(b)
The antenna unit consists of the antenna pedestal and the antenna planar array. The pedestal itself contains power supply, motor driver, receiver/monitor driver, incremental and zero monitors, and scan and elevation stepper motors.
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737-300/400/500MAINTENANCE MANUAL
(c)
The flat plate develops the required pencil beam radiation pattern by means of phase reinforcement/cancellation of energy from adjacent slots in the planar array.
(d)
The motor driver provides an interface with the power supply to pass the binary encoded scan and elevation drive signals from the R/T to the receiver/monitor driver, and the scan and elevation monitor signals from the receiver/monitor driver to the system R/T. The receiver/monitor driver buffers and translates the binary encoded scan and elevation drive signals to provide motor positioning control signals to the motor driver. It also buffers the incremental and zero monitor signals and provides a binary encoded output to the R/T for interpretation. When commanded by the receiver/monitor driver, the motor driver provides drive voltages to incrementally rotate the scan and elevation stepper motors to move the antenna |90 degrees in scan and |40 degrees in elevation in 0.25-degree steps.
(e)
Incremental monitors track the motor shaft rotation of the scan and elevation stepper motors from a zero reference point to provide constant monitoring for use by the system receiver-transmitter.
(f)
Zero monitors provide a reference synchronizing point for the scan and elevation stepper motors from which incremental changes in antenna position can be measured by the incremental monitors.
(g)
Scan and elevation toggle switches provide a manual means of disabling the input power to the scan and elevation stepper motors. When the pedestal cover is closed, the switches are tripped to ON position by the cover. This prevents the switches from being inadvertently left in OFF position and disabling the antenna drive.
(5) BEJ 061-112; Receiver/Transmitter Functions (Fig. 4)
(a) The R-T unit is a lightweight airborne unit consisting of transmitter, receiver, video processing circuitry, a central processing unit (CPU), input/output circuits, system monitoring circuitry, and power supply.
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