I run the Cobra 75WX St 40 channel CB. With a 4' Firestik. It seems to work just fine. As said ealier the longer the antenna the further the transmission and recieving. However, the more stuff you'll hit. Make sure you get a spring and an SWR meter.
I like the Cobra 75 because all the controls are on the microphone and the actual unit can be hidden under the seat, or dash, or center console.
There is a good write up at this link
http://www.jeepforum.com/forum/f292/kk-cb-install-write-up-1354307/. I followed it almost exactly, except different paint scheme on the mounting bracket. It works good.
Keep in mind, no matter how long you make your antenna you'll only be able to clearly send out to about 7 maybe 9 miles max (that's on flat open plains). Here is a link to a site that gives antenna length size to broadcast distance,
http://www.rightchannelradios.com/range-approximations-cb-antennas. There will be many times when there simply isn't anybody in the area to respond. I've tested it out in the boondocks and usually get nothing. But it is a good vehicle to vehicle communication tool. So don't depend on it to save you, it's just a nice little insurance.
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(The worst thing you can do to a Jeep...is never taking it off road.)'15 WK2 Ecodiesel Overland (My Overland rig)
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