General Precautions for TWTA Operation, Most of these items are
contained in the operation Manuals. However, some may not be obvious:
1.
When an Amplifier has not been used for some time, more than 6 months, the unit
may not produce full power. In this case, operate the Amplifier at about 1/2 of
it's rated power for 12 hours and retest. If power is still not to
specification, the unit will need service.
2. Helix Current: If the
Amplifier trips OFF for Helix Current when RF is applied restart unit without
RF applied; turn on RF at a low level (approx. 10 dB less than rated input)
allowing helix current to stabilize, may take 10 minutes. Gradually increase
input power allowing helix current to stabilize at each level. This is most
important for high power (> 20 Watts) or high frequency (> 18 GHz) units
when they have been in storage for a long time.
3. The longest life for
a TWTA is when the unit is operated near its full RF power output or in
storage.
CAUTION when the unit is turned ON, it should be put to the OPERATE
mode (OPERATE, RF ON, BEAM ON) within a short time. A few minutes is OK but
long periods of STANDBY operation will dramatically shorten the life of the
TWT.
4. TWT Amplifiers should not be operated outside there normal RF
Band, if such operation requires the input drive be increased higher than
normal. The Amplifier may produce good power. However, the high input drive (
low gain ) is likely to damage the Helix.
5. Some TWT's can be damaged
by pulsing the Input RF. The RF pulse caused a momentary high Helix current and
may over time damage the Tube. This problem has shown up when the unit is used
for long term pulse operation
6. Some RF Amplifiers have very high
gain. It is recommended to start with RF input very low, -20dBm or less if you
are not sure of the drive level required.
CAUTION DO NOT ALLOW
AMPLIFIERS TO REMAIN IN STANDBY MODE LONGER THAN 1/2 HOUR.
BE SURE THE RF
INPUT AND OUTPUT PORTS ARE PROPERLY TERMINATED.
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