[TowerTalk] Modeling a self supporting tower interaction

[Jim Lux]

There's two ways to approach the modeling.  The easiest is to model a "very thick" wire - match the surface area of the tower with the surface area of the wire.
The less easy is to model all the pieces of the tower as individual wires. Since it is repetitious, it's not too tough to model pieces, then use the GM card to make copies. 
I'd bet that some googling would turn up a NEC deck for Rohn 45 tower segments.

Depending on the frequency range, you may want to change the segmentation of the struts and verticals.  

And, of course, runtime for NEC goes as the cube of the number of segments, so you're looking at fairly long run times.

One way to get around that is to do what they do for ships and other structures.  Model the tower and store it as a "Numerical Greens Function" which you can later read back in, and just add your new segments.

When I do this sort of thing, I often wind up writing some python or Matlab code that generates NEC deck cards.  That makes it easy to make frequency dependent segmentation and such.


On Sun, 23 Jun 2024 11:37:36 -0600, Mike Fatchett W0MU <w0mu at w0mu.com> wrote:

Just curious I have an AN Wireless tower and was curious what effect the
tower has on side or ring mounted antennas or even a stack.  My desire
is mostly 6m related.  Element proximity to the tower is a factor.  The
antenna would be a 7 ele FLA 30ft ish so there is a goodly amount of
spacing between elements.

It is one thing to have a 2 or 3 inch mast running through the antenna,
I would love to know what a 2.5 tower face does.  Others have indicated
to me that while it seems like modeling Rohn 45 or a tower would be
reasonable it is not.

Has anyone tried?

W0MU


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