Motorola MTR2000 T5544 Instruction / Field Service Manual page 174

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DESCRIPTION
The Models CLN1224, CLN1225 Power Amplifier Modules are described in this section. A general description,
identification of inputs/outputs, functional block diagram, and functional theory of operation are provided. The
information provided is sufficient to give service personnel a functional understanding of the module, allowing
maintenance and troubleshooting to the module level. (Refer also to the Troubleshooting section of this manual
for detailed troubleshooting procedures for all modules in the station.)
General Description
Overview of Circuitry
Motorola Inc., 2006
All Rights Reserved
Printed in U.S.A.
MODELS CLN1224 (132 to 154 MHz), 100W
The Power Amplifier Module (PA) accepts a low-level modulated RF sig-
nal from the Exciter Module and amplifies the signal for transmission via
the site transmit antenna. The output power is continually monitored and
regulated by a feedback and control loop, with a power output control
voltage being generated by the transmitter control circuitry located on the
PA Input/Output boards.
The PA contains the following circuitry:
• Final Device Module – a three stage amplifier which accepts output
from the Exciter Module and provides final amplification up to 135 W.
All the RF amplification transistors are included in this module
• Directional Coupler/Power Detector/Low Pass Filter – couples am-
plified RF signal to transmit antenna connector; also generates dc volt-
ages proportional to forward and reflected power for use in TX power
control loop; provides harmonic suppression for the station
• Single Circulator – provides isolation between Power Amplifier out-
put and transmit antenna
• Temperature Sense Circuitry – provides variable resistance signal pro-
portional to heat sink temperature; signal is monitored by the PA
power control circuitry
Government & Enterprise Mobility Solutions
1301 E. Algonquin Road, Schaumburg, IL 60196
POWER AMPLIFIER
CLN1225 (150 to 174 MHz), 100W
MODULE
68P81096E24-C
06/30/06-UP