"Jeff Liebermann" wrote in message
...
On Sun, 8 Nov 2009 19:06:49 -0600, "amdx" wrote:

Ok, here are some more pictures. If anyone is so interested that they want
to
model the antenna I'll post picures or dimensions or both of the antenna.
But not today.

cm and mm if possible. The reason I suggested graph paper is that I
can usual compensate for parallax with graph paper, but not with just
a ruler.

http://s395.photobucket.com/albums/pp37/Qmavam/

Much more better photos. Thanks. However, I can't measure the length
of the coax "balun" with any of those pictures. I would like to check
your calcs for the 0.66 wavelengths, especially since I don't know
from where to where you measured. (Hint: from coax shield to coax
shield. Everything else is a radiator and/or series inductor).

You forgot to list one:
http://s395.photobucket.com/albums/pp37/Qmavam/MFJNconnector.jpg
That's 6 mm of exposed center conductor (including the center pin)
plus more at the ground lug (under the ruler). Guessing some more...
A 1mm dia wire, 6 mm long = 3.0 nH.
http://www.consultrsr.com/resources/eis/induct5.htm
At 2.4Ghz that's
XL = 2PiFL = 2 * 3.14 * 2.4*10^9 * 3.0*10^-9 = 45 ohms
of series reactance. With a 50 ohm "load", that's not going to help
make a very good match.

Modeling asymmetrical Yagi elements is not my idea of fun. I should
learn how to do it since I designed a similar sheet metal stamped Yagi
for 900MHz in about 1983. However, that was done with guesswork,
cut-n-try, a bit of plagiarism, and lots of midnight snarling.
Incidentally, to improve the bandwidth, it would have be trivial to
round off the ends of the elements. There are also some rather odd
effects caused by the width of the "boom", which doesn't follow the
usual round boom Yagi model. Oh well.

I can't find a photo of my stamped metal Yagi, but perhaps a
description might be interesting. I mounted a right angle N coax
connector centered on the "boom" at the driven elements and facing
towards the reflector. The driven elements were also stamped
aluminium. I used a gamma match consisting of a piston trimmer cap
mounted on one of the drive elements, and a heavy copper wire from the
cap to the center pin of the N connector. That was covered with a
clam shell plastic radome.


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

Here is a drawing and some more pics.
http://i395.photobucket.com/albums/p...intFileJPG.jpg
http://i395.photobucket.com/albums/p...connection.jpg
http://i395.photobucket.com/albums/p...MFJRuledDE.jpg
http://i395.photobucket.com/albums/p...Jruledcoax.jpg
Hope I covered everything, I'll be back on late tomorrow to check.
Mike