4 - 5
4-3-4 VCO CIRCUIT (MAIN UNIT)
• TX-VCO/CHANNEL 70-VCO (RX) CIRCUITS
The VCO outputs from TX-VCO/CHANNEL 70-VCO (Q18)
are amplified at the buffer amplifiers (Q19 and Q27), and are
applied to the TX/RX switch circuit (D42, D43). The receiver
LO signal is applied to the 1st mixer circuit for CHANNEL 70
(D21, L48, L49) passing through a low-pass filter (L51, L52,
C150–C152), and the transmitter signal is applied to the pre-
drive amplifier (Q28). A portion of the VCO output signal is
re-applied to the PLL IC (IC2, pin 2) via the buffer amplifier
(Q15).
• OTHER CHANNELS-VCO (RX) CIRCUITS
The VCO outputs from OTHER CHANNELS-VCO (Q12) are
amplified at the buffer amplifiers (Q13 and Q23). The receiv-
er LO signal is applied to the 1st mixer circuit for OTHER
CHANNELS (D11, L18, L19) passing through a low-pass fil-
ter (L21, L22, C52–C54). A portion of the VCO output signal
is re-applied to the PLL IC (IC2, pin 2 or pin 19) via the buffer
amplifier (Q19).
4-4 DSC CIRCUITS
4-4-1 DSC MODULATION CIRCUIT
(LOGIC, AF AND MAIN UNITS)
The ATIS signal from the CPU (LOGIC unit; IC1, pin 117) is
applied to the buffer amplifier (AF unit; Q18) as “DSC” sig-
nal. The signal passes through the analog switch (AF unit;
IC7, pin 1), and then applied to IDC amplifier (AF unit; IC8a).
Then, the amplified signal is applied to the transmitter cir-
cuit.
The signalis passed through the splatter filter (AF unit; IC8b)
to suppress unwanted 3 kHz or higher signals. The filtered
signals are then applied to the TX modulation circuit via the
D/A converter IC (MAIN unit; IC15, pins 11, 12) as a DSC
modulation signal “MOD”.
4-5 LOGIC CIRCUITS
4-5-1 MAIN UNIT
• CPU
IC1 is a 8 bit single chip micro-computer, which contains
LCD driver, serial I/O, timer, A/D converter, programmable
I/O, ROM and RAM.
• SYSTEM CLOCK CIRCUIT
X1 is a crystal oscillator, which oscillates 9.8304 MHz sys-
tem clock for the main CPU (IC1).
• RESET CIRCUIT
IC2 is a reset IC, which outputs a reset signal (“LOW” pulse)
to main CPU (IC1, pin 79) when turning transceiver power
ON.
Loop
filter
X2
15.3 MHz
Shift register/
data latch
IC12 (PLL IC)
Prescaler
Phase
detector
Programmable
counter
Programmable
divider
3
4
5
2
8
2
PSTB
PCK
PDATA
30.6 MHz signal
to the FM IF IC
(IC1, pin 2)
Buffer
Buffer
Buffer
Q27
Q15
Q19
to transmitter circuit
to 1st mixer circuit
D42
D43
17
Q16
16
Q18, D39, D40
VCO
• PLL CIRCUIT
Buff.
amp.
IC8
"DSC" signal from the CPU
(LOGIC board; IC1, pin 117)
Q19
analog
switch
IDC
amp.
IC8a
LPF
IC5b
D/A
convertor
IC15
to VCO circuit
• DSC CIRCUIT
Содержание IC-M601
Страница 1: ...VHF MARINE TRANSCEIVER iM601 SERVICE MANUAL ...
Страница 37: ...9 5 LOGIC BOARD TOP VIEW H L CH WX 16 MENU POWER CLR F DISTRESS ENT 0 CE 7 8 9 4 5 6 1 2 3 9 2 ...
Страница 40: ... BOTTOM VIEW MAIN UNIT 8 14 7 1 7 1 8 1 4 8 5 14 9 5 ...
Страница 42: ... BOTTOM VIEW AF UNIT 5 8 4 1 5 8 4 1 GND 4 1 to MAIN unit J5 GND VCC VCC 9 7 ...
Страница 53: ......
Страница 54: ...1 1 32 Kamiminami Hirano ku Osaka 547 0003 Japan S 13908HZ C1 C 2002 Icom Inc ...