I'm trying to build a decent performing 2M coaxial skirted antenna and
have a question about its design for maximum efficiency.

I based the "hub" on an SO-239 connector. I soldered my RG8X cable
center conductor to the solder pin center conductor and brought the
shield braid out in two places.

I cut a 19" piece of half inch copper pipe, cut 4 half inch slots on
one end, fanned the slotted end out slightly to fit nicely against the
SO-239, and slid this pipe over my coax and up to the SO-239. I brought
the two braid lengths previously prepared out through two of the rather
fat slots, soldered the pipe to the SO-239 and the braids were soldered
to the pipe where they came protruded out the slots.

I soldered an 18 1/2" brass welding rod to a PL-259 center conductor
and screwed that the the SO-239 for my radiator. The copper pipe assy
and coax slide nicely down into a length of 3/4" PVC . This makes a very
nice break-down package for transportation and portable work.

Back to my question: I am measuring about 125 watts forward and 4-5
watts reflected at my desired frequency ( 146.000 ). While this may be
acceptable to some, I would like to get the match down to 1:1 SWR.

Are there any design deficiencies in my proto-type? Can anyone
suggest something I might try to improve the match? Is there a "rule of
thumb" regarding the construction of such antennas?... length of coaxial
skirt vs. antenna element?

I appreciate any feedback on this. Thanks.

I suppose I could provide a picture if anyone requires it....

Ed K7AAT