Motorola DIMETRA MTS 2, Инструкция по установке, настройке и базовому обслуживанию

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Transceiver (XCVR) Chapter 10: Base Radio
Transceiver (XCVR)
The transceiver provides the receive and transmit and control functions for the Base
Radio. The transceiver consist of three elements:
•
Receiver-performs the receive function
•
Exciter-performs the transmit function
•
BR Controller-performs the control function
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
fi
ltering 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 Ampli
fi
er (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
fl
ash 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 con
fi
guration data are contained within the BRC
fl
ash memory. The software
de
fi
nes operating parameters for the BR, such as output power and operating frequency.
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.
Power Amplifier
The Power Ampli
fi
er (PA) in conjunction with the exciter provides the transmitter functions for the
Base Radio. The Power Ampli
fi
er accepts the low-power modulated RF signal from the exciter and
ampli
fi
es 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:
•
350 MHz – 379 MHz
•
380 MHz – 470 MHz
10-6
6802800U74-N September 2009