[TowerTalk] Stacking Tribanders

[Brian Beezley]

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