[TowerTalk] [CQ-Contest] Stacking on separate towers, take off angles?

[Dan Maguire]

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/