Signaling Circuit; Encode/Decode; Compander Circuit - Kenwood NX-800 Service Manual

+B
F401
5A
D401
DET
IC405
DC/DC
IC401
DET

8. Signaling Circuit

8-1. Encode (QT/DQT/DTMF/MSK/2TONE)
Each signaling data signal of QT, DQT, DTMF and MSK is
generated by the DSP circuit, superposed on a modulation
signal and output from IC510. The modulation balance of the
QT/DQT signal is adjusted by the D/A converter (IC712) and
the resulting signal is routed to the modulation input of the
VCO and VCTCXO (X1). The each deviation of the TX QT,
DQT, DTMF and MSK tone is adjusted by changing the out-
put level of the IC510 and the resulting signal is routed to
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/DTMF/2TONE/MSK)
The audio signal is removed from the FM detection signal
sent to the DSP circuit and the resulting signal is decoded.
CIRCUIT DESCRIPTION
Q404
SB SW
F501
2A
SBC
IC403
AVR
Q401
/OVRB
INV
50MC
Q412
50MC SW
33A
IC408
AVR
33A-2
Q416
SW
SBC
33M
IC402
AVR
15M
IC409
AVR
/BINT
33BU
Q411
33BU SW
CN405
IC506
DET
IC407
80T SW
RS-232C Driver
Q408
80R SW
ASIC (Analog)
IC410
DC/DC
Audio circuit
IC404
AVR
ASIC, DSP I/O
Q409
Flash memory
50R SW
ASIC, DSP core
IC406
SRAM, RTC
AVR
IC407
AVR
CPU Reset
Fig. 8

9. Compander Circuit

The term "compander" means compressor and expander.
The compander reduces noise by utilizing a compressor and
an expander. The NX-800 contains DSP (IC502) to perform
this operation. The NX-800 compander can be turned on or
off using the FPU.
NX-800
+B
Final Amp
SB
Audio Amp, Display Block
PA connector
SB
D_Sub 25Pin connector
80C
Internal Option
Display Block
80T
TX circuit
TXC
80R
RX circuit
RXC
150C
Assist, Tune circuit
50C
VCO, Internal Option,
I/O expander, FM IC
50R
RX circuit
RXC
33C
TCXO, PLL
33GPS
Internal Option
23