Other Circuits - Icom IC-FR6000 Service Manual Addendum

IF FILTER/IF AMP CIRCUITS
The 1st IF signal from the 1st mixer (L27, 32, D62) is
amplified by the post AMP (Q63, 64) and 1st stage of IF
AMP (Q7) then fi ltered by crystal fi lter (FI3 or FI4), and then
applied to the IF IC (IC5).
The crystal fi lters (FI3 or FI4) are switched by the "NWC １"
signal from the CPU (IC20) according to the RX mode; Wide
(Middle), Narrow and Digital.
<ANALOG RX>
Being mixed with the 2nd LO, the 1st IF signal is converted
into the 450 kHz 2nd IF signal then detected by the internal
quadrature detector (X3 as a discriminator) to demodulate.
The demodulated AF signals are amplifi ed by the AF AMP
(IC36), and applied to the LINER CODEC (IC8). The AF
signals are converted into the digital signal then processed
by the DSP (IC12) then recovered to the analog audio
signals.
The ceramic fi lters (FI1 or FI2) are switched by the "NWC2"
signal from the CPU (IC20) according to the RX mode; Wide
(Middle), Narrow and Digital.
<DIGITAL RX>
The 450 kHz 2nd IF signal is amplifi ed by IC7 then applied
to the DSP (IC12) via ADC (IC9) and digital demodulated.
The processed digital signal is converted into the analog
audio signal by the LINEAR CODEC (IC8).
AF AMPLIFIER CIRCUITS
The AF signals from the LINEAR CODEC are amplifi ed by
the AF AMP (IC36) and level-adjusted by DAC (IC2), then
applied to IC28 via IC29 to be power-amplifi ed.
SIGNALING (DECODE)
The Continious Tone (CTCSS/DTCS), Single Tone (5-Tone/
DTMF/CW_ID) signals in the demodulated AF signals are
decoded in the DSP (IC8).

5-3 OTHER CIRCUITS

POWER SUPPLY
The power supply is switched by Q57 (ON/OFF). 5V (REF5)
from the regulator (IC30) is passed through L58 to supply to
CPU. The 5V also supplies to other sections of the repeater
via Q41 as "+5V."
8V from the regulator (IC27) are supplies to various circuits,
and also supplies to TX circuits as "T8V" and RX circuits as
"8V."
5V from the regulator (IC39) supplies DSP as "DSP5" and
supplies logic circuits; CPU, DSP, etc. via regulators (IC13,
14, 15).
The regulator "F8V" (IC41) provides the supply for FRONT
UNIT.
COMPANDER
The compander in the DSP (IC12) compresses the
amplitude of MIC signals in TX, and expands in RX to
provide high quality recovered sounds.
LED
DS1 (BUSY), DS2(PWR) and DS3 (TX) indicate the
repeater's status: Power ON, T/RX and Cloning.
5 - 2