SECTION 3CIRCUIT DESCRIPTION
3-1RECEIVER CIRCUITS
3-1-1 VHF ANTENNA SWITCHING CIRCUIT
(PA UNIT)
Incoming VHF signals from the antenna connector are
passed through aChebyshev 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 alow-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 afirst 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 aChebyshev low-pass filter consisting
of LI 3, LI 4, C35, C36 and C37 and aChebyshev 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 atuned 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 afirst 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 2tuned 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 alimiter for strong signals. The amplified
signal from Q4 is fed to pin 16 of IC1. IC1 incorporates a
second oscillator, asecond mixer, alimiter and a
discriminator on asingle chip. The signal from pin 16 of IC1
is mixed with the second oscillator signal to produce the
455kHz signal at pin 3on IC1 .The 455kHz signal is filtered by
ceramic filter FI2 and is fed to pin 5of 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 9on IC1.
3-1-6 AUDIO AMPLIFIER CIRCUIT (MAIN UNIT)
The audio signal from pin 9on IC1 is amplified by Q10, is
filtered by active filter Q11, and is fed through J7 and the
VOLUME CONTROL to pin 1on 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 9on IC1 is also fed to the noise
amplifier through C69, R50, J8, C70, and the SQUELCH
CONTROL and then is input to pin 10on IC1 .The amplified
noise signal exits from pin 11on IC1 ,is rectified by D1 1and
D12, and is controlled by 09 through R54.
3-1-8 S-METER CIRCUIT (MAIN UNIT)
S-meter signals from pin 5on 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 AUNIT 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.
3-2TRANSMITTER CIRCUITS
3-2-1 MIC AMPLIFIER CIRCUIT (PLL UNIT)
The microphone output is fed into IC5A through C60andthe
08 amplifier. IC5A includes adifferential 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 alow-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
adifferent microphone with the IC-3200A, be sure it has the
proper output level before making any connections.
Particular care should be exercised when wiring adifferent
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.
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