Receiving Filters Of Rx Fil Board - Furuno FS-1575 Service Manual

The RX FIL board provides the following major functions:
1) Pre-selector and Band-pass filters to reduce interference.
2) Antenna switching circuit between T/R ANT and R. ANT.
3) Divider to divide the receiving antenna line into a Receiver circuit and WR2.
4) The "R. ANT" input level is designed to withstand 30-Vrms RF signal for a period
of five minutes.
5) Interface with the DUP-FIL board (05P0863), but the 05P0862B board does not
connect to the DUP-FIL board.
The DUP FIL board reduces transmission signals for full-duplex communication.

1. Receiving filters of RX FIL board

Receiving filters are switched as shown in the table below according to received
frequency.
Except DSC and NBDP
Band
1 (LPF) 100 to 1449.9 kHz
2 (PRESEL) 1450 to 4999.9 kHz
3 (BPF) 5000 to 7999.9 kHz
4 (BPF) 8000 to 17999.9 kHz
5 (BPF) 18000 to 29999.9 kHz
Note 1)
Any mode other than DSC and NBDP modes
Preselector is used to receive frequencies between 1450 kHz and 4999.9 kHz.
Note 2)
DSC and NBDP modes
LPFs in the band 1 are used up to the band of 5 MHz.
BAND-1: 100 to 1449.9 kHz
CONFIDENTIAL (internal use only)
This confidential document is used only by FURUNO authorized persons.
It is strictly prohibited to reproduce the document in whole or in part without prior written permission of FURUNO.
DSC and NBDP Mode
Modes
100 to 4999.9 kHz
See Note 1)
8000 to 17999.9 kHz
18000 to 29999.9 kHz
0dB
7-38
Table 7.3.1 Switching of Receiving Filters
See Note 2)
5000 to 7999.9 kHz
BAND-3: 5000 to 7999.9 kHz
7.3 Receiver Circuit
Loss (Max.)
4.0 dB
3.1-MHz or more: 4.0 dB
3.0999 MHz or less: 6.0 dB
3.0 dB
4.0 dB
6.0 dB
0dB