Rx Af Circuits - Icom IC-2730A Service Manual

RX AF CIRCUITS

• Left band
The demodulated AF signal from the AF SW (IC119) is
passed through the AF mute SW (IC111, pins 4, 3) and AF fi l-
ter (Q113), and then applied to the volume IC (IC110, pin 4),
which adjusts the AF signal in level.
The level-adjusted AF signal from the volume IC (IC110,
pin 11) is passed through the AF SW (IC109, pins 2, 1), which
selects the AF signal from Left and Right bands.
• Right band
The demodulated AF signal from the AF SW (IC119) is
passed through the AF mute SW (IC111, pins 8, 9) and AF
fi lter (Q112), and then applied to the volume IC (IC110, pin 3),
which adjusts the AF signal in level.
The level-adjusted AF signal from the volume IC (IC110,
pin 12) is passed through the AF SW (IC109, pins 3, 4), which
selects the AF signal from Left and Right bands.
• RX AF CIRCUITS
J101
SP1
J102
IC105 Q104 Q105
AF SP
SP
AMP
MUTE MUTE
IC109
AFSW
Q106
IC106
AF
SP
AMP
MUTE
IC107
BTAF
Optional module
BUFF
When output from [EXTERNAL SPEAKER JACK1]
The output signal from the AF SW (IC109) is passed through
the AF MUTE SW (Q104 and Q105), and applied to the AF
AMP (IC105, pin 1).
The amplifi ed AF signal is applied to the internal speaker
(CHASSIS: SP1) or an external speaker, through [EXTER-
NAL SPEAKER JACK1] (J101).
When output from [EXTERNAL SPEAKER JACK2]
The output signal from the AF SW (IC109) is passed through
the AF MUTE SW (Q106), and applied to the AF AMP (IC106,
pin 1).
The amplifi ed AF signal is applied to [EXTERNAL SPEAKER
JACK2] (J102).
IC103
TX AF circuit
Modulation circuit
LPF
IC104
RPT
SW
Q112,Q139
AF
IC110
FIL
ELEC.
VR
Q113,Q140
AF
FIL
4-4
IC103
BUFF
IC103
BUFF
IC111
2nd IF circuit (Left band )
DETMUTE
2nd IF circuit (Right band )
L_RMUTE R_RMUTE