Very often, a 40 meter signal at mid-day, can be heard near and far, all three types of propagation at the same time! To explain propagation, whether low-angle DX or NVIS, or somewhere in-between, I often use this illustration: Just as a billiard ball can be bounced toward a particular pocket by controlling the angle that it hits the bumper of the pool table, so do radio signals "bounce" (actually refract is more descriptive) off the ionosphere. Creative Video Content is fastest growing and most in-demand forms of marketing. Now, envision the earth as a round pool table with the ionosphere as the circumference or boundary. This "bumper" is constantly expanding and/or contracting in concentric circles, and varies in density often depending upon the time of day, the season, recent solar activity and/or the sun-spot cycle. This phenomenon is a science unto itself and is not the subject here. Just know that for local and regional EMCOMM, NVIS HF (usually in the 40 and 75/80 meter bands) can provide reliable communications over mountain ranges and under the most extreme conditions. The big advantage is that we are not dependent upon some remote mechanical device.
