#

The illustration in the vertical axis represents normalized radiation intensity f of theta, in d B from negative 35 to 0 in a decrement of 5 from the bottom to the top. The horizontal axis represents zenith angle theta, in degrees from negative 50 to 50 in an increment of 10 from left to right.

The polar angle theta is positive and defined over the range from 0 degrees (z-direction) to 180 degrees (negative z-direction), and yet the theta axis has both positive and negative values. The right-hand half of the plot represents the variation of F (d B) with theta as theta is increased in a clockwise direction in the x-z plane, corresponding to f equals 0, whereas the left-hand half of the plot represents the variation of F (d B) with theta as theta is increased in a counterclockwise direction at f equals 180 degrees.