TH-K2AT/K2E/K2ET
13
■
CTCSS/ DCS
The encode signal is generated by the M PU (IC8) and output
from the TONE terminal (pin 41) of the M PU.
The unw anted high-frequency components of the encode
signal output from the M PU are removed w ith a low -pass filter,
and applied to VCO modulation input (M OD) and TCXO VC
terminal for modulation.
The VCO and TCXO modulation levels are adjusted by VR6
to produce flat modulation characteristics in low and high
ranges.
The decode signal is input to the SIGIN pin (pin 47) of the
M PU after the w aveform of the audio signal from the FM IC is
rectified w ith a CTCSS/DCS filter (IC17). Then the set CTCSS
tone frequency and DCS code are detected by digital signal
processing in the M PU to control muting.
LPF
VR6
VCO
VOL OUT
M OD
X1
TCXO
VC
IC16
1
6
M IC
AM P
IC5
HPF
M IC
IC6
AF AM P
Vin
IC8
M PU
TONE
41
40
47
111
9
SIG IN
VOX IN
NOAA
K, K2 types only
DTM F/BEEP
IC17
D24
Q30
IC3
CTCSS/DCS
FILTER
FM
IC
50
VR
5
AM P
■
DTM F
The DTM F signal is generated by the M PU (IC8) and is
output from the DTM F/BEEP terminal (pin 40) of the M PU.
The DTM F signal is mixed w ith an audio signal at the input
side of the AF amplifier (IC6), and is output as a monitor tone.
The DTM F signal is mixed w ith a modulation signal at the
input side of pre-emphasis in the microphone amplifier (IC16)
and used as a transmit signal.
■
VOX
The IC5 and Q30 amplify the audio signal captured in the
microphone, and then the signal is converted into the DC
Voltage D24 rectifies.
The DC voltage activates the M PU (IC8), and the VOX starts.
■
Weather Alert (K and K2 types only)
The IC17 apmlifies the detected signal from the FM IC (IC3),
and the M PU (IC8) processes the signal. This signal processing
activates Weather Alert function.
Fig. 15 CTCSS/ DCS, DTM F, VOX, Weather alert
■
Serial Control
Serial control must be enabled from a transceiver menu so
that the REM /TXD pin of the speaker jack (J4) and the PTT
(RXD) pin of the microphone jack (J3) function as TXD and
RXD, respectively, w hen communicating w ith a personal
computer.
SP
POUT
10
HPF
IC5
IC6
AF AM P
PTTE
TXD
RXD
REM
IC8
M PU
SPK
AFO
SPG
REM /TXD
13
46
J4
SP JACK
IM
5M S
+
–
PTT
M IC
J3
M IC JACK
5M C
12
11
M IC
Fig. 16 Serial control
CIRCUIT DESCRIPTION