Kenwood NX-820H Service Manual page 16

NX-820H(G)/820H
8. Signaling Circuit
8-1. Encode (QT/DQT/DTMF/2TONE/MSK)
Each signaling data signal of the QT, DQT, DTMF, 2TONE
and MSK is generated by the DSP circuit, superposed on a
modulation signal and output from the ASIC (IC507). Each
deviation of the TX QT, DQT, DTMF, 2TONE and MSK tones
are adjusted by changing the output level of the DSP (IC502)
and the resulting signal is routed to the VCO and PLL.
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
by the DSP.
9. Compander Circuit
The term "compander" means compressor and expander.
The compander reduces noise by utilizing a compressor and
an expander. The DSP (IC502) performs this operation. The
ompander can be turned on or off using the FPU.
10. GPS Circuit (GPS model only)
The GPS information function can be used by setting it
through the FPU. The GPS signal of 1575.42MHz received
with the GPS active antenna (with a built-in LNA) is pro-
cessed by the GPS module (A801) and input to the ASIC
(IC507) through the UART port. The ASIC (IC507) processes
the GPS data (NMEA) and sends the resulting information to
the LCD.
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CIRCUIT DESCRIPTION