MIL-DTL-28839B
4.6.2 Voltage standing wave ratio (VSWR, see 3.5). The VSWR of the waveguide shall be measured over the
specified frequency range (see 3.1), using the test set up of figure 1. The test equipment shall be capable of
providing a continuous measurement of VSWR over the required frequency range. A means shall be provided for
producing a permanent record of the waveguides' VSWR versus frequency. The permanent record shall indicate the
worst case VSWR numerically and shall provide the calculation used to obtain the calculated VSWR. The
measurement system and permanent record shall provide a minimum accuracy of .03 in VSWR. Other test methods
of equal accuracy may be used.
4.6.3 Attenuation (see 3.6). The attenuation of the waveguide shall be measured over the specified frequency
range (see 3.1), using the test set-up of figure 2. The test equipment shall be capable of providing a continuous
measurement of attenuation over the required frequency range. A means shall be provided to produce a permanent
record of the waveguide's attenuation versus frequency. The measurement system and permanent record shall
provide a minimum accuracy of .01 dB for the frequency range of 2.60 thru 26.5 GHZ and .02 dB for frequency
ranges of .32 through 2.60 GHZ and 26.5 through 90 GHZ. The zero trace is formed by a measurement of the
adapters back-to-back (the normalizer could then subtract this attenuation. Other test methods of equal accuracy
may be used.
4.6.4 Pressurization (see 3.7). The waveguide shall be subjected to the internal air pressure in pound-force per
2
square foot (lbf/ft ) specified (see 3.1). The pressurization supply shall be disconnected and pressure maintained in
the waveguide for 4 hours. At the end of the 4-hour period, the waveguide pressure shall not have dropped more
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4.6.5 Bending radius (see 3.8). One end of the waveguide shall be fixed to a stationary platform with the
waveguide supported in a horizontal position. The free end of the waveguide shall then be bent around a circular
mandrel with the specified radius (see 3.1), to at least a 180-degree bend. A representative sample of the same PIN
as the waveguide under test may be used for this test. The length of the representative sample shall be sufficient to
complete the 180-degree bend. After completion of the bend, the VSWR shall be measured as specified in 4.6.2.
4.6.6 Arial twist (see 3.9). One end of the waveguide shall be fastened to a stationary platform with the waveguide
supported in a horizontal position. To prevent the waveguide from bending, a rigid shaft shall be extended through
the waveguide and fastened to the stationary platform. The free end of the waveguide shall be twisted through a 90-
degree angle. The length of the twisted section shall be as specified (see 3.1). A representative sample of the same
PIN as the waveguide under test may be used for the axial twist test. The length of the representative sample shall
be sufficient to complete the 90-degree twist. After completion of the twist, the VSWR shall be measured as specified
in 4.6.2.
4.6.7 Vibration, high frequency (see 3.10). Waveguides shall be tested in accordance with method 204,
MIL-STD-202. The following details shall apply:
a. Mounting: Unless otherwise specified (see 3.1), rigidly mounted to an appropriate non-resonant
mounting table.
b. Electrical load: Not applicable.
c. Test condition letter: A.
d. Resonance: Not applicable.
e. Measurements after vibration: VSWR and attenuation shall be measured as specified in 4.6.2 and
4.6.3, respectively.
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