The radiation or antenna pattern describes the relative strength of the
radiated field in various directions from the antenna, at a constant
distance. The radiation pattern is a reception pattern as well, since it also
describes the receiving properties of the antenna. The radiation pattern is
three-dimensional, but usually the measured radiation patterns are a twodimensional
slice of the three-dimensional pattern, in the horizontal or
vertical planes. These pattern measurements are presented in either a
rectangular or a polar format. The following figure shows a rectangular
plot presentation of a typical 10 element Yagi. The detail is good but it is
difficult to visualize the antenna behavior at different directions.