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5 - 5
5-5 OTHER CIRCUITS
5-5-1 COMPANDER CIRCUIT (MAIN UNIT)
IC-F43GT/GS/F44GT/GS have compander circuit which can
improve S/N ratio and become wide dynamic range. The
circuit is composed in the base band IC (IC14).
(1) IN CASE OF TRANSMITTING
The audio signals from the microphone are applied to the
base band IC (IC14, pin 3) via microphone amplifi er (IC23).
The signals are amplified at the amplifier section, and are
then applied to the compressor circuit to compress the audio
signals. The signals pass through (or bypass) scrambler
section, and are then applied to the limiter section after
being passed through the high-pass fi lter. The fi ltered signals
pass through the splatter fi lter section, and are then applied
to the modulation circuit (D12) via the FM/PM switch (IC13),
low-pass fi lter (IC6) and D/A converter (IC12).
(2) IN CASE OF RECEIVING
The demodulated AF signals from the IF IC are applied to
the amplifier section in base band IC (IC14, pin 23), and
then pass through the low-pass and high-pass fi lter section
to suppress unwanted signals. The filtered signals pass
through (or bypass) scrambler section, and are then applied
to the expander circuit to expand AF signals. The signals are
applied to the base band IC’s amplifi er section (IC14, pins
19, 20), and are then applied to the AF amplifi er circuit.
Scrambler/
De-scrambler
TX/RX
HPF
Pre-
emphasis
Limiter
Splatter
VR2
Expander
VR4
RXA2
SMF
De-
emphasis
Com-
pressor
VR1
(HPF)
RX
LPF
VR3
(HPF)
4
TXINO
7 MOD
18
19
20 SIGNAL
3
TXIN
22
RXINO
23
RXIN
21
SDEC
10
14
MDIR
9
MTDT
MTCK
13
MSCK
11
MDIO
12
MRDF
MSK
Modulator
MSK
Demodulator
MSK
BPF
Control
Register
TXA1
RXA1
10
14
15
22
23
BAL
TLVA
RLVA
T1
T2
Outputs the modulation balance level
control signal. The signal is applied to
the buffer amplifier (IC24, pin 1).
Outputs the TX VCO lock voltage con-
trol signal.
Outputs the RX VCO lock voltage con-
trol signal.
Outputs the bandpass filter tuning sig-
nal. The output signal is applied to the
bandpass filters (D19, D20, D24,
D25).
• Outputs the bandpass filter tuning
signal. The output signal is applied to
the bandpass filters (D14, D15).
• Outputs the TX power control signal.
The output signal is applied to the
APC amplifier (IC16, pin 1).
Pin
Port
Description
number
name
• BASEBAND IC BLOCK DIAGRAM
5-6 PORT ALLOCATIONS
5-6-1 D/A CONVERTOR IC (IC12)