NOTE: If no LOS path exists, discard this site proposal and choose a
new tentative site, repeating the procedures listed above.
(5) When profiling confirms the suitability of Radio Repeater
1, move from it to determine the location of Radio Repeater 2.
Continue until you reach Radio Terminal B.
c. LOS Profiles. One of the best ways to determine if your site
locations provide an efficient LOS path is "profiling." There are two
methods of profiling used to determine the existence of a usable LOS
path for your multichannel radio system.
(1) You can determine the existence of an LOS path using a
profile map of the terrain on a nonlinear graph.
Nonlinear graphs
take into account the refraction caused by the Earth's atmosphere.
Figure 2-5A shows an exaggerated LOS path on a true Earth radius
scale.
Note that the true LOS path curves with respect to the
theoretical LOS (broken line). Figure 2-5B shows the Earth's radius
expanded to 4/3 of its true size. The 4/3 radius compensates for the
Earth's atmosphere's refraction.
Figure 2-5.
LOS paths
Figure 2-7 illustrates examples of graph paper for plotting profiles.
Note that there are two 4/3 graphs. You use the top graph for sites
of up to 5,000 feet. Use the lower graph for sites with elevations
of less than 5,000 feet.
To plot using
nonlinear
graph
paper,
perform
the
following
procedures:
(a) Determine
the
scale
for
the
elevation
and
distances
involved.
2-11
SS0016
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