Take a look at this picture, (best I could do with MS Paint) anyway, I had this old antenna, it broke, so I pulled it apart. Interesting to see how the coax coiled and terminated near the top of the vertical section and the shield terminated at the top of the lower section? Note that in the top portion you have isolation with dilectric but no shielding for the center conductor to the top. The upper and lower portions are made of brass and as noted on the drawing they are isolated from each other. Also the coil is interesting, I'm guessing for TX loading? I'm no expert on antennas, I just pulled this apart to see what it was made of. It was originally for VHF airband made by a company called "Celwave" or something like that. Any thoughts? Why was it built this way? What does bringing the center conductor to the top do for you? Any other coments welcome.