MIL-STD-469B APPENDIX A
30.3 Signal generator outputs contain harmonics of the fundamental frequency. These harmonic outputs should be attenuated in order that false receiver responses will not be produced. In particular, low pass or bandpass filters of known insertion loss at the fundamental frequency of the generator should be used when spurious responses are being measured at frequencies well below the receiver tuned frequency. This technique is used to attenuate generator harmonics to levels below the sensitivity of the receiver.
30.4 Many signal generators exhibit some leakage that is particularly noticeable when the attenuator is near its maximum attenuation setting. Low-leakage signal generators should be used to perform measurements. Adequate shielding, separation and power line filtering should be employed to eliminate the possibility of erroneous results caused by improper coupling of the signal generator. The signal generator leakage signal level should be at least 6 dB below the indicated attenuator setting.
30.5 For receiver measurements, the receiver input coupler should be a shielded network whose insertion loss is known to within 1 dB at the measurement frequency when it is terminated in its nominal impedance. The coupler input impedance should properly terminate the signal source (VSWR less than 1.3:1) independent of load.
30.6 The frequency of signal generators supplying test signals should be determined to an accuracy of plus or minus 2 parts in 106 unless other accuracy requirements are given in a specific test. The overall output calibration of the signal generator should be correct within plus or minus 2 dB at any attenuator setting.
30.7 The calibration of attenuators external to signal generator should be known within 1 dB at each measuring frequency when it is terminated in its nominal impedance. The attenuator should have a VSWR less than 1.3:1 independent of load when driven by a 50 ohm source. The requirement of attenuator calibration may be waived if, in the calibration process, the attenuator insertion loss is included as part of the signal substitution source.
30.8 Frequency selective voltmeters should be calibrated as two terminal voltmeters at all measurement frequencies by reference to standard signal generators. Frequency selective voltmeters used in these measurements should be monitored by aural as well as visual indicators. An oscilloscope should be used as a visual indication device to ensure that the frequency selective voltmeter indications are due to signals and not noise (especially applicable to pulse measurements).
30.9 When making measurements requiring recovery of pulse characteristics on non-pulse compression radars, the instrumentation 3 dB bandwidth in MHz should be at least 2/t where t is the pulse width, in microseconds. For a pulse compression system, this bandwidth should be at least 2d/XPW where d is the pulse compression ratio and XPW refers to the expanded pulse width, in microseconds.
30.10 Spectrum analyzers should be calibrated to an amplitude accuracy of 0.5 dB to 1 dB.
30.11 When making measurements involving acquisition of fine grain spectrum details, the instrumentation
3 dB bandwidth in MHz should be less than 1/10t or d/10XPW.
30.12 When making measurement involving recovery of the time waveform of a pulse signal, the instrumentation 3 dB bandwidth in MHz should be greater than 3/t r where tr is the pulse rise time in
microseconds. A measurement objective should be a bandwidth of approximately 10/t r.
22
For Parts Inquires call Parts Hangar, Inc (727) 493-0744
© Copyright 2015 Integrated Publishing, Inc.
A Service Disabled Veteran Owned Small Business