How do you measure accuracy?

We measure accuracy under very controlled conditions that are designed to eliminate multipath reflections. The DF antenna is rotated on an index head and the bearing angles are recorded at 1 degree intervals. The error at each angle is then calculated and the mean and standard deviation computed. This process is repeated at other frequencies across the bandwidth of the antenna. The mean of the error corresponds to the calibration angle and the standard deviation is stated as the “one-sigma” error value.