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Old August 16th 11, 07:14 AM posted to rec.radio.amateur.antenna
Jeff Liebermann[_2_] Jeff Liebermann[_2_] is offline
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First recorded activity by RadioBanter: Jun 2007
Posts: 1,336
Default 4nec2 hidden variables.

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


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