User's Manual

F32700N25.doc Page 5
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switching the antenna between transmitter and receiver
(TX/RX).
Receiver The receiver is a double-conversion super-heterodyne with a
first intermediate frequency (IF) of 45 MHz and a second IF
frequency of 455 KHz. The receiver consists of band-pass
filters, an RF amplifier, a MMIC mixer, crystal filters, and a
one-chip IF system. The injection synthesizer provides the
first local oscillator signal. Outputs from the receiver include
RSSI and analog audio for the baseband routing circuitry and
modem.
Power Supply Consists of circuitry that derives the various operating voltages
for the RF portion of the fixed radio
F32700N25 Fixed Radio Section Descriptions
The F32700N25 Fixed Radio works in the frequency range of 764-776 MHz RX
and 794-806 TX and requires an antenna connected to the RF port.
This section provides detailed descriptions of each of the sections within the
F32700N25 Fixed Radio. Refer to Appendix A to view the F32700N25 Fixed Radio
Circuit Board Diagram.
Microcontroller
The microcontroller (U30) is a major component of the radio as it manages the
operation of the radio. It also controls the operation of the modem, and provides
transmit time-out protection in the event a fault causes the radio to halt in the transmit
mode. It utilizes a reduced instruction set computer (RISC) architecture which provides
low power operation and a powerful instruction set. Other features include a watchdog
timer, serial universal asynchronous receiver/transmitter (UART), two 8-bit timers, and 2
KB of electrically erasable programmable read only memory (EEPROM) storage.
NOTE: The EEPROM Random Access Memory (RAM) stores the setup data entered
by the technician even if there is a loss of power.
Support circuitry
The support circuitry consists of the following: