Icom IC-F40GT Service Manual page 10

4-4 FFSK CIRCUIT DESCRIPTION
4-5-1 GENERAL
IC9 is the compounder IC which is controlled by serial data
bus line ("TRD", "MSKE", "DIN", "SCK", "APST", "REGS1",
"REGS2", "RTM", "RDT", "FCLR" signals) from the CPU.
The IC is composed of FFSK transmitting and receiving cir-
cuits, data register circuits, transmitting and receiving data
buffer circuits, and so on.
X4 is oscillated 3.58 MHz reference signal to the IC9.
4-4-2 DECODEING CIRCUIT
The input signal from the FM IC (IC3, pin 9) via the "DSIN"
signal is applied to the compounder IC (IC9, pin 5), and is
then detected bit synchronization detection within 16 bit.
4-4-3 ENCODEING CIRCUIT
The FFSK signal is made by serial data bus line signals, and
is then output from the compounder IC (IC9, pin 6).
• Compounder IC block diagram
RXIN
MSKIN
HPF
5
SERIAL DATA LINE
25, REGS1
30, TRD
29, MSKE 26, REGS2
31, RTM
23, DIN
32, RDT
22, SCK
33, FCLR
22, APST
AMP LPF
3
MSK
BPF
DEMOD
COMPRE-
AMP
SSOR
12
MICIN
In case of the FFSK signal is used for the PM modulation,
the FM/PM switch (IC26) is changed to pin 6.
In case of the FFSK signal is used for the FM modulation,
the FM/PM switch (IC26) is changed to pin 7.
The output signal from IC26, pin 1 is applied to the the buffer
amplifier (IC8, pins 1, 4), and is applied to the D/A convertor
IC (IC13, pins 21, 22). The signal is applied to the modula-
tion circuit (Q12, D7, D8).
HPF
AMP
MSK
LPF
MOD
TXFO
9
BUFF
Q47
2SC4081
27
28
MCIN
X4
CR-563
3.58 MHz
4 - 4
COMPANDER
IC9 TC35453F
AMP
EXPAN-
DER
LPF
HPF
B
IDCIN
LIMIT
AMP
AMP
8
MCOT
1
RXFO
6
TXOUT