Kenwood NX-300S Service Manual page 16

NX-300(S)
F900
2.5A
IC902
/SAVE
AVR
/5TC
5RC
IC903
SBC
AVR IC
Q901
SB3 SW
CN900
CN404
IC411
5UC
AVR IC
Q403
SBC
SB2 SW
IC708
AVR IC
IC416
AVR IC
IC407
DC/DC
IC414
Detect
SB1
VOL SW
Q408
AND
D408
OR
Fig. 8 Power supply circuit
16
CIRCUIT DESCRIPTION
TX-RX unit (X57)
+B RF Final AMP
APC
50C
VCO
50T
Q905
TX circuit
50T SW
50R
Q902
RX circuit
50R SW
50IF
Q903
IF circuit
50IF SW
33C
PLL, VCTCXO
SB3
TX/Busy LED
150C
IC901
Assist, Tune
DC/DC
Control unit (X53)
50U
Universal
SB2
BackLight
Key Light
5A
Option
31BU
Q409
SRAM, RTC
31BU
33M ASIC, DSP I/O,
IC404
Flach
AVR
15M
IC717
ASIC, DSP core
DC/DC
33A ASIC Analog,
IC406
Audio
AVR
/PSW
Q402 IC108
Lvl Conv ASIC
/BINT
Q401
Lvl Conv
D412
SBC
OR
8. Signaling Circuit
8-1. Encode (QT/DQT/LTR/DTMF/2-tone/MSK)
Each signaling data signal of QT, DQT, LTR, DTMF,
2-tone and MSK is generated by the DSP circuit, super-
posed on a modulation signal and output from IC108. The
modulation balance of the QT/DQT/LTR signal is adjusted by
the D/A converter (IC703) and the resulting signal is routed
to the modulation input of the VCO and VCXO (X500). Each
deviation of the TX QT, DQT, LTR, DTMF, 2-tone and MSK
tone is adjusted by changing the output level of IC108 and
the resulting signal is routed to the VCO and VCXO. The RX
DTMF tone is routed to the receive audio signal system, and
is output from the speaker.
8-2. Decode (QT/DQT/LTR/DTMF/2-tone/MSK)
The audio signal is removed from the FM detection signal
sent to the DSP circuit and the resulting signal is decoded.
9. Compander Circuit
The term "compander" means compressor and expander.
The compander reduces noise by utilizing a compressor
and an expander. The transceiver contains a DSP (IC102) to
perform this operation. The transceiver compander can be
turned on or off using the FPU.