Comtech EF Data XTRT-400C Operation And Installation Manual page 109

Standby Mode
In this mode, there are no faults and the TWT is ready for high voltage to be applied.
Heater Standby Mode
The purpose of the heater standby is to extend the life of the tube when the high
voltage is off.
The temperature of the cathode is the primary determinate of the tube life. The
emission of electrons from the surface of a cathode has a cooling effect on the cathode
surface. Therefore, when high voltage is off the cathode surface temperature increases
shortening the life of the tube. This is a special concern when the amplifier is in standby
mode for extended periods of time, that is, when it is the standby unit.
Heater Standby reduces the heater voltage when the high voltage is off. The
temperature of the cathode is reduced to a temperature slightly below the normal
operating temperature. When high voltage is turned on, it overrides the heater standby
command and returns the heater voltage to its normal setting. When the high voltage is
turned off again the heater voltage is reduced.
When the amplifier has been online and then placed in the heater standby mode, there
is no time delay when the high voltage is turned on.
Note: XTRT series amplifiers always leave the factory with the heater standby mode enabled. In
order to override this factory setting the remote command must be used. See Protocol XTRT Rack
TWTA with LCD chapter 5 for details.
MNC-0400-071
EAR EXPORT CONTROLLED: The information contained in this Manual refers or relates to a product that is subject
to the U.S. Export Administration Regulations (EAR). Transfer of data herein by any means to a Foreign Person,
whether in the U.S. or abroad, may require an export license from the U.S. Department of Commerce.
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Operation
Revision 4