spaced, concentric circles. In this example, they are numbered successively

from 1 to 10 from the center out. These circles are used to indicate the

magnitude of the radiation.

4-63. The advantages of the polar-coordinate graph are immediately evident.

The source, which is at the center of the observation circles, is also at the

center of the graph. By looking at a polar-coordinate plot of a radiation

pattern, you can immediately see the direction and strength of radiation put

out by the source. Therefore, the polar-coordinate graph is more useful than

the rectangular-coordinate graph in plotting radiation patterns.

4-64. Most radiators emit (radiate) stronger radiation in one direction than

in another. A radiator such as this is referred to as anisotropic. An example of

an anisotropic radiator is an ordinary flashlight. The beam of the flashlight

lights only a portion of the space surrounding it. If a circle is drawn with the

flashlight as the center, as shown in figure 4-12, view B, the radiated light

can be measured at different positions around the circle. Again, as with the

isotropic radiator, all positions are the same distance from the center, but at

different angles. However, in this illustration the radiated light is measured

at 16 different positions on the circle.