The whip antenna is 72" long from Radio Shack. It packs down to about 15" once the threaded coupler is attached. The coupler is a 5/16" threaded coupler modified to fit and hold the antenna whip.
The threaded coupler is modified by drilling out some threads to make space for the antenna base to slide in. A small hole was drilled in the side and threaded (6-32) for the set screw. Positioning the antenna is a little tricky - you want to make sure the set screw is tightening down on a solid part of the antenna base while leaving enough room for the bottom thread
