Kenwood TK-2102G Service Manual page 7

XF200:L71-0522-05
Item
Nominal center frequency
Pass band width
40dB stop band width
Ripple
Insertion loss
Guaranteed attenuation
Terminal impedance
5) Squelch
Part of the AF signal from the IC enters the FM IC again,
and the noise component is amplifi ed and rectifi ed by a fi lter
and an amplifi er to produce a DC voltage corresponding to
the noise level.
The DC signal from the FM IC goes to the analog port of
FM IF IC IC200
IF AMP
DET
IC403
MPU
6) Receive Signaling
QT/DQT
300 Hz and higher audio frequencies of the output signal
from IF IC are cut by a low-pass fi lter (IC301). The resulting
signal enters the microprocessor (IC403). IC403 determines
whether the QT or DQT matches the preset value, and con-
trols the MUTE and AFCO and the speaker output sounds
according to the squelch results.
CIRCUIT DESCRIPTION
Rating
38.850MHz
±5.0kHz or more at 3dB
±20.0kHz or less
1.0dB or less
4.0dB or less
80dB or more at fo -910kHz
610Ω /3PF
IC300
AF AMP
DET
HPF
AMP
IC301
LPF
QT/DQT
Fig. 3 AF amplifi er and squelch
CF200:L72-0958-05
Item
Nominal center frequency
6dB band width
50dB band width
Ripple
Insertion loss
Guaranteed attenuation
Terminal impedance
the microprocessor (IC403). IC403 determines whether to
output sounds from the speaker by checking whether the
input voltage is higher or lower than the preset value.
To output sounds from the speaker, IC403 sends a high
signal to the MUTE and AFCO Iines and turns IC302 on
through Q302, Q304, Q305, Q306 and Q307.(See Fig. 3)
Q302
LPF HPF
SW
Q303
W/N SW
3. PLL Frequency Synthesizer
The PLL circuit generates the fi rst local oscillator signal
for reception and the RF signal for transmission.
1) PLL
The frequency step of the PLL circuit is 5 or 6.25kHz.
A 12.8MHz reference oscillator signal is divided at IC1 by
a fi xed counter to produce the 5 or 6.25kHz reference fre-
quency. The voltage controlled oscillator (VCO) output signal
is buffer amplifi ed by Q6, then divided in IC1 by a dual-mod-
ule programmable counter . The divided signal is compared
in phase with the 5 or 6.25kHz reference signal in the phase
comparator in IC1. The output signal from the phase com-
parator is fi ltered through a low-pass fi lter and passed to the
VCO to control the oscillator frequency. (See Fig.4)
TK-2102G
Rating
450kHz
±6.0kHz or more
±12.5kHz or less
2.0dB or less at fo ±4kHz
6.0dB or less
35.0dB or more at fo ±100kHz
2.0 kΩ
IC302
Q307
AF PA AMP
SP
SW
Q304, 305, 306
SW
7