on my Midland 75-822 the hand-held antenna only works when it's running on battery power (not when it's plugged in to the 12V lighter plug). There is a little mod/hack you can do to make it work with a mounted antenna but I didnt want to bother.
I bought 18 feet of coax, a Firestik antenna and a mount, and mounted the antenna on the tailgate. It's really easy to fish the wire and the only hole I had to drill was in the bottom of the plastic center-console. As others have mentioned some companies sell the entire kit with the little CB, antenna, coax, etc.