Here's how TA handled stacking:
---- STACKED ANTENNAS ------------------------------------------
TA can plot the pattern for a pair of antennas with
vertical and/or horizontal offset. First snapshot the pattern
with the antenna at one stacking location. Then move the
antenna to the other location and press C. TA will plot the
pattern for the two antennas excited with equal current
magnitudes. Press B to toggle between BIP (both antennas in
phase) and BOP (both out of phase). Press C to toggle between
stacked and individual patterns. Vary antenna height with
stacking enabled to find optimal stacking distance.
TA assumes the isolated, free-space, antenna patterns
aren't affected by mutual coupling between the antennas. This
isn't quite true for most antennas at typical vertical stacking
distances, but usually only the rear part of the pattern is
affected in a minor way. However, interaction can be large when
stacking horizontally if one antenna fires directly into
another, even when the antennas are separated by some distance.
Use AO or NEC/Wires to accurately determine gain and pattern
degradation for stacked antennas over flat earth.
TA uses pattern integration to establish array gain.
This provides realistic gain, even for small stacking distances.
However, TA needs the complete elevation pattern for accurate
pattern integration. Therefore it doesn't allow restricted
analysis range when stacking antennas. TA inhibits changes to
certain other parameters while stacking to maintain the same
modeling environment for both antennas.
Brian
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