Transmitter Circuits - Icom IC-F8101 Service Manual

DEMODULATOR CIRCUIT (DSP1-A UNIT)
The 3rd RX IF signal from the 3rd RX IF circuits is passed
through the buffer (IC3602, IC3603), and then applied to the
A/D converter to be converted into digital audio signal.
The converted digital audio signal is applied to the DSP
(IC8201) on the DSP2-A UNIT, and demodulated and pro-
cessed.
• DEMODULATOR AND RX AF CIRCUIT
RL3001 IC3011
Speaker
To the [SP] jack
SW

4-2 TRANSMITTER CIRCUITS

TX AF CIRCUIT (DISPLAY-A and DSP1-A UNITS)
The audio signal from the microphone (MIC signal) is
applied to the DISPLAY-A UNIT, through the MICROPHONE
CONNECTOR (MIC UNIT; J6902), and then applied to the
MIC AMP with ALC circuit (IC6005). The amplified MIC sig-
nal is applied to the DSP1-A UNIT.
The MIC signal from the DISPLAY-A UNIT is amplified by
the AF AMP (IC3004), and then applied to the electronic
volume (IC3008), which adjust the MIC signal in level.
The level-adjusted MIC signal is applied to the modulation
circuits.
• TX AF CIRCUIT
DISPLAY-A
DSP1-A UNIT
UNIT
IC6005
IC3004
MIC
MIC ALC AMP
AMP
MODULATION CIRCUIT (DSP1-A UNIT)
The MIC signal from the TX AF circuits is applied to the
CODEC (IC3611), through the Balance-Unbalance convert-
er (IC3604 and IC3607), to be converted into digital audio
signal.
The converted digital audio signal is applied to the DSP
(IC8201) on the DSP2-A UNIT, and processed and modu-
lated.
The processed signal is applied to the DSP1-A UNIT again,
and converted into analog audio signal by the CODEC
(IC3611), and then applied to the 3rd TX IF circuits on the
MAIN-A UNIT, through the buffer (IC3615), as the 3rd TX IF
signal.
• MODULATION CIRCUIT
DSP2-A
UNIT
IC3604
IC8201
IC3607
IC3611
DSP
From the TX CODEC
BUFF
AF circuits
IC3008 IC3003
I C 3 0 0 5
AF Electronic
AF
LPF
PA
volume MUTE
IC3008
AF GAIN
To the modulation circuits
ADJ
DSP1-A UNIT
IC3615
IC3611
BUFF
CODEC To the 3rd
TX IF circuit
The demodulated signal is applied to the CODEC (IC3611)
to be converted into analog AF signal. The AF signal is
passed through the buffer (IC3615), LPF (IC3003) and AF
mute SW (IC3005), and then applied to the electronic vol-
ume (IC3008), which adjusts the AF output signal in level.
The level-adjusted AF signal is amplified by the AF power
AMP (IC3011), and then output from the connected speak-
er, through the speaker SW (RL3001) and speaker connec-
tor (J3006).
DSP2-A UNIT
IC8201
IC3615 IC3611
DSP
CODEC
BUFF
3RD TX IF CIRCUIT (MAIN-A UNIT)
The 3rd TX IF signal from the modulation circuits is applied
to the 3rd TX IF mixer (IC1402), through the 3rd IF SW
(IC1403), to be mixed with the 3rd TX LO signal, resulting in
the 455 kHz 2nd TX IF signal.
The 2nd TX IF signal is amplified by the 2nd TX IF AMP
(Q1417), passed through the 2nd TX IF filter (FI1402), and
then applied to another 2nd TX IF AMP (Q1416).
The amplified 2nd TX IF signal is applied to the 2nd TX IF
circuits.
• 3RD TX IF CIRCUIT
IC1403
RXIF
From the modulation
circuits
3rd IF SW
4-2
DSP1-A UNIT
IC3608
IC3602,IC3603
36 KHz 3rd RX IF
A/D
BUFF
From the 3rd RX IF circuit
455kHz 2nd TX IF
Q1417
FI1402
IC1402
CERAMIC
D1419
D1421
D1417
IF
BPF
AMP
3rd TX LO signal
Q1416
D1415
IF
To the 2nd TX
AMP
IF circuits