MIL-PRF-1/889J
TABLE I. Group A inspection - Continued.
Conditions
Symbol
Limits
Unit
Inspection
Method
MIL-STD-
1311
min
max
Conformance
inspection, part 3
-continued
hrs
---
100
RF useful output;
t
---
Life test (3)
airflow = 1.5 cfm
---
Life-test (3)
end points:
W
---
200
class c amplifier;
Po
2214
RF useful power
F = 470 to 500 MHz;
output 8/
Eb = 2,000 Vdc; Ec1 -90 Vdc;
Ec2 = 250 to 300 Vdc;
Ic1 = 25 mAdc (max);
Eg1/Ib = 250 mAdc;
Ef = 5.5 Vac
---
---
---
---
1011
Humidity 10/
14 days duration;
Ic1 = -20 μA dc (max) under
post test conditions
°C
225
---
T(anode
1143
Forced cooling 4/
Ec1/Ib = 250 mAdc
core)
Coolant-pressure
0.35
---
---
1155
drop versus coolant
Inch
No voltages
flow (forced air) 5/
H2O
NOTES:
1/
Maximum life may be obtained by adjusting the heater voltage in accordance with the application. The heater voltages
(nominal and derated) shall be maintained within ±5 percent (but not less than 5.4 V ac) when consistent operation and
extended tube life are factors. A table of heater voltage versus frequency is presented as a guide for straight-through amplifier
operation:
F (MHz)
Ef (V ac)
Up to 300
6.00
301 to 400
5.75
401 to 500
5.50
When the TUT is operated at 100 percent of maximum rated anode dissipation at an incoming air temperature of 25°C
2/
maximum, a minimum air flow of 3.8 cubic feet per minute (cfm) at sea level, shall pass through the anode cooler. The static
pressure drop across the TUT and socket (see Drawing 246-JAN 13/) at an airflow of 3.8 cfm is approximately 0.30 inch of
water. The pressure drop varies with the amount of escaping air and with the shape and construction of the air director. This
rating applies at bias voltages less than 100 volts and frequencies less than 500 MHz. Air cooling on the TUT base shall be
increased with increasing negative-grid bias or with increasing frequency, or a combination of both. In all cases of operation, a
socket which provides forced-air cooling of the base shall be used and maximum seal temperature ratings must not be
exceeded. The airflow shall be applied before or simultaneously with electrode voltages, and may be removed simultaneously
with them.
4
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