CB Interference Issues

Have you tried tuning with and without the spring? On mine, removing the spring greatly lowered my swr.

 

Some Firestiks are no ground plane some are. The Wilson's have a separate ground wire yes, but has nothing to do with ground plane.

 

Yeah they do all transmitters must have a return path to the radio via the coax. If you just relied on the radio ground you would have ground loops like you would not believe. A CB probably does not have enough nuts to cause issues but any power with no coax ground can and will drive all the electronic in the truck nuts. On any good install the coax must be bonded to the body ground right at the antenna mount. The addition of an extra grounding wire to the mount points to a poor ground at the mount in the first place. Some antennas are wound internally with two sets of windings a 1/4 wave each one is the TX the other is the ground plane it is grounded to the body work this makes the antenna ground plane independent. It is a compromise. Most often you see them on fiberglass body cars and boats. I would not stress over ground planes no vehicle is a good ground plane it is better than nothing but not much good. If you wanted your truck to be a decent ground plane it would have to cover a circle of 36 feet to be OK at CB frequencies. Bottom line a good coax ground to the body and antenna mount is all you need.