MTR3000 Radio Frequency Distribution System (RFDS) Equipment: Basic Troubleshooting 9-9
9.3.4 Duplexer
The duplexer module allows a transmit and receive channel pair to share a common Tx/Rx antenna.
Each duplexer module consists of six resonant cavities (three for transmit and three for receive)
contained in a temperature-compensated copper enclosure designed to mount in a standard EIA
48.26 cm (19") equipment rack. Each set of three cavities is designed and tuned to pass the
respective transmit or receive channel frequency (or bandwidths) while providing maximum Tx noise
suppression at the Rx frequency and maximum Rx isolation at the Tx frequency.
9.4 Basic Troubleshooting
9.4.1 Replacement Procedure
9.4.1.1 Base Station/Repeater Preselectors
1. Wear an electrostatic discharge (ESD) strap and connect its cable to a verified good ground.
This strap must be worn throughout this procedure to prevent ESD damage to any components.
2. Turn off the DC breaker, and/or pull the AC source power cord from the back of the base
station/repeater.
3. Remove the base station/repeater preselector from the base station/repeater, as follows:
a. Remove the two screws which secure the base station/repeater preselector to the flange of
the base station/repeater using a Torque Driver T30 bit.
b. Label and disconnect the left and right coaxial cable mini-U connection (Male type) from the
front of the base station/repeater preselector.
4. Install the base station/repeater preselect to the base station/repeater, as follows:
a. Secure the preselector housing to the base station/repeater flange using the two screws
which were previously removed.
b. Reconnect the left and right coaxial cable mini-U connection (Male type) to the base station/
repeater preselector.
9.4.1.2 Duplexer
1. Wear an electrostatic discharge (ESD) wrist strap and connect its cable to a verified good
ground. This strap must be worn throughout this procedure to prevent ESD damage to any
components.
2. Disable the channel that is using the base station/repeater in the system with the duplexer
module which will be replaced.
Note
For the correct procedure in handling static-sensitive parts, refer to Section 14.4 on page
14-3.
Note
The base station/repeater preselector can be replaced without shutting the power down.
The base station/repeater needs to be taken out of service in
order to carry out performance testing procedures. Unless the
base station/repeater is already out of service, it is
recommended to perform the procedures during off-peak
hours in order to minimize disruption of service to the system
subscribers.
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