In most cases when vertically stacking hf antennas you are not looking for
'increased performance' as in adding the two patterns to maximize the lowest
angle lobe or a horizontal pattern. In most cases you are looking to fill
in gaps in the vertical takeoff pattern... those pesky nulls that may fall
in useful takeoff angles into Europe or your preferred target area.
When stacking 2 yagis the best compromise is usually one on top, and one
about halfway down the tower. Its even harder with tribanders, or maybe
simpler, since each band is a bit different there may not be a best spot for
all 3 bands. There may be other slightly better combinations if you land is
not relatively flat, big dropoffs may push the lower antenna down further to
fill in the higher angle gaps. Hills in the foreground may push the lower
one up higher on some bands depending on how close and tall they are.
David Robbins K1TTT
e-mail: mailto:k1ttt@arrl.net
web: http://www.k1ttt.net
AR-Cluster node: 145.69MHz or telnet://dxc.k1ttt.net
> -----Original Message-----
> From: towertalk-bounces@contesting.com [mailto:towertalk-
> bounces@contesting.com] On Behalf Of Gary Slagel
> Sent: Saturday, January 19, 2008 16:15
> To: TowerTalk
> Subject: [TowerTalk] Optimum yagi stacking distance
>
> More questions from a yagi stacking rookie!
>
> I've been using the HFTA software to try and get an
> idea of the optimum distance to stack a couple yagis
> for best performance. I'm stacking 10/15/20
> tribanders for increased performance. I was really
> surprised that on most bands the optimum performance
> seems to be with them separated by only about 10'...
> for instance 65' and 56'! I expected it to be more
> like 20' to 30'!
>
> I wonder how this jibes with folks with real
> experience?
>
> Thanks,
> Gary
>
>
> Gary Slagel/N0SXX
> Lakewood, CO
> http://marina.fortunecity.com/sanpedro/351
>
>
>
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