Rx Board (05P0842): Common Board - Furuno FS-1575 Service Manual

7.3.3 RX Board (05P0842): Common Board

The RX board consists of a receiving RF circuit, IF circuit, and local oscillation circuit.
The RX total gain of the RX board is approximately 50dB or more.
RX board output signal is inputted to the T-CPU board by the 2nd IF signal (36 kHz)
and demodulated there. NB, NR, SQ, and AGC control signals are processed by the
DSP of the T-CPU board.
Note)
If no WR2 board is mounted, the RX board will watch scan upon receiving general
DSC frequency.
ANT RX
L/C
Q2
LPF
J2
30MHz
CR1-4
RX ATT
18MHz RX
J3
1 IF RX H
2 IF RX C
5 UNLOCK RX
6 CLK RX
7 DATA RX
8 ST PLL RX
9 ST DDS RX
10 DDS IOUP RX
11 DDS RESET RX
13 5V
14 5V
17 RX HW VER0
18 RX HW VER1
19 AGC RX
20 RX ATT
R2
3, 4, 12
GND
15, 16
RX Frequency
J3E
1st Lo F1B (J2B)，A1A，F3C
A3E (H3E)
2nd Lo
2nd IF
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.
U7
FL1
BPF
U6
53.964MHz
TP4
AGC RX
U3
18MHz
Q9
Q7
X3
18MHz
UNLOCK RX
ST PLL RX
DATA RX
CLK RX
U1
5V VA
3.3V
0 0
AVR
R2
Fig. 7.3.6 RX Board Block Diagram
Table 7.3.4 Correlation of Frequencies of RX Board
100 kHz to 29999.99 kHz (10 Hz step)
Fc + 53.964 MHz + 1.5 kHz
Fc + 53.964 MHz
Fc + 53.964 MHz
54 MHz
36 kHz
7-45
U6
Q8
Q1
TP2
Q8
IF AGC
TP3
54MHz
54MHz
L/C
U9
U10
396MHz
DDS
BPF
USB: f + 53.964MHz + 1.5kHz
LSB: f + 53.964MHz - 1.5kHz
CW, AM, TLX: f + 53.964MHz
DDS IOUP RX
DATA RX
CLK RX
ST DDS RX
DDS RESET RX
3.3V VD
3.3V VA 1.8V VA
U2 U4
5V VA
1.8V
3.3V
AVR AVR
7.3 Receiver Circuit
TP7
IF RX H
(36kHz)
TP6
IF RX C
(36kHz)
Q10
1.8V VD
U5
1.8V
AVR
RX
05P0842