Circuit Description - Kenwood TM-V708A Service Manual

TM-V708A
Item
Center Frequency
Pass band width
Attenuation band width
Guaranteed attenuation
Ripple
Insertion loss
Termination impedance
Table1 MCF (L71-0491-15) (TX-RX Unit XF100)
Item
Nominal center frequency 450kHz
6dB band width
50dB band width
Ripple
Insertion loss
Guaranteed attenuation
I/O matching
terminating impedance
Table2 Ceramic filter (L72-0979-05)
(TX-RX Unit CF101)
2-5. Audio Circuit
The detected VHF audio signal is amplified by Q108 and
de-emphasized by Q110. The UHF audio signal is amplified
by Q402 and de-emphasized by Q405. One of these audio
signals is selected with a cross point switch (IC702). The
signal passes through the electronic variable resistor (IC804),
is amplified by the AF amplifier (IC806), and fed to the
speaker or the external speaker jack.
SP
PR1
PR9
6

CIRCUIT DESCRIPTION

Rating
38.85MHz
±7.5kHz or more at 3dB
±25kHz or less at 40dB
80dB or more within fo -910kHz
(Spurious:20dB or more within ±1MHZ)
1dB or less
3dB or less
500Ω ±5%, 6pF±0.5pF
Rating
±7.5kHz or more (from 450kHz)
±15.0kHz or less (from 450kHz)
2dB or less (within 450±5kHz)
6dB or less (at minimum lost point)
35dB or more (within 450±100kHz)
1.5kΩ
AF AMP
VR
IC804
IC806
BUFFER
Q701
2SC4617
(R)
BUFFER
Q700
2SC4617
(R)
Fig. 6 Audio Circuit
Item
Center Frequency
Pass band width
Attenuation band width
Guaranteed attenuation
Ripple
Insertion loss
Termination impedance
Table3 MCF (L71-0409-15) (TX-RX Unit XF400)
Item
Nominal center frequency 455kHz
6dB band width
50dB band width
Ripple
Insertion loss
Guaranteed attenuation
I/O matching
terminating impedance
Table4 Ceramic filter (L72-0981-05)
The VHF or UHF audio signal selected by the cross point
switch, passes through the filter circuit (IC701) and goes to
the CPU (IC604) for CTCSS and DCS decoding. The signal
buffered by Q701 is output to the PR1 terminal of the DATA
connector, and the signal buffered by Q700 is output to the
PR9 terminal.
CROSS POINT SW DE-EMPHASIS
Q110
2SC4617
(R)
Q405
2SC4617
(R)
IC702
Rating
45.05MHz
±7.5kHz or more at 3dB
±22kHz or less at 25dB
80dB or more within fo -910kHz
(Spurious:40dB or more within ±1MHz)
1dB or less
4dB or less
800Ω ±10%, 2pF±10%
Rating
±7.5kHz or more (from 455kHz)
±15.0kHz or less (from 455kHz)
2dB or less (within 455±5kHz)
6dB or less (at maximum output point)
35dB or more (within 455±100kHz)
1.5kΩ
(TX-RX Unit CF401)
AF AMP
IF IC
Q108
2SC5108
(Y)
IC100
IF IC
Q402
2SC4617
(R)
IC400