If you put the array on a rotator and put a receive antenna with some
sensitive output indicator beyond the near field, you can plot relative
field, and thus accurate F/B by adjusting the power to the antenna for same
received F/S at, say, 10º increments. Nothing else should change, so the
relative field strength in the various directions should relate to each
other. Ground reflections and absorption, and all the other artifacts will
be constant unless you change something else.

--
Crazy George
Remove N O and S P A M imbedded in return address
"Dr. Slick" wrote in message
om...
Dave Shrader wrote in message
news:CA44c.6318$C51.52257@attbi_s52...
Interesting photo but NO PATTERN


Opps! Here is the H-plane plot:

http://www.drslick.org/Temp1/yagiplot.jpg


It was an interesting usage of the program, in that we used a
"dummy" reflector that was very far away from the DE, and then used
two directors as reflectors (notice on the plot that the lobe is
actually pointed in the 180 degree direction).


Taking a look at the photo again:

http://www.drslick.org/Temp1/yagi929.jpg

You will notice the 4 turns of 4" diameter coils in the RG-213
coax, just before the feedpoint (SO-239), using a plastic tie-wrap.
You can use a balun instead, but i have never done this before,
perhaps one of you out there has something i could try in the future.
It would be a 1:1 in this case.
You'll also notice that i didn't just leave the coax hanging off
the feed point, as this might ruin the pattern and impedance. I tried
to keep the coax at 90 degrees to the elements by tie-wrapping it to
the PVC.

It would be nice to borrow an anechoic chamber with the proper
field-strength meter, and see how closely the actual unit matches the
YO program in the H-plane.

Great fun, and it should be able to handle up to 500 watts or so,
but i don't recommend using anything more than 1 mW or so... hehehe!

Questions and comments appreciated.


Slick