Kenwood NX-800H Service Manual page 22

NX-800/800H
+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
output level of the IC510 and the resulting signal is routed
to VCO and VCXO. The RX DTMF tone is routed to the re-
ceive 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 de-
coded.
22
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
15M
IC409
AVR
33M
IC402
AVR
33BU
Q411
/BINT
33BU SW
CN405
IC506
DET
Q407
80T SW
RS-232C Driver
Q408
80R SW
ASIC (Analog)
IC410
DC/DC
Audio circuit
IC404
AVR
ASIC, DSP core
Q409
ASIC, DSP I/O
50R SW
Flash memory
SRAM, RTC
IC406
AVR
IC407
AVR
MCU Reset
Fig. 8
9. Compander Circuit
The term "compander" means compressor and expand-
er. The compander reduces noise by utilizing a compressor
and an expander. The NX-800/800H contains DSP (IC502) to
perform this operation. The NX-800/800H compander can
be turned on or off using the FPU.
+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