This type of vertical has been popularly used in the VHF and UHF spectrum, and has been called by various names, such as the "Hypodermic" and the "Coaxial" dipole, all variants. The basic principle lies in the fact that a center fed dipole can have a transmission line running thru one of the hollow elements, universally the coax braid side. I have never seen open wire feed in this manner, because the surrounding metal would affect the balance of the line. Coaxial cable is used in all the examples i have seen.
In this case, the dipole is fed slightly off center. No real problem: the upper portion is a regular CB quarter wave whip, usually 102 inches. The lower portion forms the other dipole element. A smaller diameter sleeve is slid into the lower part of the tube element, for resonance/SWR adjustment. I would suggest an 8 foot length for 10 meters.
A 50 ohm length of RG-8 is slid up the center of the tube element, the braid of which is soldered to or bolted to the top of this tube. The center conductor is attached to the whip itself, via the feed-thru mount, which usually has an SO-239 socket. I detached the braid of the coax just below the PL-259 male coax plug, and affixed it to the tube, and just screwed the center wire, with foam insulation and all, to the Whip mount.
This "feed thru" 102" whip mount is affixed to the end-cap of the PVC tube which covers the lower tubular element. The end of the coax that protrudes thru the bottom of the tubular element is, in turn, soldered to an SO-239 coax female socket, which is fitted to the bottom end-cap. Be sure to solder coaxial braid to this socket, too. Keep the coax length such that the bottom can be removed to adjust the SWR sleeve when you tune this antenna. If RG-8 proves to thick, use the mini RG-8, or use RG-58. Note that there is no particular diameter of the lower tube element. I use whatever i find, just so the coax will fit up the center.
Some radials might be connected, attached to the "grounded" part of the bottom SO-239 female plug, to lower the radiation angle a bit.
To tune the antenna, mount to mast as shown in Illust. 2, perhaps a 10 foot standard length. Tie up to a step ladder, and tune to best SWR by sliding the bottom element sleeve in or out. If the sleeve is loose fitting, you might want to drill and screw a machine screw in place to hold it. If you use copper tubing, a solder bead might do the trick once the proper SWR for the portion of the band you want is reached.
Makes for a nice portable camping antenna, it's simple, and looks good when you are finished. As a base, fixed antenna it performs similarly to any of the half-waves i have ever used.
Good Providence in ALL your endeavours! . . . de gary // wd4nka