TECHNICAL NOTE – OPERATION OF MT4400 TWTA
08/10/2004
TN4400-3
MCL, INC.
33 of 36
5.
Check that the Status LED has a Steady Yellow LED at the end of the 3 minute warm-up
cycle; this indicates a Standby condition.
Never activate transmit unless an RF load is connected to the RF output.
Avoid operating the system in standby for more than 60 minutes; use the
Filament Off control for long periods of Standby. See 46A0009 –
Extending Tube Life Information, included as an appendix to TN4400-5
– Technical Note, Preventative Maintenance for MT4400.
6.
Insure that the RF input to this system is at the desired frequency, and this frequency is
within the TWTA operating frequency band.
7.
Send the Transmit Command (HV On) to activate the high voltage. The “Transmit” Flag
will be set to true.
8.
Send the RF On Command.
9.
Set the exciter output to RF On.
MT4400 Block Up Converter Option: Be sure to allow ample warm up
time before attempting to drive the HPA to rated output power. The HPA
will need some time (beyond the filament warm up delay) to reach
acceptable frequency stability, from 15 to 30 minutes depending on the
starting temperature.
10. Increase the TWT RF Gain until rated RF Forward Power is obtained from the amplifier
system while staying within the TWT current and voltage limitations (consult the
MT4400 test data for the rated output power to be expected). Monitor the output
reflected RF power to insure that the transmission line is reflecting less than 10% of the
output forward power.
11. If the system reaches rated output before reaching maximum gain, it will be necessary to
further reduce the RF output of the exciter.
CAUTION
CAUTION
