TECHNICAL NOTE – OPERATION OF MT4400 TWTA
08/10/2004
TN4400-3
MCL, INC.
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4.2.1 Filament
Off
This state occurs after a Filament Off command (Remote or Computer) has been issued. In this
state the TWTA logic will be activated along with any power supplies or cooling required to
keep the logic powered on. During this state the HVPS and Filament PS circuits will be shut
down. The HPA cannot be in Transmit when this state is initialized.
4.2.2 Filament
Delay
This state occurs after the HPA is turned on or a Standby command (Remote or Computer) has
been issued when the HPA is in the Filament Off State. During this state all TWTA circuitry
will be activated except the high voltage power supply. At the end of this delay the TWTA will
be in the Standby mode.
4.2.3 Standby
This state occurs after the filament warm-up delay has ended or after a Standby command
(Local, Remote, or Computer) has been issued while the TWTA was in Transmit. During this
state all TWTA circuitry will be activated except the high voltage power supply. The Transmit
and Standby modes are mutually exclusive states.
4.2.4 Transmit
This state occurs after a Transmit command (Local, Remote, or Computer) has been issued
when the TWTA was in the Standby mode. During this state all TWTA circuitry will be
activated including the high voltage power supply. The Transmit and Standby modes are
mutually exclusive states.
4.2.5 Transmit
Selected
There are three ways Transmit Selected can be activated. First, when the HPA was in the
Transmit mode then the HPA has a power failure, and then the HPA power returns. After the
power failure, Transmit selected will be activated during filament delay if no faults are present
during delay. Second, while the HPA is in the Delay or Filament Off mode if the operator were
to press the Transmit button, Transmit Selected mode would be activated and at the end of
filament warm-up delay the HPA will go into Transmit. Third, during a tube fault counter
cycle, Transmit selected is a warning to the operator that the TWTA will automatically go into
Transmit soon. If the Standby function is selected, the Transmit Selected mode will be
canceled. Transmit Selected will be indicated in two ways on the Remote panel during the
proportional delay. First an indication will appear on the front panel vacuum fluorescent
display (VFD), and second, the Transmit LED located on the Transmit button will flash.
