[TowerTalk] Multiple tower/stack question

[Jim Lux]

This is an ideal application for a quick and dirty antenna model using any
one of the versions of NEC out there (several nice ones are free: 4nec2 is
my favorite, but there are others).  You don't need to make super duper
models (you're not trying to figure out sidelobes down to -40 dB or measure
input impedance to a gnat's eyelash).  Just model the towers as a single fat
conductor of the appropriate height and diameter, and use some fairly
standard multi element Yagi model (no need to worry about taper, etc. just
get the elements positions and lengths right).

Then, excite the antenna(s) you're interested in and take a look at the
current induced on "other stuff".  If the currents are "small" (compared to
the currents in your antenna), then they'll have a small effect on the
pattern.  You could try looking at the radiation patterns, but to really
believe those, you'd have to make a better effort to model the antenna, and
that will run into more segments, more work, more time.  What you're looking
for is more of a qualitative answer to: "is A better or worse than B or than
C", and for that, looking at the graphical display of induced currents will
work just fine.

Jim, w6rmk

----- Original Message -----
From: <RLVZ at aol.com>
To: <towertalk at contesting.com>
Sent: Tuesday, December 02, 2003 7:13 PM
Subject: [TowerTalk] Multiple tower/stack question


> Hi Towertalkians,
>
> I sure do appreciate you guys as you provide a wealth of helpful tower and
> antenna information.
>
> I'd appreciate your thoughts on how to place multiple towers at a Florida
QTH
> for best HF performance, least pattern distortion, etc.
>
> Such as, if I build 3 towers with monoband stacks on each tower: a tower
with
> 10m stack, another with 15m stack, another with 20m stack.
>
> In Florida we seldom beam due South.  Therefore, would the best
arrangement
> be to place the towers in a direct line from South to North and place the
> lowest freq. 20m antennas on the Southern most tower, 15m antennas in the
middle,
> and the highest freq. 10m antennas on the Northern most tower?  When
antennas
> were beamed North (worst-case) the lower freq. antennas would "see thru"
the
> higher freq. antennas?
>
> Or would there be a better tower placement setup?
>
> Thanks in advance for your thoughts.
>
> Best 73's, Dick- K9OM
> _______________________________________________
>
> See: http://www.mscomputer.com  for "Self Supporting Towers", "Wireless
Weather Stations", and lot's more.  Call Toll Free, 1-800-333-9041 with any
questions and ask for Sherman, W2FLA.
>
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