Other Circuits; Port Allocations - Icom IC-F610 Service Manual

4-5 OTHER CIRCUITS

4-5-1 COMPANDER CIRCUIT (MAIN UNIT)
IC-F610 series have compander circuit which can improve S/
N ratio and become wide dynamic range. The circuit is com-
posed in the compander IC (IC14).
(1) IN CASE OF RECEIVING
The demodulated AF signals from the FM IF IC (IC1, pin
9) are applied to the amplifi er section in the compander IC
(IC14, pin 3), and then pass through the low-pass fi lter and
high-pass fi lter sections to suppress unwanted signals. The
fi ltered signals are applied to the expander circuit to expand
AF signals.
The output signals from the compander IC (IC14, pin 38) is
applied to the AF amplifi er circuit after amplifi ed at the ampli-
fi er section.
(2) IN CASE OF TRANSMITTING
The audio signals from the microphone amplifier (FRONT
UNIT; IC2) are applied to the compander IC (IC14, pin 12)
via the D/A converter (IC6, pins 9, 10). The signals are am-
plified at the amplifier section, and are then applied to the
compressor circuit to compress the audio signals. The sig-
nals are pass through the low-pass fi lter and high-pass fi lter
sections and are then applied to the limiter amplifi er section
after being passed through the high-pass fi lter section.
The filtered signals pass through the splatter filter section,
and are then applied to the modulation circuit (D18) via the
PM/FM switch (IC15, pins 1, 6, 7) and D/A converter (IC6,
pins 21, 22).
• COMPANDER IC BLOCK DIAGRAM
RX IN 3
AMP
5
MSK IN
HPF
TX IN
12
AMP
LPF
MSK
BPF
DEMOD
COM-
LPF
PRESSOR

4-6 PORT ALLOCATIONS

4-6-1 OUTPUT EXPANDER (FRONT UNIT; IC1)
Pin Port
number name
KS0–
1–3
KS2
DIM1,
4, 5
DIM2
7 HORN
4-6-2 D/A CONVERTER (MAIN UNIT; IC7)
Pin Port
number name
1–3 T1–T3
4 T4
HPF
AMP
MSK
MOD
HPF
AMP
4 - 5
Description
Output ports for the programmable
function keys (P0–P4, ,
Output LCD backlight control signals.
DIM1 DIM2 LIGHT
HIGH HIGH ON
HIGH LOW OFF
LOW HIGH DIM
LOW LOW OFF
Outputs external device control signal.
High: When matched 2/5 tone sig-
nals are received.
Description
Output the bandpass filters (D4, D8,
D9) tuning signals.
• Outputs the bandpass filter (D10)
tuning signal while receiving.
• O u t p u t s t h e T X p owe r c o n t r o l
signal which selects High, Low1,
Low2 of TX power while trans-
mitting. The output signal is ap-
plied to the APC amplifier (IC2,
pin 1).
38
EXPANDER
AMP
6
LIMIT
LPF
AMP
, , ).
RX OUT
TX OUT