[TowerTalk] Shadowing of small antennas by larger ones?

[Steve]

Good point Tom, I purchased EZNEC to see if metal guy cables would effect
the radiation pattern for a 3 stack for 20m on a 150 ft. tower. I modeled a
single beam then a beam with a boom touching the elements and one not
touching. The model showed radiation from the boom. I then modeled the stack
with a tower and there was more radiation from the tower. I then modeled the
tower with the guy wires insulated from the tower and there was radiation
from the guy wires. The radiation from the guy wires were about the same as
from the tower so I decided to go with steel guy wires insulated from the
tower. The question is how much will the extra metal in the near field and
not so near field effect the antenna and how much do you want to spend to
create a perfect environment for antennas

>
>
> This seems to be going in circles.
>
> Has anyone modeled this or measured it?
>
> It is important to stress that even without resonance a large
> structure  in the nearfield can affect performance greatly. We all
> deal with that every day, but when it comes to antennas we seem
> to toss it all out and assume if it isn't resonant it can't affect the
> system.
>
> I know for sure it will affect the smaller antenna, the question is
> only if it is enough to worry about.  Do any of you know the answer
> with some convincing evidence?
> 73, Tom W8JI
> w8ji@contesting.com
>
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