MIL-PRF-1-1705 Electron Tube, Magnetron Type 8896

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MIL-PRF-1/1705C

TABLE I. Testing and inspection - Continued.

7/ The maximum air pressure to assure prevention of electrical breakdown in the output coupling shall be 15 psig for voltage standing

wave ratios up to 1.5 with phase shift variable over 360 electrical degrees. The magnetron shall be coupled directly to RG-51/U

waveguide with a UG-52/U choke flange modified so that mounting holes provide clearance for number 8 bolts.

8/ Nominal tuner dial readings shall be determined for frequency code letters A, B, and C. Frequencies corresponding to code letters

shall be as specified herein. Tuner dial readings shall be determined for cods A and C under test condition 2 and for code B under

test condition 3:

Frequency

Code letter designation

F0 = 8,500 MHz

F1 = 8,600 MHz

A (�10 MHz tolerance)

F2 = 8,750 MHz

F3 = 9,000 MHz

F4 = 9,375 MHz

B (�10 MHz tolerance)

F5 = 9,600 MHz

C (�10 MHz tolerance)

F6 = 9,630 MHz

9/ The specified frequency range, F1 to F5, shall be covered by 130 � 8 turns of the tuner shaft. The frequency increases as the shaft

is driven in a counter-clockwise direction as viewed from the waveguide side of the magnetron.

10/ The radio frequency bandwidth and sidelobes shall be within the limits specified when a VSW R of 1.5 minimum is introduced in the

load at a distance of 1 � .0.05 meters from the magnetron flange and phase is adjusted at the start of each measurement to produce

maximum degradation.

11/ 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 a VSW R of 1.5 minimum is

introduced in the load at a distance of 1 � .0.05 meters from the magnetron flange and phase is adjusted at the start of each

measurement to produce maximum instability. The missing pulse count shall be performed over a 3 minute test interval.

12/ After the nonoperational holding period of 168 hours minimum, the anode voltage shall be applied 180 seconds (max) after the

application of the standby heater voltage (Ef). The missing pulse count test interval of 3 minutes shall start immediately after the

application of anode voltage.

13/ For frequency modulation measurements, the maximum peak-to-peak frequency deviation shall not exceed the specification. The

test shall be performed using alternating current (60 to 400 Hz) in the heater at the specified voltage. The test shall be run

excluding thermal drift and pushing effects. The test equipment shall have a bandpass of 10 megaHertz minimum at the 3 dB

points.

14/ Readings taken during and after test shall not deviate more than 25 percent from readings taken before test, except that initial

readings less than 10 percent of the maximum specified limits may increase to no more than 25 percent of the maximum specified

limit.

15/ Temperature measurements shall be made only after thermal equilibrium has been reached.

16/ W ith an air flow at standard atmospheric conditions of 35 cubic feet per minute at a back pressure not to exceed 3 inches of water

directed at the tube, using a duct which fits snugly to the cooling fins, the rise above ambient specified shall not be exceeded.

17/ The tuning mechanism shall operate as specified over the entire frequency range.

18/ The tuning shaft shall be continuously driven at a speed of approximately 1,400 rpm. At the completion of the test, the tube shall

meet the tuning and test condition 2 requirements. The backlash shall not exceed 10 MHz. During the test, the tuning shaft may

not be lubricated. A cycle consists of two complete excursions each in opposite directions through the tuning range of the

magnetron.