(7) Step 7 - If obstructions are present, the antenna mast at the transmit or receive
site, or at both sites, should be elevated to achieve LOS. If this is not possible, radio relays
should be established at all obstruction points. If this is not practical, then consider relocating
one or both of the radio sites to achieve LOS. Examples of completed LOS profiles are
illustrated in Figures 2-3 and 2-4.
d. Figure 2-3 shows two radio paths and their respective LOS profiles. Note that the
lowest altitude in path A is ten feet. At this low height, there may be intervening obstacles, such
as trees, that could absorb and weaken (attenuate) the signal. The path B profile shows the path
dropping below the curvature of the Earth. In this case, a radio repeater needs to be placed
midway in the path.
Figure 2-3. Completed LOS profile
e. Figure 2-4 illustrates two more radio paths and their respective LOS profiles. Path C
shows a profile that does not provide LOS. Looking at the profile for path C, you can see that
intervening terrain beginning at about 17 kilometers from point P blocks LOS between