TC 9-64 _________________________________________________________________________
positions 6 and 10. Maximum brightness occurs at position 8, which is
directly in the path of the flashlight beam. From positions 10 to 12, the
measuring device leaves the flashlight beam and the radiation measurement
falls off sharply. At position 13 the radiation is again at 0 and stays at this
value back to position 0.
forms of electromagnetic waves. Therefore, the measurement of radiation of
an antenna follows the same basic procedure as that just described for the
sun and the flashlight. Before proceeding further with the study of antenna
patterns, you should be sure you understand the methods used to graph the
measured radiation (magnitude of the radiation). Study the rectangular and
polar coordinate systems of plotting presented in the following paragraphs.
4-67. In figure 4-12, view A, the radiation pattern of the flashlight is graphed
in rectangular coordinates. The illustration of the flashlight beam in
figure 4-12, view B clearly indicates the shape of the flashlight beam. This
shape is not evident in the radiation pattern plotted on the rectangular-
coordinate graph. Now look at figure 4-13. The radiation pattern shown in
this figure looks very much like the actual flashlight beam. The pattern in
figure 4-13 is plotted using the same values as those of figure 4-12, view A,
but is drawn using polar coordinates.
Figure 4-13. Polar-Coordinate Graph for Anisotropic Radiator
4-20
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