MIL-PRF-1/1755B
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 quality 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 me
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 nonvibrating 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 quality conformance inspection part 1.
19/ The tube shall be mounted such that the high-voltage bushing is shielded and the waveguide output is connected to a length of
waveguide. The mounting plate shall have a thermal mass equal to 5 pounds of aluminum.
The tube shall be operated until thermal equilibrium is reached and the body temperature is at least 90șC. All power and cooling
shall be removed. After a period of no greater than 2 minutes, the tube shall be immersed in water at 4șC and left for a period of
3 minutes. This test shall be repeated 3 times. During immersion water shall not be allowed to enter the waveguide nor touch
the high-voltage bushing.
20/ The vibration amplitude shall be 0.0125 g2/Hz, 10 Hz to 2 kHz. The maximum number of missing pulsed shall be 0.25 percent
when measured as stated in note 17, except the load shall be matched.
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