Transceiver (Xcvr); Power Amplifier - Motorola DIMETRA MTS 2 Installation, Configuration And Basic Service Manual

Transceiver (XCVR)

Transceiver (XCVR)
The transceiver provides the receive and transmit and control functions for the Base
Radio. The transceiver consist of three elements:
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The receiver incorporates three separate receiver channels for use in diversity reception. The
bias for the LNAs in the Preselectors is supplied by bias circuitry in the receiver. A +7 V dc
voltage is the output on the QMA receive input connectors.
The receiver performs highly selective bandpass filtering and dual down conversion of the
station receive RF signal. A custom receiver IC outputs the baseband information in a digital
data format and sends it to the Base Radio controller.
The exciter in conjunction with the Power Amplifier (PA), provides the modulation and
transmitter functions for the Base Radio.
The transceiver contains the Base Radio Controller (BRC). The BRC serves as the main controller of the Base
Radio. The BRC provides signal processing and operational control for the other Base Radio circuit blocks.
The LEDs on the front panel indicate the status of the Base Radio monitored by the BRC. All LEDs on the
Base Radio front panel normally flash once from red to green upon initial power-up. A RESET button is
provided to allow a manual reset of the BR (by pressing the button for at least two seconds).
The operating software and configuration data are contained within the BRC flash memory. The software
defines operating parameters for the BR, such as output power and operating frequency.
Power Amplifier
The Power Amplifier (PA) in conjunction with the exciter provides the transmitter functions for the
Base Radio. The Power Amplifier accepts the low-power modulated RF signal from the exciter and
amplifies the signal for transmission through the RF output connector.
Three possible PAs are available, two high-power PAs and a low-power PA. High-power
PAs are available on two frequency bands:
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10-6
Receiver-performs the receive function
Exciter-performs the transmit function
BR Controller-performs the control function
In order to protect the key encryption key in use in the infrastructure, it is recommended
that this key is overwritten using the Key Variable Loader (KVL) device (through
the front serial port) prior to shipping for repair.
In order to avoid the risk of causing a high bit error rate to occur, do not use 385.572MHz
and 419.175MHz as receiving frequencies in the Base Radios of the MTS.
350 MHz – 379 MHz
380 MHz – 470 MHz
Chapter 10: Base Radio
6802800U74-N September 2009