MIL-DTL-25707F
Step 14. With antenna de-energized, adjust chamber temperature to step 14 conditions (following steps where a
change in temperature at low pressure is required, pressure may be increased to ambient before changing the
temperature and then returned to the required pressure following temperature stabilization) and maintain.
Antenna temperature shall be stabilized. The antenna shall be energized at the highest specified input
voltage and chamber pressure adjusted to step 14 altitude. The antenna shall be operated four time periods
each of 10-minute duration and shall be followed by a 15-minute period with the antenna de-energized. The
antenna shall be checked for satisfactory operation during each operating period. Thermal sensor readings of
antenna temperature shall be recorded at the beginning and end of each operating time period.
Step 15. Adjust chamber test conditions to standard ambient. After the antenna temperature has stabilized, an
operational and performance check of the antenna shall be made. Results shall be compared with
performance before temperature-altitude test.
4.5.7.2 Shock (see 3.5.3). Method 516 of MIL-STD-810.
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.
4.5.7.3 Vibration (see 3.5.4). Method 514 of MIL-STD-810.
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.
Resonance dwell. The antenna shall be vibrated along each axis at the most severe resonant frequencies
(2)
determined. Dwell time at each resonant frequency shall be 30 minutes (per axis).` If more than four significant
resonant 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 condition. The final resonant
frequency shall be recorded.
Cycling. The antenna shall be vibrated along each axis in accordance with test levels of figure 1. Sinusoidal
(3)
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 1.
The specified sweep time is that of an ascending plus a descending sweep.
4.5.7.4 Humidity (see 3.5.5). Method 507 of MIL-STD-810.
a.
Procedure I.
Ten 24-hours cycles, then operational test at 30°C and 85 percent relative humidity.
b.
c.
Humidity
Temperature
Relative humidity
test cycle
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
Maintain ≥ 85 percent
8 - 24 hours
Gradual decrease to
+30°C (+86°F)
4.5.7.5 Fungus (see 3.5.6). Method 508 of MIL-STD-810. The manufacturer shall certify that all materials are fungus resistant
or perform the test specified in method 508.
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