Kenwood TM-V7A Service Manual page 5

TM-V7A/E
CIRCUIT DESCRIPTION
144MHz Band Reception Circuit
After the 144MHz antenna input signals pass through
the final section antenna switching diode, they go through
the front section matching coil, are amplified with the GaAs
field effect transistor, go through a divider, and are amplified
with a single-stage junction field effect transistor. The
unwanted signal is eliminated with a band pass filter made
up of a 3-stage variable-capacity diode chain and the result
goes to the first mixer. In the first mixer, the signals are
mixed with the first local signal from the PLL and converted
to the first intermediate frequency signal of 38.85MHz, then
the unwanted proximate signal is eliminated in the 2-stage
MCF.
The first intermediate frequency signal is amplified and
input to the FM intermediate frequency (IC13). This
intermediate frequency signal is mixed with the second local
oscillator frequency of 38.4MHz to make the second
intermediate frequency of 450kHz and after the unwanted
proximate signal is eliminated with an FM ceramic filter, the
signal is input to IC13 again. Here, second intermediate
frequency amplification and detection are carried out to
form the audio signal.
@S meter circuit
The FM intermediate frequency IC13 S meter output
voltage is connected to the control unit and A/D converted
by the CPU to drive the LCD bar meter.
ltem Rating
_ | Center Frequency 38.85MHz
Pass band width +7.5kHz ot more at 3dB
Attenuation band width | +25kHz ot less at 36dB
+45kHz ot less at 58dB
Guaranteed attenuation | 80dB or more within Fo - (+1000kHz)
(Spurious:40dB or more within +1MHz)
'Ripple 1dB or less
Insertion loss 3dB or less
Termination impedance | 5500 +10%, 2.5pF +0.5pF
Table1 MCF(L71-0482-05) (TX-RX Unit XF1)
430MHz Band Reception Circuit
After the 430MHz antenna input signals pass through
the final section antenna switching diode, they go through
the front section matching coil, are amplified with the GaAs
field effect transistor, go through a divider, go through a
SAW filter to eliminate the unwanted signal and the result is
input to the first mixer. Here, the signals are mixed with the
first local signal from the PLL and converted to the first
intermediate frequency signal of 45.05MHz, then the
unwanted proximate signal is eliminated in the 2-stage MCF.
The first intermediate frequency signal is one-stage
amplified and input to the FM intermediate frequency (1C15).
This intermediate frequency signai is mixed with the second
local oscillator frequency of 45.505MHz to make the second
intermediate frequency of 455kHz and after the unwanted
proximate signal is eliminated with an FM ceramic filter,
second intermediate frequency amplification and detection
are carried out to form the audio signal.
@S meter circuit
The FM intermediate frequency IC15 S meter output
voltage is connected to the control unit microprocessor and
A/D converted by the CPU to drive the S meter.
Item Rating
Center Frequency 45.050MHz
Pass band width +7.5kHz ot more at 3dB
Attenuation band width | +35kHz ot less at 40dB
Guaranteed attenuation | 80dB or more within Fo - (890~930kHz)
(Spurious:40dB or more within +1MHz)
Ripple 1dB or less
Insertion loss 4dB or less
Termination impedance | 8000 +10%, 2pF+0.5pF
Table3 MCF(L71-0481-05)} (TX-RX Unit XF2)
Item Rating
Norminal center 450kHz
frequency .
6dB band width +6.0kHz or more (from 450kHz)
50dB band width +15.0kHz or more (from 450kHz)
Ripple 3dB or less (within 450+5kHz)
Insertion loss 6dB or less (at minimum lost point)
Guaranteed attenuation | 35dB or more (within 450+ 100kHz)
1/0 matching ;
Item Rating
Norminal center 455kHz
frequency
6dB band width +6.0kHz or more (from 455kHz)
50dB band width +12.5kHz or less (from 455kHz)
Ripple 3dB or less (within 455+5kHz)
Insertion loss 6dB or less (at maximum output point)
Guaranteed attenuation | 35dB or more (within 455+100kHz)
terminating impedance
Tabel2 Ceramic filter(L72-0931-05) |
(TX-RX Unit CF1)
VO matching 2.0kQ
terminating impedance
Table4 Ceramic filter(L72-0366-05)
(TX-RX Unit CF2)