Stacking and feeding horizontally polarized Yagis is one of the examples that
was developed for the AutoEZ application. The first part of the example
compares a single Yagi mounted at 1.5 WL above real/average ground (blue trace)
with a vertical stack of two Yagis, the second one varying in separation above
the first by 1/8 WL to 2 WL.
http://ac6la.com/ae2msani1.gif
The second part of the example starts with the vertical stack at a separation
which yields the highest gain (7/8 WL) and then duplicates those two antennas
to form a 2x2 array, with the horizontal separation varying between 5/8 WL and
2 WL. Here's what the azimuth plot looks like as the horizontal separation is
changed.
http://ac6la.com/ae2msani2.gif
Finally, the third part of the example models the feed system. In this case
all antennas are being fed in phase via a 4-port power divider.
http://ac6la.com/ae2ms7.png
The complete example may be found in the "2 Meter Yagi, Stack and Feed" section
of this page:
http://ac6la.com/aetltu.html
And the full AutoEZ User Guide is here:
http://ac6la.com/autoez.html
Assuming that all antennas in the array are identical, to test your own
proposed configuration all you need is an EZNEC model of a single antenna.
AutoEZ will take care of duplicating that antenna to one or more other
positions with variable(s) controlling the amount of vertical and/or horizontal
separation. You can also use a different type of feed system if you wish,
choosing from a table of 100 built-in line types (line loss included) and
perhaps setting the line lengths using other variables so you can see how the
pattern and main feedpoint SWR change as the line lengths are changed.
Dan, AC6LA
http://ac6la.com/
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