Art wrote:
"I have mentioned 3 degrees but that was only by eye on print out for a
single element."

I have set the vertical angle of many highly directional dish feed horns
using a bubble level when the path was long. The best setting will be
horizontal so that the signal skims the earth when there are no
obstructions.

Never did subsequent adjustment of elevation angle for best signal ever
alter the bubble setting by one iota.

Why vertical or horizontal? To get the antennas parallel to each other.
That`s why.

All electrical charges exert forces on one another. At great distances,
the forces become vanishingly small. Even so, every effective antenna is
coupled to other conducting matter in its rdiation path to do work in
maintaining periodic motion of charges, however faint, throughout the
universe. Energy transferred by an antenna to the universe is said to be
radiated.

Radiation reflected by the ionosphere surrounding the earth is found to
be scrambled in its polarization (the direction of its E-field).

Energy directly communicated between line-of-sight antennas is most
effective when the transmitting and receiving antenna conductors are
parallel. Conversely, when they are cross-polarized, loss may exceed 20
dB.

Best regards, Richard Harrison, KB5WZI