Some other things to note is to make sure that what ever you are "grounding" to is i grounded. I have also found in some cases grounding the CB chassis itself help in some cases it didn't. For example on my dodge truck I have a 4 foot fire-stick mounted to the front of my bed rail just ahead of the stake pocket. The antenna mount is grounded to the bed but upon inspection the bed was not well grounded. It did have a strap from the cab to the bed but it was installed post paint. I took the strap off and hit the screw holes with a die grinder to remove the paint, installed the strap and covered with a little rtv for corrosion resistance. Some times you get lucky and don't need to go through all this.
Since there is a lot of threads out there about CB's right now I think I will throw out a couple tuning tips.
When adjusting the antenna: Make sure you take your SWR readings with the vehicle in the configuration you intend to use it in. So if you have doors on make sure they are closed. Make sure the rear gate is closed. etc. Also make sure you readings away from obstructions. I have seen things like power lines, large metal garage doors, and such give odd readings. High school parking lots are good places to tune.
Make sure you or your helper if you have one is not near or touching the antenna when you tune. It will greatly alter your SWR ratings.
Power windows, seats, windshield wipers will more than likely cause noise in your system when they are in use. It can be overcome but most of the time it is not a big deal or worth the trouble.
Don't be afraid to tune for the channel you use most. For my dodge I tune across the spectrum using channels 1-19-40. For the Xj, when was running, and when I do the wifes JK, I will tune with a heavy leaning to channel 4 because that is what most of the people we wheel with use. I will just make sure that it is not way out of whack SWR wise on 1 and 40.
alright thanks, i am also mounting mine on the gear gate. so i will use the same spot, i just bought a cobra 29 and a 3 ft fire stick. should be installing this weekend