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4-2 TRANSMITTER CIRCUITS

4-2-1 MICROPHONE AMPLIFIER CIRCUIT (MAIN UNIT)

The microphone amplifier circuit amplifies audio signals

from the microphone to a level needed for the modulation
circuit.

While connecting the microphone to ID-1, the AF signals
from the microphone (J1600, pin 6) are applied to the micro-
phone amplifier (Q1673) via the microphone mute switch
(Q1670). The amplified AF signals are applied to the mode
switch (IC1670, pins 1, 6, 7).

While connecting the microphone to RC-24, the AF signals
from the microphone (RC24; J1) are applied to the MAIN
unit (J1600, pin 6) via the buffer amplifier (RC-24; Q13).

• DV MODE

The amplified AF signals from microphone amplifier (Q1673)
are amplified at the ALC amplifier (IC1672, pins 3, 5) via
the mode switch (IC1670, pins 1, 7). The amplified signals
are applied to the IDC amplifier (IC1671, pins 6, 7) and then
passed through the splatter filter (IC1671, pins 1, 3).

The filtered signals are applied to the LOGIC-1 unit via the
J1801 (pin 10).

• FM MODE

The amplified AF signals from microphone amplifier (Q1673)
are passed through the mode switch (IC1670, pins 1, 6)
and then applied to the IDC amplifier (IC1671, pins 6, 7).
The amplified signals are passed through the splatter filter
(IC1671, pins 1, 3) and mode switch (IC1673, pins 1, 6).

The CTCSS signals (CTCS) from the CPU (LOGIC-1 unit;
IC50) via (LOGIC-1 unit; IC57, pin 1) are mixed with the AF
signals from the IDC amplifier (IC1671, pin 7). The mixed
signals are passed through the splatter filter (IC1671, pins 1,
3) and mode switch (IC1673, pins 1, 6).

The switched AF signals (IC1673, pin 6) are applied to the
modulation circuit.

4-2-2 DIGITAL CIRCUITS (LOGIC-1 UNIT)

• DV MODE (VOICE OPERATION)

The AF signals from the splatter filter (MAIN unit; IC1671,
pin 1) are applied to the liner CODEC IC (IC1, pin 24) to
convert into digital voice data at the A/D converter section
as the "DAMOD" signal. The converted digital audio signals
are applied to the AMBE CODEC IC (IC2) for code com-
pression and are then applied to the CPU (IC50).

The digital audio signals are processed at the CPU (IC50)
and then applied to the FPGA IC (IC200).

• DD MODE/DV MODE (LOW SPEED DATA OPERATION)

While operating in DD mode the data signal from connected
PC are applied to the Ethernet controller (IC104) and then
applied to the CPU (IC50)

While operating in DV mode (low speed data operation) the
data signal from connected PC are applied to the USB con-
troller (IC550) and then applied to the CPU (IC50)

The applied data signals to the CPU (IC50) are processed
and then applied to the FPGA IC (IC200).

The output signals from the CPU (IC50) are applied to the
FPGA IC (IC200) to convert to the I/Q baseband signals and
then output from pins 75–80, 82–87, 92–99 (IC200). The I/Q
baseband signals are mixed at the resisters (R250–R293)
and then pass through the baseband filters (IC300, IC301,
IC302).

The filtered signals (I/Q baseband signals) are applied to the
MAIN unit via J400 (pins 1, 3).

4-2-3 MODULATION CIRCUIT (MAIN UNIT)

•

DV/DD MODE

The modulation circuit modulates the 2nd LO signal at the
quadrature modulation circuit (IC890) using the I/Q base-
band signals from the LOGIC-1 unit.

The I/Q baseband signals from the LOGIC-1 unit are ampli-
fied at the I/Q baseband amplifiers (IC832, pins 1, 2, 6,
7) and then applied to amplifier section (pins 4, 7) of the
quadrature modulator IC (IC890, pins 4, 7, 14). The 2nd LO
signal is applied to the quadrature modulator IC (IC890, pin 8)

4 - 4

• MODULATION AND TRANSMIT CIRCUITS

FI1020

FI961

1st mixer

FI880

Q1020

I/Q baseband
signals

“DAMOD” signal to liner CODEC IC
(LOGIC-1 unit; IC1, pin 24)

“MODI” signal to D631

Q1673

Q1670