Topband: Modeling a shunt fed tower with EZNEC

[Earl W Cunningham]

Ford, N0FP wrote:

"A grounded tower is connected to the model's "perfect ground."  There is
no such thing as perfect ground in real life."
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True.  One of my shunt feed modeling rules tells how this should be done
correctly.
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"Connecting wires of dissimilar sizes will produce unreliable results. 
E.g. connecting an 1/8" wire to a 1' diameter tower is a modeling
problem."
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True.  I've overcome this problem by making every "wire" in the model the
same diameter.  When you begin modeling the tower structure (legs, rungs,
mast, toploading beams, etc.), use the diameter of the actual shunt feed
wire as the diameter of every "wire" in the model.  This technique yields
very accurate results.
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"Another common modeling mistake made is that the individual wires used
in the model have to be oriented such that the segments all line up when
the wires are in parallel.  E.g. The vertical tower portion of the model
needs to be broken up into several wires so that the segments appear on
the tower at identical heights as the 
segments appearing on the shunt wire."
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I agree again.  I usually use about two segments every five feet.  The
segments in the shunt wire automatically line up with the segments in the
tower legs when I do this (the tower is "built" in five-foot sections
with two segments per section.  If the shunt wire is 50 feet long, use 20
 segments in it).  No problem doing this when using EZNEC.

73, de Earl, K6SE