SECTION 3 CIRCUIT
DESCRIPTION
3
-
1 RECEIVER CIRCUITS
3-1-1
VHF
ANTENNA SWITCHING CIRCUIT
(PA UNIT)
Incoming VHF signals from the
antenna connector are
passed
through
a
Chebyshev Low-pass filter consisting of
L3, L4, L6, Cl
2,
Cl
3,
Cl
4,
and
Cl
5,
and are
fed to
the
antenna switching circuit. While receiving, D2 is turned ON.
Receive
signals
from a low-pass
filter are
passed
through
another filter consisting of Cl
0,
L2
and
Cl
7,
and are fed to
J1
on the MAIN UNIT.
3-1-2
VHF RF AMPLIFIER
CIRCUIT (MAIN UNIT)
Signals from J1 are passed
through the L1-L2 bandpass
filter, and are amplified
by
Q1. Amplified signals from Q1 are
passed
through the L3-L4-L5 bandpass filter, and are mixed
with the local oscillator signal from the PLL circuit in Q2 to
produce a first IF signal of 30.875MHz.
3-1-3
UHF
ANTENNA SWITCHING CIRCUIT
(PA UNIT)
Incoming
VHF signals from the antenna connector are
passed through both a
Chebyshev low-pass filter consisting
of LI
3,
LI
4,
C35, C36
and
C37
and a
Chebyshev low-pass
filter consisting of L11, L13,
C32, C33
and C34
before being
fed
into the
antenna switching circuit. While receiving,
D5
is
turned OFF. Receive signals from the low-pass
filter are
passed
through another filter consisting
of
L10, C30, C39
and
C40,
and are fed to J3
on the MAIN UNIT.
3-1-4
UHF RF AMPLIFIER CIRCUIT (MAIN UNIT)
Signals from
J3
are passed
through
a tuned
circuit
consisting of L1
1 ,
C21
and
C22,
and the output is amplified
by
Q5. The output from Q5 is passed
through bandpass filter
L13, amplifier
Q6,
bandpass filter
LI
5,
and is mixed with the
local oscillator signal
from
the
PLL UNIT
to
produce
a
first IF
signal
of 30.875MHz.
3-1-5
IF AMPLIFIER CIRCUIT
(MAIN
UNIT)
The
first
IF signal from
the
mixer is
passed
through the
L8-C1 2
tuned circuit, is filtered
by
crystal filter Fit
,
is
passed
through the L9-C15 tuned circuit, and is amplified
by
Q4. D3
and D4 function as a limiter for strong signals. The amplified
signal from Q4 is fed to pin 16 of IC1. IC1 incorporates a
second oscillator, a second mixer, a limiter and a
discriminator on a single chip. The signal from pin 16 of IC1
is mixed
with
the
second oscillator signal
to
produce the
455kHz
signal
at
pin
3
on
IC1 .
The
455kHz
signal is filtered
by
ceramic
filter
FI2
and is fed
to
pin
5
of IC1 where it then
enters the limiter amplifier. The
amplified signal
is fed to
the
discriminator through ceramic discriminator unit
XI. The
audio signal exits from pin 9 on IC1.
3-1-6
AUDIO
AMPLIFIER CIRCUIT (MAIN UNIT)
The audio
signal from pin
9
on IC1 is
amplified
by Q10,
is
filtered by active filter
Q11,
and
is fed
through
J7 and the
VOLUME CONTROL to pin
1 on
105. IC5 is the audio power
amplifier. The amplified audio signal from IC5 is fed to the
speaker through
J10.
3-1-7
SQUELCH CIRCUIT (MAIN UNIT)
The audio signal from
pin
9
on IC1 is also fed to the noise
amplifier through
C69,
R50, J8,
C70,
and the
SQUELCH
CONTROL and then is input to pin 1 0 on IC1 . The amplified
noise signal exits from pin
1
1
on
IC1
,
is
rectified
by
D1
1
and
D12, and is controlled by 09
through R54.
3-1-8
S-METER CIRCUIT (MAIN UNIT)
S-meter signals from pin
5
on IC1 are amplified
by
IC3
through
C66
and R49, are passed through L20, are rectified
by D9
and DIO, and are fed to the LCD driver circuit on the
LOGIC
A
UNIT through J12.
In
the
VHF mode, the band
signal turns ON Q12 to adjust the gain of IC3 by means of
R82, equalizing the S-meter
level
between
VHF and
UHF.
3
-
2 TRANSMITTER CIRCUITS
3-2-1
MIC AMPLIFIER CIRCUIT (PLL UNIT)
The microphone output is
fed into IC5A through C60andthe
08 amplifier.
IC5A includes a differential amplifier
and
a
limiter
amplifier with
R2
as the UHF
deviation gain
adjustment and R3 as the
VHF deviation gain adjustment.
Preemphasis of 6dB/octave is introduced
between
300Hz
and 3kHz.
The signal
is
then fed
to
the FM modulator in the
TX VCO UNIT through a low-pass filter consisting
of
IC5B,
R45, R46, R49,
C51, C52,
and
C53.
3-2-2
MICROPHONES USED WITH THE IC-3200A/E
The IC-3200A/Ecomesfactoryequipped with a
high-quality
electret condenser microphone. The type of supplied
microphone varies with each transceiver model. The
microphone
types
are listed below.
IC-3200A
(#03)
; IC-HM14 (DTMF Encoder)
IC-3200E
(#04)
; IC-HM15 (1750Hz Tone Burst)
IC-3200A
(#05)
: IC-HM12
1. IC-HM14 (DTMF Encoder) MIC
Plug the IC-HM14 into the
MIC
CONNECTOR on the front
panel for
immediate transceiver
operation.
If
you
wish
to use
a different microphone
with the IC-3200A,
be
sure it
has the
proper output level before making any connections.
Particular care should be
exercised
when wiring a different
microphone since the
internal electrical switching
system in
the transceiver depends
on proper connections being made.
See the diagram on page
3-2
for proper MIC wiring
instructions.
3—
1
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