Alan wrote:
Can anyone explain to me why UHF links typically are not LOS while microwave a millimeter wave links typically
are. Does UHF propagate differently? Is it that UHF will scatter off buildings and stuff while microwaves
get absorbed or something? Are there any good books that explain this? Thanks.

Alan

This has been just sitting for a day with no responses so I'll offer an
opinion.

Within the radio Line of Sight Horizon both types of signals are truly
LOS. However, microwave signals generally have a much narrower beamwidth
from the antenna and requires more effort in aligning the antennas at
both ends.

UHF signals have several over the horizon propagation modes which
include ducting, refraction, and weather front modes.

Microwave signals MAY have some atmospheric absorption. This is caused
by self resonance of the nitrogen and oxygen molecules [I believe] in
the atmosphere, and by water vapor absorption. There are major
absorption peaks around 10 GHz and in the high 20s GHz.

Anyone else want to jump in? I'll stand to be corrected on the Physics
issues because I'm an old [really old EE].

Deacon Dave, W1MCE