Icom IC-F43TR, Руководство по обслуживанию

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4 - 5
4-5 OTHER CIRCUITS
4-5-1 COMPOUNDER CIRCUIT (MAIN UNIT)
IC-F43TR have compounder circuit which can improve S/N
ratio and become wide dynamic range to suppress the
transmitting signal and to extend receiving signal. The circuit
is composed of 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 amplifier (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 amplified at limiter amplifier section
after being passed through the high-pass filter. The ampli-
fied signals pass through the low-pass filter section, and are
then applied to the modulation circuit (D12) via the FM/PM
switch (IC13), low-pass filter (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 of base band IC (IC14, pin 23), and
then pass through the low-pass and high-pass filter 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 amplifier section (IC14, pins
19, 20), and are then applied to the AF amplifier 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
• BASE BAND IC BLOCK DIAGRAM
4-6 PORT ALLOCATIONS
4-6-1 D/A CONVERTOR IC (IC12)
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