Shutdown; Power Control - Tait TB8100 Service Manual

7.1.4

Shutdown

7.1.5

Power Control

118 Power Amplifier Circuit Description
The PA software will prevent transmission under the following conditions:
the following calibration procedures were not completed successfully:
6W driver transistor, 60W final transistor 1 or 60W final
transistor 2 bias
detector bias
supply voltage
output power
the supply voltage drops below 24VDC or exceeds 32VDC
the transmit current of the 6W driver and 60W final transistors does not
reduce to a safe level after foldback
the configuration of the PA is invalid.
The PA has a power control circuit which keeps the output power constant
and protects the PA from VSWR mismatch conditions. The control circuit
monitors forward and reverse power and these measurements are used to:
determine forward and reverse power
keep the output power constant
foldback the power under mismatch conditions
calculate VSWR.
The power level is set by requesting the power level in watts via an I
message. The minimum size of a power step is 1W and the range of output
power settings is:
Model
5W
50W
100W
The forward power, reverse power and load VSWR measurements may also
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be requested via I C bus messages.
The foldback loop is analogue until the VSWR reaches 10:1, at which point
the microprocessor initiates foldback.
The microprocessor and control loop are also used to shape the RF signal
envelope during key-on and key-off transients.
Output Power Range
1W to 5W
5W to 50W
10W to 100W
© Tait Electronics Limited September 2006
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C bus
TB8100 Service Manual