Furuno FAX-30 Service Manual page 14

RCV board (08P3219)
Three bandpass filters, FL1, FL2 and FL3 locate at the first stage of the receiver. The filter
passes the following frequencies. When receiving NAVTEX message, FL3 is used.
FL1: 2 MHz to 13.2 MHz
FL2: 13.2 MHz to 25 MHz
FL3: 80 kHz to 518 kHz
The shift register, U10 receives three signals, RCV DATA, RCV CLK and RCV BAND from
MAIN board to select the filter. The signal passed through the filter is sent to the first mixer, Q5
and Q6.
The first mixer mixes RF signal with the first local oscillator signal, F+53.98371 MHz and
outputs the first IF signal, 53.98371 MHz. Further, the signal is mixed with the second local
oscillator signal, 54000 kHz at the second mixer, U4. The 16.29 kHz second IF signal is sent to
MAIN board.
Fig.5 Block Diagram of RCV Board
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Chapter 2 Circuit Description