"Ed" wrote in message
. 192.196...

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
Hi Ed

If you are in search of precission, I'd suggest that you consider using 70
ohm coax to feed the 70 ohm antenna. There are some very good 70 ohm coax
available at low cost. Their loss will be a fraction of a dB less than
your RG-8X. Their OD may be smaller (that helps a little to decouple the
stub from the coax). TheVSWR on the 70 ohm line will be lower than on the
50 ohm line. You will then be able to construct a tuning network at the
junction from the transmitter to the 70 ohm line. There will be
essentially no meaureable VSWR anywhere in the system.

Jerry KD6JDJ