MIL-DTL-25895A
4.2.5 Environmental test data. The antenna shall be subjected to the following test methods of MIL-STD-810.
Performance of the equipment during environmental tests shall be as specified under the electrical tests of 4.2.7.
High temperature
Method 501
Low temperature
Method 502
Temperature shock
Method 503
Humidity
Method 507
Low pressure (altitude)
Method 500
Salt fog
Method 509
Vibration
Method 514
Sand and dust
Method 510
Immersion
Method 512
Temperature-altitude
Method 520 (tailored)
Shock
Method 516
4.2.6 Service condition (special).
4.2.6.1 Mechanical strength. A sample antenna shall be proof tested at a differential pressure of 30 psi applied on
the back side of the cavity. The case shall not rupture nor shall permanent set due to pressure deflection be allowed.
An electrical performance test shall be conducted.
4.2.6.2 Dynamic. An antenna assembly shall be placed in a climate chamber and subjected to 100 cycles of
pressure variation from 30 inches of mercury to 2.0 inches at a rate of approximately 0.5 inch per second. The
percentage of humidity shall be maintained at approximately 90 percent at atmospheric pressure and room
temperature. After cycling, the antenna shall be opened and examined for internal moisture.
4.2.7 Electrical performance. Subsequent to environmental tests specified in 4.2.5 and dynamic test specified in
4.2.6.2, the antenna shall be subjected to the following tests.
4.2.7.1 Voltage standing wave ratio (VSWR). VSWR shall be determined in accordance with best commercial
procedure when the antenna is mounted centrally on and flush with the surface of a circular ground plane not less
than 60 inches radius. Measurements shall be made at 5 MHz intervals from 400 MHz to 480 MHz inclusive. At all
frequencies between 400 and 480 MHz, the VSWR shall be equal to or less than 2.0 to 1. It shall also be determined
that the VSWR is not affected when operating with a differential pressure of 20 psi applied on the back side of the
cavity.
4.2.7.2 Radiation test. The radiation test shall consist of connecting the antenna through a 50-foot length of
RG-21/U cable to a monitored signal source tuned to one frequency within the frequency range of the antenna and
observing the relative level of energy radiated from the antenna as indicated in the output meter of an rf receiving
device tuned to the same frequency as the signal source. The relative level of energy radiated from the antenna shall
not vary more than 10 percent above or below the level of a matched dipole 440 MHz mounted one-quarter wave
length from a reflecting surface or value as supplied by the acquiring activity for this purpose. The dipole shall be
externally matched so as to present the same impedance to the signal source as the antenna.
4.2.7.3 Radiation pattern. The radiation pattern of the antenna assembly shall be measured in accordance with
standard commercial practice to determine compliance with 3.4.4. A circular ground plane of at least 60 inches
radius shall be used.
4.3. Acceptance tests. Acceptance tests shall consist of:
a.
Individual tests (see 4.3.1).
b.
Sampling tests (see 4.3.2).
4.3.1 Individual tests. Each test set shall be subjected to the following tests.
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