It could be 1 of a thousand. The wire that is wrapped around the antenna may be broken. Check all of your connedtions. Especially if you are using a spring and or your antenna mount may be loose or something. I have know of some antenna's that had to be grounded. Some come from the factory with an external ground wire that you can ground back to the mount. When you turn the radio on do you get squelch when or is it quite??
You can take a jumper wire and hold it to the base of the antenna and then find a good ground on the jeep.. If you hear a difference on the radio this could be the problem.
You can also buy a Francis antenna that needs no adjustment for about 18 bucks at most t-stops.. I have a 4' and I have no problems at all. Unless no one has said anything. I use a Cobra all in one and I am not too impressed but it serves the purpose and it saves space.
When I drove a truck I ran a Cobra 29 Limited LTD Classic with dual francis antennas and a 300 watt linear.. Could talk about 12 - 15 miles on a clear day.
I run a small uniden and a firestick on the camper and it does okay. If you don't have it figured out by River Rock I will be glad to help check it out. I have a spare firestick in the shop that I have used before. I can bring it and see if it helps. i may also have some coax. If so I will through it in the camper..
One thing for sure.. It is only about 3 componets..
Radio, Coax, Antenna.. easy uh....
Just some ideas...