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Automatic Boresight Measuring EquipmentThe high fineness ratio required by modern boresight radomes has reduced present day radome design to an art rather than a science. The radome designer must have at his disposal some means of rapidly collecting boresight shift data, which he can employ to improve or control a given radome design. This paper describes an automatic boresight measuring system, consisting of a radome mounting fixture, a radar tracking antenna and a null seeking mechanism, which can be employed to provide such data. The automatic boresight measuring equipment is able to automatically collect and record boresight data, cross talk data, and the vector sum of these two as a function of the angle of look. The accuracy of these measurements is better than 0.25 mils. This particular set of automatic boresight measuring equipment can also be employed as a radiation pattern measuring device.
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Electrical Thickness Measurement by a Single-Horn MethodIn order to correct the boresight error of a radome, it is necessary to start with a radome whose walls are uniform in electrical thickness over any given cross section taken perpendicular to the radome axis. It is a difficult problem to manufacture radomes of uniform electrical thickness; therefore, it is desirable to be able to measure the electrical thickness of the radome wall. This measurement may then be used in a control procedure in the manufacture or subsequent correction of the radome. The most common method of making this measurement is by means of a two-horn interferometer. This method is in general satisfactory; however, particularly for large radome of a high fineness ratio, the mechanical problems of maintaining the separation of two horns, one inside and one outside the radome, to close tolerance becomes very difficult. Thus, it would be desirable to obtain the electrical thickness of the radome wall by means of a reflection measurement using only a single horn placed outside the radome. Such an apparatus has been designed and constructed at Hughes Aircraft Company and is the subject of this paper.