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Show !o find the factors 0 and </>, the horizontal and vertical beam widths respect ively, a test se_t such as a TS-147 was used, with a feed horn to act as a beacon. The signal was peaked by rotating the antenna in azimuth and elevation until a maximum signal was obtained. Then the azimuth angle was changed until the signal was down 3 db (half power), and the angle noted. The same procedure was used to obtain the half power point in elevation. The value for Pt was checked periodically using a TS-147. The value for the minimum discernable signal, Pr min. , was also periodically checked. In addition, a recording was made of the AGC voltage for various values of Pr, from a TS-147 for the GPG-1, and a built in IF test pulse in the Nike. The remaining factor to be evaluated was antenna gain (G). This was accomplished using a 10 inch aluminum sphere flown beneath a balloon. The technique is based on the work reported by Atlas and Mossop (1960). In the procedure a 10 inch aluminum sphere was tracked and a recording was made of AGC and range. Referring to the equations in Section 2. 0, it is observed that if the received power, Pr' at ·a known range Rt, is known, then using the values of Pt and A obtained previously, where cr is a known constant, it is possible to find G 2 . In most cases the known range used is that point at which the target can barely be observed, and the value for Pr min. is used. Using this pro__ce_<lure, Atlas and Mossop (1960) found that the calculated gain of their antenna was up 3 db. from their observed antenna gain. Initially this was the procedure used in the Park Range program, and the observed antenna gain was also down from the calculated gain. During the 1968-69 season, a graph was prepared using the recorder scale of the AGC as the abscissa and Pr as the ordinate (Figure Bl). When both the sphere recording and the aforementioned record using a test signal were plotted, a wide disparity was noted in the results. Referring to Figure B2, it is noted that for scale values of : : : 10 the curves are in fairly close agreement in value and slope, while for scale values of < 10, the curve for the sphere drops rapidly and the test signal curve is more gradual. These results would indicate that there is a great deal of error introduced if the value for Pr min. is used at the range where the radar lost track. This error is undoubte-dly ,d ue to a pointing error for small values of Pr· To eliminate this error, the value for Pr was found by comparing the unknown sphere record at a point on the scale equal to a known test set signal. At this same point the range is also known; therefore, one can solve for antenna gain G. Using this procedure, the observed antenna gain was found to be equal to the calculated antenna gain. The values for Pr used in the compute_r program ca_n be translated fro1:1 a __ plot of AGC scale to p as shown in Figure B2. It 1s apparent from this fig ure that the relationship between Pr and AGC scale is non linear and is moS t precisely solved by using this graph. 351 |