MIL-PRF-1/302P
NOTES:
1.
Forced-air cooling shall be provided for the base and anode. The maximum seal and anode core temperature ratings
shall not be exceeded. At an anode dissipation of 250 watts and an incoming air temperature of 25°C maximum, a
minimum airflow of 5.6 cfm at sea level shall pass through the anode cooler. W ith no voltages applied to the tube, the
static pressure drop across the anode cooler with airflow of 5.6 cfm, at 25°C sea level, is 0.32 inch of water maximum.
The pressure drop varies with the amount of escaping air and with the shape and construction of air director. This airflow
requirement applies at bias voltages less than 100 volts and at frequencies less than 500 MHz (CW ) and 1,500 MHz
(pulsed). Air cooling on the tube shall be increased with increased negative grid bias, increased incoming air temperature,
or increased frequency of operation. The stem shall be cooled either by a portion of the anode air or by a separate air
supply. The airflow shall be applied before or simultaneously with them.
2.
The transit-time heating effect of the cathode shall be compensated by a reduction in heater voltage after dynamic
operation of the tube has started. The back heating is a function of frequency, grid current, grid bias, and duty cycle. For
satisfactory life the heater voltage shall be adjusted to the value indicated below. The rated variation of ±5 percent Ef
shall apply to the value selected from this table. Conditions of operation are limited to those which indicate a heater
voltage of 2.3 volts or more.
FREQUENCY (MHz)
Ef (V ac)
Up to 400
2.5
401 to 1,000
2.2
1,000 to 1,500
2.0
3.
In all electrical tests involving application of heater voltage, forced-air cooling of the tube shall be allowable at the rate of
6.0 cfm, maximum for the base and anode. A separate source shall be used for the base and anode but neither shall
exceed 6.0 cfm. The cooling air shall not have a temperature less than 20°C, nor an absolute pressure greater than
32 in. Hg.
4.
With a prr of 1,000 or less and a tp of 5 µs or less, ib shall be limited to 6.0 amperes. For pulses of longer duration or
higher repetition rates, ib shall be reduced in accordance with the data contained on figure 2.
5.
Use cavity and circuit as shown on Drawing 224-JAN.
6.
This test shall be made 30 minutes after Ef is turned off. Rated airflow shall be maintained during the 30-minute interval.
Measurement to be made with General Radio Megometer No. 1862C, or equivalent. Unused elements are to be left
floating.
7.
This test shall be performed yearly. An accept on zero defect sampling plan shall be used, with sample of three tubes with
an acceptance number of zero defects. In the event of failure, the test will be made as a part of conformance inspection,
part 2 with acceptance level 6.5 (see note 10). The regular yearly sampling plan may be reinstated after three
consecutive samples have been accepted.
8.
Reclaimed materials shall be utilized to the maximum extent possible.
9.
The tube manufacturer warrants the tube for one year from the date of shipment, or 750 hours of heater on time,
whichever first elapses. This warranty applies only when the tube is operated within the maximum ratings (see "Absolute
Ratings" of MIL-PRF-1). A defective tube shall either be replaced, or at the option of the manufacturer, a credit shall be
made in the amount of the original purchase price pro-rated on the basis of 750 hours of heater on-time.
10.
This specification sheet uses accept on zero defect sampling plan, in accordance with MIL-PRF-1, table III.
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