On 02 Nov 2008 00:12:29 GMT, Ed
wrote:

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

125 watts forward with 5 watts back is a VSWR = 1.5:1

The characteristic impedance of a coaxial antenna is about 75 ohms.
The best you can do with your present arrangement is therefore about
1.5:1 which is what you're getting.

To do any better, you'll need some way to match the 75 ohm antenna to
your 50 ohm system. That's usually an odd multiple of 1/4 wave coax
section, with an impedance of 61 ohms. Something like:
http://www.repeater-builder.com/rbtip/matchingstubs.html

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

A JPG is worth 1000 guesses.

Also, you might want to do your testing with something less than 125
watts, as accidents and miscalculations might become expensive.

--
Jeff Liebermann
150 Felker St #D http://www.LearnByDestroying.com
Santa Cruz CA 95060 http://802.11junk.com
Skype: JeffLiebermann AE6KS 831-336-2558