5.3 Block Description
5-6
5.3 Block Description
5.3.1 Receiver unit
1. RCV (08P3227)
The receiving circuit is comprised of two systems to allow simultaneous reception at
518 kHz and 490 kHz or 4209.5 kHz.
NAVTEX signals received from the antenna are separated into two circuits: BPF, Q1
circuit and BPF Q4 circuit. Q1 circuit is a receiving circuit at 518 kHz and 490 kHz
and the Q4 circuit is a receiving circuit at 4209.5 kHz.
Fig. 5.3.1 Block Diagram of RCV board
Signals received at 518 kHz
Signals received at 518 kHz are inputted into RX1 circuit and converted into FSK
signals of 1700 Hz + 85 Hz at U1 of this circuit. The local oscillator frequency
(516.3 kHz) at U1 is generated by dividing the frequency Y1 (4130.4 kHz) by 8 at
U2.
(518 kHz + 85 Hz) - 516.3 kHz = 1700 Hz + 85 Hz
The FSK signals are converted into 0 or 1 signal at U4 (PLL detection). R60 at U4
adjusts the signals by setting “Adjust Rx Unit” to “On” in “[MENU] -> Initialize1”
so that the duty of U4 output signal (BY signal) is 50 %.
BY signals are converted into RS-485 signals at U2 and sent to the Display unit.
+9V
AVR
+9V
AVR
+5V
AVR
LO SW DC
RF
U9
SW
U7, 8
MOD
Q1
Q4
U6
U6
Q1
Q1
BPF
CR3, 4
Q5
BPF
X’tal
FIL1
X’tal
FIL1
X’tal
DIV
(1/8)
DIV
(1/8)
DIV
(1/8)
Y2
(29.756MHz)
U10
BPF
BPF
MF band
4209.5kHz
518kHz
490kHz
U1
TP1
3719.5kHz
FSK
DEM
FSK
DEM
U2
U3
U4
U5
U1
U1
U2
U2
Y1
Y1
4130.4kHz
3906.4kHz
RX-1 (08-001-3159)
RX-2 (08-001-3159)
RX Local-1
RX Local-2
U2
U2
U7
U8
R60
R75
RX Local-2
RX Local-1
CR5
Test Signal
Test Signal
+12V
+12V
+12V
85Hz
Test OFF
Test Start
518kHz
TD-A/B
490kHz
TD-A/B
FREQ
FREQ
RD-A
RD-B
RD-A
RD-B
490/4209.5kHz
490/4209.5kHz
Q6, C77
+9V
+5V
J1
RCV (08P3227)
C6
Содержание Navtex NX-700-A
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Страница 11: ...Contents 7 Specifications AP1 1 Part List D 1 Contents of Drawings S 0 ...
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Страница 61: ...3 2 NX 700B 3 5 3 2 NX 700B Fig 3 2 1 Front view Fig 3 2 2 Rear view and Side view RECEIVER port GND Terminal ...
Страница 63: ...3 2 NX 700B 3 7 Fig 3 2 5 J2 disconnected Fig 3 2 6 J1 disconnected ...
Страница 67: ...3 4 Antenna unit NX 7H 3 11 Fig 3 4 3 Pre AMP unit Fig 3 4 4 Shield cover of Pre AMP unit removed ...
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