AR 1000TP8G18 Series, Operating And Service Manual

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Model 1000TP8G18
12 Rev -
CAUTION:
Never operate the TWTA without a matched input termination or drive
source. When operating the unit with an antenna and without adequate
isolation to the input, use caution in selecting well-shielded input cables
and signal source. Use a 6 dB or larger pad (RF attenuator) directly at the
TWTA input connector to reduce risk of “looping” oscillation.
3.2.6 External Interlock Connector
The TWTA is provided with an external interlock capability via a 15-pin female D-sub connector on the
power supply/control module. To enable the high-voltage power supply, it is necessary to provide continuity
between pins 3 and 4. If the amplifier shuts down because the interlock was opened, it will be necessary to
reset the system to return to standby (see
System Shutdown Screen” in section 3.4). There is an internal
jumper between J2 pins 1 and 2; a continuity check through these pins can be used to verify the presence of
the amplifier in the instrumentation system. Users may adopt this interlock feature to disable the RF output
for either equipment protection or as a backup for personnel protection.
CAUTION:
Do not rely on the external interlock for personnel protection. The intent
of the external interlock feature is to disable the RF output for equipment
protection. Use proper operating and safety procedures to ensure that
power is removed for personnel safety.
3.2.7 Video Input (Pulse Gate) Connection
This amplifier is provided with a rear panel BNC connector that is used for pulsing the beam of the TWT and
hence the RF output. There will be RF output only when there is RF input and a simultaneous High Level
video pulse input. A TTL Level video pulse must be provided at the Pulse Gate input connector. High level
(+2 to +5 V pulse) enables the TWTA. Low level (0 to 0.4 V baseline level) disables the TWTA. An open
input is considered a Low level. The Pulse Gate input impedance is 50 ohms nominal.
CAUTION:
Always maintain the Video Pulse parameters at the Pulse Gate input
within the specified TTL levels, Pulse Width, Pulse Rate (PRF) and Duty
Cycle called out on the specification sheet for this amplifier or in this
manual. Failure to comply with the specified TTL levels may result in
modulator failure.
Refer to Amplifier Research Application Note No.35 for additional information on use of pulse only TWT
amplifiers. A copy of this application note is included as an appendix to this manual.