MIL-PRF-1/1753C
TABLE I. Testing and inspection - Continued.
12/ The tube shall be mounted in a resonance free jig and vibrated with sinusoidal excitation in each of three
mutually perpendicular planes through the following amplitudes:
20 to 100 Hz
10 G (or 0.1 inch D.A. max)
100 to 500 Hz
3G
Cycling test: The frequency shall vary from 5 to 500 to 5 Hz with approximately logarithmic progression, and
shall require approximately 30 minutes to traverse the range. This constitutes one cycle. The TUT shall be
vibrated for one such cycle in each of the three planes.
Resonance test: Mechanical resonant frequencies of the tube shall be determined during the cycling test.
Vibration test schedule (times shown refer to one axis)
Type
Room temperature
Resonance
30 minutes
Cycling
30 minutes
13/ The frequency range F1 to F3 shall be traversed by a tuning shaft rotation of 5 ± .5 turns.
14/ Operation outside the upper and lower frequency limit is not recommended since permanent tube damage
may result.
15/ CAUTION: It is important when supplying a dc input to the filament of this tube that the heater terminal be
operated negative in polarity with respect to the heater cathode terminal. Failure to observe this precaution may
result in permanent damage to the tube.
16/ The tube shall be mounted such that the high-voltage bushing is covered and the waveguide output is sealed.
The assembly shall be placed in a 5 percent solution of salt and water for a period of 24 hours. At the end of
24 hours the tube shall be removed from the solution, washed with clean water and dried with an air hose.
The tuner knob and upper tuner assembly will be removed so that the tuner surfaces may be inspected for the
presence of water. Upon completion of the inspection (assuming no water was found within the tuner) the tube
shall be reassembled and operated to meet the power output test requirements of conformance inspection,
part 1.
17/ Stability shall be measured in terms of the average number of output pulses missing, expressed as a percentage
of the number of input pulses applied during the period of observation. The missing pulses (MP) due to any
causes, are considered to be missing if the rf energy is less than 70 percent of the normal energy level. The
stability shall be measured when VSWR of 1.5:1 minimum is introduced in the load and the phase is adjusted at
the start of each measurement interval to produce maximum instability. The missing pulse count shall be
performed over a 3-minute test interval.
18/ The spectrum of the tube rf output, while under random vibration, shall be displayed on a spectrum analyzer.
Adjust spectrum analyzer such that all pulses can be seen on the display. The rf bandwidth shall be greater
than the prf. The sweep rate shall be adjusted so that it is in the range of 4 to 10 times 1/prf. The display shall
be set for 2 MHz per division. A reference spectrum shall be photographed at the beginning and end of the
vibration period (a non-vibrating spectrum) to monitor drifts in the transmit frequency and bandwidth. Ten
photographs will be taken at approximately equal intervals throughout the 20-minute vibration period per axis.
An acceptable bandwidth is defined as the 6 dB amplitude bandwidth of the reference spectrum, plus 6 MHz.
No more than 5 percent of the reference spectrum amplitude may be outside the acceptable bandwidth.
Following completion of the random vibration test, the tube shall meet the power output test requirements of
conformance inspection part 1.
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