SO-239 (aka Female PL-259) to BNC Male Adapter Cord.

Here is the perfect cable for those who like to use their handheld CB in and out of their vehicle. Most, if not all late model handheld CB's use a male BNC terminated antenna. While the attached antenna may be sufficient while out-of-doors, that efficiency is severely restricted when you try to use it inside the vehicle. The vehicle body acts like a shield that keeps much of the radios energy from escaping. The best way to maximize the efficiency of your handheld radio when being used from inside a vehicle is to use an external antenna.