Furuno FS-1503, Service Manual

Page: 20 / 136

2-13
2.3 Oscillator
Taking J3E as an example, the outline of the frequency conversion is shown in Figure 2-6
and the relation between the transmitting and receiving frequencies and local frequencies
is shown in Table 2-6.
The frequency conversion circuit and the local oscillator circuit are included in TX/RX
board.
Outline of frequency conversion on J3E
1Lo
(F + 54.455 MHz + 1.5 kHz) 2Lo
(54 MHz) 3Lo
(456.5 kHz)
T/RX
(Fo + 1.5 kHz) AF
(1.5 kHz)
54.455 MHz
455 kHz
DDS PLL 1
1/2
PLL 3
1/100
36MHz
Ref. OSC
1 Lo
2 Lo
3 Lo
Ref.
Figure 2-6 Frequency Conversion
Table 2-5 Frequency of Local oscillator
Mode 1st Local oscillator (1Lo)
2nd Local oscillator
(2Lo)
3rd Local oscillator
(3Lo)
USB F + 54.455 MHz + 1.5 kHz 54 MHz 456.5 kHz
LSB F + 54.455 MHz - 1.5 kHz 54 MHz 453.5 kHz
TX F + 54.455 MHz + 1.5 kHz 54 MHz TX 456.5 kHz
H3E
RX
F + 54.455 MHz
±
0 kHz
54 MHz RX 455 kHz
TLX
F + 54.455 MHz
±
0 kHz
54 MHz 456.7 kHz
FAX
F + 54.455 MHz
±
0 kHz
54 MHz 456.7 kHz