Abstract: A boresight chamber apparatus employs a near field measurement technique for measuring the amplitude and phase distributions of an antenna under test and then deriving the boresight error from such measurements. The antenna under test is mounted within an anechoic test chamber on a wall of the chamber. Located adjacent the antenna is a near field probe which is moved along a line parallel to the plane of the antenna. The probe, as moved, scans parallel to the surface of the antenna. At prescribed equally spaced points along the line, the amplitude and phase difference between reference signal and the amplitude and phase developed by the antenna is measured. These measured data allow one to calculate the boresight error of the antenna. The probe position is controlled by a computer which also samples the output of the phase comparator at each of the points that the probe is positioned in to thereby derive an accurate representation of the amplitude and phase distributions of the antenna.