Cecil
That makes a lot of sense after all if one has the antenna primed for
low angles then propagation will render it useless as time goes by for
those particular angles. If by tipping or feeding another element in an
array you can move or thicken the main lobe you can increase the gain
of a signal by more than 2 S units then it is certainly worthwhile.To
view the subject purely around the maximum gain angle of the main lobe
is fallacious as it is the signal that falls just outside the main lobe
contour that may be the most desirable and subject to the largest
possible gain with the smallest change of TOA. This is because the main
lobe thickens out to cover the deep crevice of non coverage of an array
tuned for a low TOA.and allows you to emulate the performance of a
stacked array with the use of the lower beam alone. 2S unit increase of
a signal that can be barely heard is much more advantageous than
increasing the gain of a signal that is blowing away all other nearby
signals, it certainly allows for more communication data to be
transferred where initially very little could be heard.
If a good contact is underway it is certainly desirable to maintain
that contact even tho propagation is changing and that is what the
original poster is seeking
Art

Cecil Moore wrote:
CW wrote:
I've been wondering for some time now why amateur operators don't build
their Yagi antenna's
so they can be raised and lowered about 10ft in addition to being
rotated.

Many do, using motor driven towers. In addition to lowering
their arrays when a storm hits, some raise and lower their
towers during marginal conditions to maximize signal strength.
--
73, Cecil http://www.w5dxp.com