I just spoke to the Firestik CB Antenna people. The AR-1A device that they manufacture was designed to let an AM/FM radio and a CB radio use a single CB antenna. They told me it uses diodes to separate the circuits (so the 4 watt CB energy wont fry your radio).
I am thinking, and the Firestik people say this "should" work, of using a scanner in place of the AM/FM radio. So I could have both the scanner and a CB with only one additional antenna on the car.
Has anyone done this? If so, any comments? TIA.