On Mon, 15 Aug 2011 23:14:19 -0700, Jeff Liebermann
wrote:

On Mon, 15 Aug 2011 08:53:35 +0200, Helmut Wabnig [email protected] ---
-.dotat wrote:

http://imageshack.us/photo/my-images/837/snc14096a.jpg/

Cute cat. However the antenna seems a bit odd. The high carbon steel
tape measure elements are not the best for RF conductivity. Good
enough for receive, but I would check for RF heating in transmit.

The tape measure is also not a circular rod element. You probably
modeled it using a circular cross section. That's probably a good
first try, but if you want accuracy, the actual element cross section
will be needed. That's what I had to do with this stamped sheet metal
antenna:
http://802.11junk.com/jeffl/antennas/mfj1800/

(Without the hair pin match)
http://img5.imageshack.us/img5/3479/snc14112hairpin.jpg
Therefore I put the driver on a slider
http://img841.imageshack.us/img841/8...14097small.jpg

I presume the hairpin match goes between the wing nuts. Looking at
the photo of the hairpin, it seems small for matching a simple 2m
yagi. It's also a good idea to add a balun and to ground the center
of the hairpin match to the center boom.
http://vk1od.net/antenna/misc/BetaMatch.htm


Thank you for the links, appreciate your help.


I fear that in the end I will have to cut and tweak using the
antenna analyzer, and with the time perhaps find
"tape measure correction factors".
Want to keep the design as simple as possible,
and hope it works without a balun or additional tricks.
Am not yet sure if it will work that way, or not.

w.