Tait TB9100 Installation And Operation Manual

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Tait TB9100 Installation And Operation Manual Manual pdf 105 page image

TB9100/P25 CG Installation and Operation Manual Technical Description 105© Tait Electronics Limited January 20078.3 PA Module OperationThe TB9100 PA is a modular design with the circuitry divided amongseparate boards which are assembled in different configurations in differentmodels. Interconnect boards are used in certain models to connect boardsthat are physically separated on the heatsink. The 5, 50 and 100W PAs areavailable for operation on 28VDC, while the 5 and 50W PAs are alsoavailable for operation on 12VDC.Figure 8.4 on page 107 shows the configurations of a 100W 28V PA and a50W 12V PA, along with the main inputs and outputs for power, RF andcontrol signals.PAs can only be installed in position 3 or position 5 of the subrack. Referto “Configuring the Subrack Interconnect Board” on page 94 for moreinformation.RF Circuitry The RF output from the reciter is fed first to the 6W driver board. In the100W model the output from the 6W driver board is fed into a –3dBhybrid coupler on a separate splitter board and then to two 60W final boardsin quadrature. The outputs from these two boards are then combined byanother –3dB hybrid coupler on a separate combiner board before being fedto the low-pass filter (LPF)/directional coupler board.In the 50W model, the output from the 6W driver board is fed to one 60Wfinal board and then to the LPF/directional coupler board. In the 5Wmodel, the output from the 6W driver board is fed directly to the LPF/directional coupler board.Control Circuitry The microprocessor located on the control board monitors and controls theoperation of the PA. There are no manual adjustments in the PA because allthe calibration voltages and currents required to control and protect the PAare monitored by the microprocessor. The software also automaticallydetects the PA configuration and controls the PA accordingly.If any of the monitored conditions exceeds its normal range of values, themicroprocessor will generate an alarm and reduce the output power to apreset level (foldback). If the measured values do not return within thenormal range after foldback, the PA will be shut down.The alarms and diagnostic functions are accessed through I 2 C bus messageson the system control bus via the reciter, control panel and CSS. Somemeasurements are logged by the microprocessor and this information canalso be accessed through the system control bus.The operation of the cooling fan mounted on the front panel is determinedby the temperature limits set in the PA software.Power Supply The 100W PA operates off a 28VDC external power supply only, while the5 and 50W PAs can operate off a 28VDC or 12VDC external power supply,