AR 1000TP8G18 Series, Operating And Service Manual

Page: 37 / 74

Model 1000TP8G18
Rev - 19
3.6 INITIAL TURN ON AND WARM-UP PROCEDURE
Install the TWTA as discussed in section 3.2. Provide an RF generator to the RF input Type N connector. Set
RF generator level below -50dBm and set desired frequency in specified range. Connect a load suitable for
200 watts continuous operation to the RF output. The load VSWR should be less than 2.0:1 A power meter
and suitable attenuators may be connected to the RF power sample port. The RF sample port calibration
factors on the rear of the unit or on the
Info screen in MENU 2 show the relation between the amplifier output
power and the RF sample port power as a function of frequency.
Connect a TTL level video pulse signal within the specification sheet parameters to the Pulse Gate input
(Video). For test purposes, the following parameters may be set:
•
Pulse Width: 10 Microseconds
•
Pulse Rate: 1 kHz
•
Baseline: 0V
•
Peak level: +4V
•
Video source impedance: 50 ohms or less.
This results in a Duty Cycle (also called duty factor) of 1%. This is within the specified range.
Set keylock to LOCAL.
Switch on the MAIN POWER circuit breaker. The fans will operate. The front panel display will show
several identification messages and then the MENU 1 screen. The third line will indicate that the heater time
delay is active.
Allow the heater warm-up delay to expire. Line three will indicate OFF/READY.
CAUTION:
Do not allow the TWTA to remain in STANDBY for extended periods of
time. If the TWTA will not be used in the OPERATE mode within an
hour, shut the TWTA off. The reason for this precaution is that in the
STANDBY mode, the TWT’s cathode runs very hot since it is not cooled
by electrons boiling off the surface, and small amounts of out-gassing are
not cleaned up by the electron beam. Extended operation in Standby can
result in irreparable damage to TWT!
Push S4 (MORE) four times to go to MENU 5. Verify that the heater voltage and current for the TWT are
near their nominal levels. The values of these parameters at the time the TWTA left the factory are logged on
the test data sheet.
Push the OPERATE push-button. You will now see the cathode and the collector voltages rise. Verify that the
grid, collector, and cathode voltages are near nominal. The helix current should be near the nominal value for
no RF drive. Then push MORE or EXIT to go back to MENU 1.
Set the TWTA gain to maximum. Adjust the RF generator to slowly increase the RF drive toward
0 dBm to reach the desired FWD peak power on the display and power meter (connected to sample port). The
forward power reading will become active and reach a maximum reading when peak power output is
achieved. Best performance is obtained when the input RF drive is set at or just below the level that causes the
highest level of peak power output. Do not set input drive above 0 dBm (Input drive above +13 dBm may