"Tom Ring" wrote
From page 810 of Terman`s 1955 edition:
"Space-wave Propagation. At frequencies above about 30 MHz, the
ionosphere is not able to refract energy to earth, "
It is comforting to note that the ancient ones were wrong about some
things. It may not happen daily, but it happens a lot at 6 meters, often
at 2 meters, and sometimes even higher.
____________

The term "space wave propagation" does not necessarily mean that the wave
has to be reflected from the ionosphere (or anything else) to be useful.
Microwave systems, FM and TV broadcasting, aeronautical communications,
satellites, and many other point-to-point systems at VHF and above all use a
space wave. Reflection/refraction of it whether from the ground,
structures, or (occasionally) the ionosphere are not always beneficial to
those systems.

RF