26
TK-5710
(
B
)
/5710H
(
B
)
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: XF200, Narrow band:
XF201), and these are controlled with the IF filter switch
(D205, D206, D207, D208, D209, D210, D211 and D212).
The signal passes through the MCF (XF200) when the
Wide band (D206, D208, D210 and D212 are ON) is selected.
The signal passes through the MCF (XF201) when the
Narrow band (D205, D207, D209 and D211 are ON) is
selected.
The 1st IF signal passing through these MCFs is amplified
by the IF amplifier (Q203) and goes into the FM IC (IC212).
3-4. 2nd Local
The 1st IF signal (49.95 MHz) amplified by the IF amplifier
(Q203) and the 2nd local signal (50.4 MHz) generated by
tripling the reference oscillator frequency (16.8 MHz) of the
VCXO (X200) by Q205, are mixed in the FM IC (IC212) to
produce a 2nd IF signal (450 kHz) (Upper heterodyne).
3-5. 2nd IF
The 2nd IF signal passes through the ceramic filter to
remove unwanted signal.
The ceramic filter has three paths (Wide band: CF201 and
CF204, Narrow band: CF200 and CF203, APCO band: CF201
and CF202), and these are controlled with the multiplexers
(IC205, IC206, IC207, IC209, IC210 and IC211).
The control line is W/N1, W/N2 and VN.
The signal passes through the ceramic filters (CF201 and
CF204) 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 CF203) when the Narrow band
(W/N1: low level, W/N2: low level, VN: high level) is selected.
The signal passes through the ceramic filters (CF201 and
CF202) when the APCO band (W/N1: high level, W/N2: low
level, VN: low level) is selected.
The APCO signal is A/D-converted by the FPGA IC (IC730)
and DSP IC (IC715), and is performed APCO demodulation.
The detected FM signal and the APCO signal are fed to the
CODEC IC (IC724) respectively.
Fig. 3
1st IF and 2nd Local
Fig. 4
2nd IF
2nd IF
450kHz
1st IF
49.95MHz
16.8MHz
2nd Local
50.40MHz
SW
Q203
Q202
D211
D212
VCXO
Tripler
Q205
SW
D209
D210
NARROW
XF201
WIDE
XF200
SW
D207
D208
SW
D205
D206
NARROW
XF201
WIDE
XF200
FM IC
IC212
X200
W/N 2
W/N 2
W/N 1
W/N 1
VN
VN
SW
IC211
APCO
FM
L232
SW
IC207
NARROW
CF203
SW
IC210
SW
DET
DET
COIL
IC206
APCO
CF202
WIDE
CF204
SW
IC209
SW
IC205
2nd IF
450kHz
1st IF
49.95MHz
2nd Local OSC
50.4MHz
IC212
FM IC
NARROW
CF200
WIDE
CF201