TK-5810
(
BG
)
/5810H
(
BG
)
25
Fig. 4 2nd IF
W/N2
W/N2
W/N1
W/N1
SW
IC205
FM/P25
DET
L234
SW
IC201
NARROW/P25
CF200
SW
IC206
SW
DET
DET
COIL
IC202
WIDE
CF201
SW
IC203
SW
IC207
2nd IF
450kHz
1st IF
49.95MHz
2nd Local OSC
50.4MHz
IC209
FM IC
NARROW
CF204
WIDE
CF202
CIRCUIT DESCRIPTION
3-3. 1st IF
The 1st IF signal passes through the MCF (Monolithic
Crystal Filter) to remove unwanted signal.
The MCF has two paths (Wide band: XF201, Narrow
band: XF200), and these are controlled with the IF filter
switch (D208, D209, D210, D211, D212, D213, D214 and
D215).
The signal passes through the MCF (XF201) when the
Wide band (D209, D211, D213 and D215 are ON) is se-
lected. The signal passes through the MCF (XF200) when
the Narrow band (D208, D210, D212 and D214 are ON) is
selected.
The 1st IF signal passing through these MCFs is ampli-
fied by the IF amplifier (Q205) and goes into the FM IC
(IC209).
3-4. 2nd Local
The 1st IF signal (49.95MHz) amplifi ed by the IF ampli-
fi er (Q205) and the 2nd local signal (50.4MHz) generated by
tripling the reference oscillator frequency (16.8MHz) of the
VCXO (X200) by Q207, are mixed in the FM IC (IC209) to
produce a 2nd IF signal (450kHz) (Upper heterodyne).
Fig. 3 1st IF and 2nd local
2nd IF
450kHz
1st IF
49.95MHz
16.8MHz
2nd Local
50.40MHz
SW
Q205
Q204
D214
D215
VCXO
Tripler
Q207
SW
D212
D213
NARROW
XF200
WIDE
XF201
SW
D210
D211
SW
D208
D209
NARROW
XF200
WIDE
XF201
FM IC
IC209
X200
3-5. 2nd IF
The 2nd IF signal passes through the ceramic fi lter to re-
move unwanted signal.
The ceramic fi lter has two paths (Wide band: CF201 and
CF202, Narrow/P25 band: CF200 and CF204), and these
are controlled with the multiplexers (IC201, IC202, IC203,
IC205, IC206 and IC207).
The control line is W/N1, W/N2 and VN.
The signal passes through the ceramic fi lters (CF201 and
CF202) when the Wide band (W/N1: high level, W/N2: high
level, VN: high level) is selected. The signal passes through
the ceramic filters (CF200 and CF204) when the Narrow/
P25 band (W/N1: low level, W/N2: low level, VN: high level)
is selected.
After that, the signal is fed into ASIC (IC708) through ce-
ramic fi lter (CF100), and then, the signal is demodulated in
ASIC and the AF signal is dealing with DSP (IC701).