Kenwood TK-2107 Service Manual page 6

TK-2107
XF200:L71-0535-05
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 amplified and rectified by a filter
and an amplifier to produce a DC voltage corresponding to the
noise level.
The DC signal from the FM IC goes to the analog port of the
microprocessor (IC403). IC403 determines whether to output
6) Receive signaling
QT/DQT
300 Hz and higher audio frequencies of the output signal
from IF IC are cut by a low-pass filter (IC301). The resulting
signal enters the microprocessor (IC403). IC403 determines
whether the QT or DQT matches the preset value, and
controls the MUTE and AFCO and the speaker output sounds
according to the squelch results.
TK-260 :K, K2
6
CIRCUIT DESCRIPTION
Rating
38.850MHz
7.5kHz or more at 3dB
40.0kHz or less
1.0dB or less
3.0dB or less
80dB or more at fo -1000kHz
1200 / 1.4PF
FM IF IC IC200
IF AMP DET
HPF
DET
AMP
IC301
LPF
QT/DQT
IC403
MPU
Fig. 3 AF Amplifier and squelch
CF200:L72-0979-05
Item
Nominal center frequency
6dB band width
50dB band width
Ripple
Insertion loss
Guaranteed attenuation
Terminal impedance
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)
IC300
AF AMP Q302
LPF HPF
SW
Q303
W/N SW
3. PLL frequency synthesizer
The PLL circuit generates the first 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 fixed
counter to produce the 5 or 6.25kHz reference frequency. The
voltage controlled oscillator (VCO) output signal is buffer
amplified by Q6, then divided in IC1 by a dual-module
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 comparator is filtrered
through a low-pass filter and passed to the VCO to control the
oscillator frequency. (See Fig.4)
Rating
450kHz
7.5kHz or more
15kHz or less
2.0dB or less at fo 5kHz
6.0dB or less
35.0dB or more at fo 100kHz
1.5 k
IC302
Q307
AF PA AMP
SP
SW
Q304, 305, 306
SW