14
TK-6110
CIRCUIT DESCRIPTION
Noise
amp
Noise
amp
DET
Q206
D206
Output
expander
IC604
CPU
Mute
circuit
31
SQL
7
DET
OUT
8
9
AF OUT
IC202
Fig. 4
squelch circuit
12
HPF
LPF
HPF
IDC
PRE
EMP
ALC
COMP
SW
LIMIT
D711
IC713
15
16
18
19
Q708
MM
TONE
9
8
6
D/A
IC710
IC712
I4
O4
LSD
IC711 (1/2)
SUM
AMP
IC714 (2/2)
AMP
MIC1
SW
SW
SW
VCO
L517
MIC2
MC1
MC2
(External
input)
Fig. 5
Microphone circuit
3-4. Audio Amplifier Circuit
The recovered audio signal obtained from IC202 is ampli-
fied by IC709, IC713, low-pass filtered by IC713 high-pass
filtered by IC713 and band-eliminate filtered by IC713.
The audio signals then passed through a de-emphasized
by IC713. The processed audio signal passes through an
audio volume control and is amplified to a sufficient level to
drive a loudspeaker by an audio power amplifier BTL
(IC102).
4. Transmitter System
4-1. Microphone Amplifier
The signal from the microphone is high-pass filtered by
IC713, passed through microphone mute and microphone
amplifier circuit (Q703 and IC714), limited and pre-empha-
sized by IC713 and D711.
4-2. Modulator Circuit
The output of Audio-processor (IC703) is passed to the D/
A converter (IC710) for maximum deviation adjustment and
the summing amplifier (IC711) before being applied to a
varactor diode in the voltage controlled oscillator (VCO) lo-
cated in the frequency synthesizer section.
4-3. Down-Mixer
At Q503, a modulated VCO2 signal is mixed with 2nd lo-
cal oscillator signal, 129.005MHz. The difference of the two
signals is used for the transmission signal 29.7~37MHz (K),
35.0~50.0MHz (K2). The output was filtered through a low-
pass filter.
Fig. 3
Audio amplifier circuit
HPF
IC713
IC202
FM IF SYSTEM
CF201,202
455kHz
HPF
LPF
BEF
IC203
DE-
EMP
EXP
VOL
SW
MUTE
129.005
MHz
2
1
5
41
IC709 (2/2)
AF AMP
IC711 (2/2)
AF AMP
IC710
VOL
IC710
AF
AMP
IC102
MUTE
IC105
ES2
AM1
3-5. Squelch Circuit
The output signal from IC202 enters FM IC again, then
passed through a band-pass filter. The noise component
output from IC202 is amplified by Q206 and rectified by
D205 to produce a DC 0 voltage corresponding to the noise
level. The DC voltage is sent to the analog port of the CPU
(IC604).
And IC202 outputs a DC voltage (RSSI) corresponding to
the input of the IF amplifier.