MIL-DTL-25708F
Step 7: Repeat steps 2 and 3.
Step 8: Return the antenna to standard ambient conditions and stabilize.
Step 9: Operate and inspect the antenna and compare performance with that before test exposure.
Pretest data requirements and failure criteria shall be specified in the equipment specification.
a.
Procedure: Three shocks in each direction applied along three orthogonal axes of the antenna (total of 18
shocks).
b.
Terminal sawtooth pulse, 20 g's peak, 11 ms duration.
c.
Operation not required during test.
Vibration test procedure: The sinusoidal vibration shall be applied along each of three mutually orthogonal
axes of the antenna. The acceleration levels or double amplitudes (see figure 2) shall be maintained at the
antenna mounting points (mounted without vibration isolators). When input vibration is measured at more
than one central point, the control signal shall be the average of all the accelerometers.
(1) Resonance search. Resonant frequencies of the antenna shall be determined by varying the
frequency of applied vibration slowly through the specified range at reduced test levels but with
sufficient amplitude to excite the item. Sinusoidal resonance search may be performed using the test
level and cycling time specified for sinusoidal cycling test, provided the resonance search time is
included in the required cycling time.
(2) Resonance dwell. The antenna shall be vibrated along each axis at the most severe resonant
frequencies determined. Dwell time at each resonance frequency shall be 30 minutes (per axis) If
more than four significant resonance frequencies are found for any one axis, the four most severe
resonant frequencies shall be chosen for dwell test. If a change in resonant frequency occurs during
the test, its time of occurrence shall be recorded and immediately the frequency shall be adjusted to
maintain the peak resonance conditions. The final resonant frequency shall be recorded.
(3) Cycling. The antenna shall be vibrated along each axis in accordance with test levels of figure 2.
Sinusoidal cycling time (per axis) shall be 3 hours less dwell time. Sweep time 5 - 500 - 5 Hz shall be
15 minutes. The frequency of applied vibration shall be swept over the specified range logarithmically
in accordance with figure 2. The specified sweep time is that of an ascending plus a descending
sweep.
a. Procedure I.
Ten 24-hours cycles, then operational test at 30°C and 85 percent relative humidity.
b.
c.
Humidity
test cycle
Temperature
Relative humidity
0 - 2 hours
Gradual increase from
Gradual increase from
ambient to +65°C (+149°F)
uncontrolled to 95 +5, -3 percent
Maintain +65°C (+149°F)
Maintain 95 +5, -3 percent
2 - 8 hours
Gradual decrease to +30°C
Maintain ≥ 85 percent
8 - 24 hours
(+86°F)
Apply the test for a total of ten 24-hours cycles, then operational test at 30°C and 85 percent
relative humidity.
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