Looking at these articles about stacking,
http://kyes.com/antenna/stackluge.html
http://www.signalengineering.com/ult...o_phasing.html
one worries about exact cable lengths to not get the antennas out of phase.

But say for a temporary set up, with two small UHF TV yagis, each on a
pedestal that can be moved around the lawn, it seems one can cut the
all three pieces of coax to any short length, and just move the
antennas about, until one gets the best picture, meaning they are then
also in phase, no?

Of course the driven element would be on the same side of each (but by
using opposite sides, the second antenna could be pointed near
directions we wanted to null out?)