Comtech EF Data XTRT-400C Operation And Installation Manual page 80

Figure 21 - Setting and Adjusting Constant Power
Constant Power Mode
Constant Power Mode is an Amplifier function designed to maintain a constant RF
output power (at the RF output flange) adjusting the internal attenuator for changes in
input drive and Amplifier overall gain. Assuming the attenuator has enough dynamic
range and the TWT is not at maximum power the RF output power will be continuously
monitored and adjusted for any changes. This function can be adjusted in a variety of
modes:
1. Configuring while in the High Voltage OFF state – Target RF power at value is
adjusted as shown in above Figure 18. Constant Power Mode can then be
enabled. When High Voltage is enabled, RF is in the enabled state and a proper
RF signal is applied the attenuator will adjust to achieve and maintain the RF
output power selected.
2. Configuring with High Voltage On and RF drive applied – Typically Constant
Power Mode will be initiated while in Transmit mode. In this mode the desired
RF output power has been achieved and the Constant power mode is used to
"lock" in the desired output power. When the desired output has been
achieved simply touch the Constant Power mode select and the mode will be
enabled. Should the desired output power need to be changed touch the
button as shown above and use the knob to change the desired target.
CAUTION - Maximum Constant power setting should not exceed amplifier rated power out
minus 0.5 db. Due to variations in output power across the frequency band it is possible to
cause overdrive mode if the constant power is set too close to saturation.
The amplifier will not allow constant power settings this close to saturated power out.
MNC-0400-071
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Operation
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