act as an inductance coil. Alos, check with your antenna manufacturer, some of them have a "recommended length".

I have set up about 50 radios in my life thus far (CB, 440cm, 2M, HF, etc), and CB is one of the easier to get a good SWB with regardless of cable length. SWB makes it harder because there is little ground plane, but most jeepers I know only need about 1/4 mile of range anyway for trail running, so I think you will be fine whatever you decide.

--pm
(KC0ITC)
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Old 07-19-2002, 08:09 AM
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Default Re: CB antenna cable length???

I don't normally do this, but I have to respectfully disagree with Leve. Keep in mind that I've had LOTS of problems with RF (from MSD/high output ignition). This is based on my personal experience, YMMV.

1) I've had the most luck with 18' MINI-8 Cable.
2) There's a GREAT primer that will expound more on this than you ever wanted to know at: <a target="_blank" href=http://www.stu-offroad.com/misc/myth-1.htm>http://www.stu-offroad.com/misc/myth-1.htm</a>
3) MINI-8 cable is 95% shielded, and generally has better connectors than standard RG-58, so it's not as susceptable to RF and other "noise" we have in our Jeeps. The price difference between Mini-8 and RG-58 is not enough to really make a difference to me, buy the better stuff.
4) In my setup with 18' Mini-8, a 5' Firestick II (Tuneable) on my Cobra, I get an SWR of about 1.25-1.5.
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Old 07-19-2002, 08:25 AM
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Default Re: CB antenna cable length???

Another thing to note regarding RF... make your ground wire as short as possible. Most of my radio setups have ground that are 4" long or less from the radio.

I have also seen some shielded power leads (like a coax setup with the ground being the shield braid), but I have never needed to use this, so dunno if it helps or not.
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Old 07-19-2002, 08:27 AM
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Default Re: CB antenna cable length???

No disagreement here...



1. The better a shield and drain is constructed into a cable, the better the cable is... RG58U often uses a foil wrap, not the copper braid you see to in the right picture.
2. The cost difference is minimal...
3. The cable is physically smaller, that's a bonus.
4. The connectors are physically smaller.
5. At frequency there is less attenunation per foot.

All in all, it's a very good choice.
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Old 07-19-2002, 08:48 AM
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Default Re: CB antenna cable length???

One other note:

I'm sure it can be done, but personally I haven't had any decent luck with splicing wire, adding barrel connectors or anything else that would mean you aren't dealing with a single piece of wire from end to end.

Heck I was happier than a pig in slop not too long ago, I finally found a hobby shop that sells CB stuff locally. There's a grizzled, crochety old coot that is their radio technician (RC cars, CB, Ham, you name it). I learned a lot, bought a "special" CB, and oh my gawd, I can get a good 5-10 miles out of my junk now...

On a slightly unrelated note, I also found a very cool little accessory for about $1.00. A magnetic mic holder. I bent the pins on it, so it stays on the mic all the time; when I'm done yakking, I just slap the mic on the overhead console, dash, tuffy console, whatever is handy, and it STAYS there. That's WAY cooler than $1.00!!!
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Old 07-19-2002, 10:02 AM
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Default Re: CB antenna cable length???

Length isnt important , if your using a "little extra" help , use RG-8X , if not your usual Radio Shack junk will do , just make sure you solder the shielding to the connectors too . Check SWR and off you go Good Buddy , 10-4 ?

Jeff
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