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KA BAND OUTDOOR TWT AMPLIFIER
5.6.1 Post
The microprocessor-based controller performs a list of tests that establish its ability to control and
monitor the amplifier. Some areas covered by POST include checking validity of information in
the battery-backed RAM, EPROM checksum, and other controller specific aspects. During this test
the amplifier will accept no user inputs that affect the beam state.
If there is no POST failure, the amplifier starts the heater time delay cycle (HTD).
If there is a POST failure, the system halts at the failed test and reports the error (FAULT LED
lights).
5.6.2
Heater Time Delay (HTD)
HTD (Heater Time Delay) allows the TWT heater to warm the cathode to its operating point. HTD
is nominally 3 minutes, but can be a shorter period after a prime power failure as follows:
HTD proportional time delay:
•
If time off <5 seconds, no HTD.
•
If 5 seconds<time off<1.5 minutes, HTD = 1.5 x time off.
•
If time off >1.5minutes, HTD = 3 minutes.
Heater Reduce is off during this time.
If the TRANSMIT state is commanded during the HTD cycle, the amplifier will automatically
transition to the TRANSMIT state when the cycle is complete (if there is no fault).
If a fault occurs during HTD, the unit will transition to the Fault state. The HTD countdown clock
continues after a fault occurs.
5.6.3 Standby
State
The STANDBY state is the normal beam-off state. During STANDBY, high voltage is off and the
unit does not amplify the RF input drive signal.
While the unit is in the STANDBY state, the STBY LED is lit. After the beam is off for one minute,
the Heater Reduce command is activated.
CAUTION!
Leaving the amplifier in Standby for more than 4 hours
is not recommended. TWT longevity can be reduced.
D
OC
.01031492 R
EV
.3
5-5