Specifications

Table Of Contents
INSTALLATION
Page 22 MRC-565 Packet Data Radio Operations and Maintenance
3.2.2 Power Amplifier (PA)
A single power amplifier board is used to amplify RF output from the CMU board to the final
10,25,50,100 watt configurable power output. A special DC power switch is used to control the
rise and fall times of the RF power output. A duty cycle limiter circuit limits the duty cycle of
the power amplifier to 10%. A temperature sensor is also located on this board for monitoring
the internal temperature of the MRC-565. This temperature reading may be transmitted to the
Host for maintenance purposes.
The 10,25,50,100 watt power amplifier is mounted inside an aluminum enclosure to provide RF
shielding between the CMU and the high power output. This board contains a T/R switch for
half-duplex operation, a harmonic low pass filter, and a dual directional coupler and AGC circuit
for power level control. The coupler measures forward and reverse power. If the VSWR
exceeds 3.0:1, the power amplifier automatically shuts down. The power amplifier’s parameters
are also transmitted to the Host for maintenance purposes. The antenna port of the T/R switch
connects directly to the COAX connector mounted on the MRC-565 front panel. The receive
port of the T/R switch is routed through a low pass filter to the Receiver COAX Connector. A
short COAX cable connects the PA receive port to the CMU receive port.