The combiner performs a mathematical subtraction on the electrical signals arriving from the feedhorns. That subtraction produces the delta signal. A similar feedhorn configuration is used to produce the up/down delta signal (not shown). The waveguide assembly can be used by itself. For a high gain antenna, the feedhorn assembly is located facing the reflecting surface at or near the focal point. For the waveguide image that is shown, the sum signal would be created by a single waveguide feedhorn centered between the two feedhorns that are shown. The sum and delta radio frequency signals are converted to a lower frequency in the receiver where sampling takes place. A signal processor produces the error signal using these samples. The + or − value for each delta signal is created by phase shift of 0 degrees or 180 degrees when compared with the sum signal. A calibration signal is injected into the receive path when the radar is idle, and this establishes a known phase shift between different microwave signal paths (quiescent mode). The angle error is created from the delta signal by performing a complex ratio. This is done for the left/right delta beams, and this is also done for the up/down delta beams (two ratios). An explanation of how real and imaginary parts are used with RADAR can be found in the description of pulse Doppler. The result is a signed number. The outcome of the calibration process is to rotate the complex antenna angle error vector onto the real axis to reduce signal processing losses. The angle error is used to make an adjustment to position the target along the centerline of the antenna. On mechanically steered radar, the vertical angle error drives a motor that moves the antenna up or down, and the horizontal angle error drives a motor that steers the antenna left or right. On a missile, the angle error is an input to the guidance system that positions the guidance fins that rotate the body of the missile so that the target is in the centerline of the antenna. A wheel, mirror and a light can be used to visualize real and imaginary described in this equation. The mirror is placed at a 45 degree angle above the wheel so that you can see the front and top of the wheel at the same time. The light is attached to the wheel so that