MIL-STD-469B APPENDIX A
60.2.4.1 The test frequency should be tuned about F M for an optimum response at the receiver output. The test signal level should be reduced to obtain midpulse minimum visible signal (MPMVS) at the receiver
output. The receiver video output should be observed at the output of the video detector using a wide bandwidth oscilloscope. With the MPMVS output established, the frequency and level of the test signal generator should be recorded. The insertion loss of test devices between the point where power level is referenced and the receiver input should be determined.
60.2.4.2 The test signal generator level should be increased to 3 dB above the tuned frequency (F o)
MPMVS level. The generator frequency should be tuned above F o to regain the MPMVS response at the receiver output. This test signal frequency should be measured and noted. This procedure should be repeated
with the generator frequency tuned below F o. The procedure should be repeated above and below F o with the test signal level increased in steps to 6, 12, 20, 40, 60 and, if possible, 80 and 100 dB above the MPMVS sensitivity level at Fo.
60.2.4.3 The procedure should be repeated for frequencies at and near the receiver image response. In
this case, the maximum test signal level should not be required to exceed 60 dB above the MPMVS sensitivity level measured at Fo.
60.2.5 Sample calculations. The selectivity measurement results consist of frequencies corresponding to specified amplitude response levels and associated information such as receiver operating mode, bandwidth and test point. Sample selectivity data forms are shown (see figures 27 through 30).
60.2.5.1 A sample calculation to illustrate the procedure to determine the incremental frequency values and bandwidth follows:
Measured data:
Radar tuned frequency (F ): 3001.868 MHz
Frequency at 6 dB response above F : 3003.655 MHz
Frequency at 6 dB response below F : 2999.997 MHz
The incremental frequency above F o (+ F) is calculated as
+ F = 3003.655 MHz 3001.868 MHz
= 1.787 MHz
F = 3001.868 MHz 2999.997 MHz
= 1.871 MHz
The 6 dB bandwidth (BW) is calculated from
BW = I+ FI + I FI
= 1.787 + 1.871
= 3.658 MHz
60.3 Spurious response.
60.3.1 Objective. The objective of this test is to determine the response characteristics of the radar receiver to signals at frequencies outside the range of the selectivity test.
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