Radar antenna measurements using the sun

The use of the sun for verifying alignment, pattern, and gain of operational surveillance radars is described. The basic measurement is of the solar noise. A sample radar IF signal is obtained from the radar receiver and input to the combination of IF amplifier, detector, low-pass filter, and digital meter. Data must be collected over a period of about one hour to obtain measurements over a 15-deg sector of the antenna's elevation pattern. Data reduction involves converting the time of the measurement to the sun's position and to convert the measured voltages to antenna gain. These procedures are described, and an example of how the data collection and reduction methods were applied in a particular case is described. Antenna alignment in azimuth and elevation may be checked to a fraction of a degree and peak gain may be measured to an accuracy of about 1 dB. The method requires little test equipment and no calculations beyond the capacity of a pocket calculator.