(4)
WFM
mode
The
2nd
IF signals from the IF amplifier (05) pass through
F12,
are amplified at
052
and are then applied to the
FM
IF
IC
(IC9 pins
2,
3)
where the IF signals are converted into
AF signals. The detected AF signals from pin 8 are then
applied to the AF selector switch (IC15 pin 11).
The amplified or compressed signals are applied to the VCA
section of IC22. The microphone gain setting from the
O/A
converter (IC35 pin 11) is applied to the VCA control ter-
minal (IC22 pin 10). The resulting signals from pin 9 are
then applied to the buffer amplifier (063). External modu-
lation input from the [ACC] socket (pin 11) is also applied
to·
063.
3-1-14 AF SELECTOR SWITCH (MAIN UNIT)
The AF amplifier amplifies the AF input signal to a suitable
driving level for the speaker.
[VOX
GAIN]
(R239)
14
AFO
-signal
MIGC from
O/A
converter (IC35)
:
10
15
[ANTI
VOX]
(R244)
VXS8
VOX
OFF:
8 V
VOX
ON:
oV
While
in
FM/AM mode, the amplified signals from
063
are
applied to the limiter amplifier (IC24a) and splatter filter
(IC24b). The signals are then applied to the AF selector
switc'l (IC23)
in
AM
mode or to the varactor diode (067)
in
FM
mode.
While in SSB mode, the amplified signals from
063
are
applied to the AF selector switch (IC23) and then to the
balanced modulator (IC17).
MIC 22
signal
VOXO ...
17
t+--<
to CPU
Microphone amplifier
[COMP GAIN] COMS
(R248) from CPU
__No/'_
•
IC22 : 2. 3 i
11
AFI
to PLL
unit
CW
side
tonel
beep tone
Optional
synthesized voice
Squelch
control
The AF signal from one of the detector circuits is applied to
the AF selector switch (IC15). IC15 consists of dual
4-channel analog switches which are selected with a mode
signal
and
the squelch control signal.
3-1-15
AF
AMPLIFIER CIRCUIT
(MAIN AND
PLL
UNITS)
AF selector switch
IC15
SSB/CWI
12
xo
RTTY
AM
14
Xl
X
13
FM
15
X2
•
WFM
11
X3
..........
8
INH
9.
10
AFS1, AFS2
The
AF
signal from the AF selector switch (IC15)
is
applied
to the
AF
amplifier (053). The
CW
side tonelbeep tone
and
optional synthesized voice are also applied to 053. The
amplified signal is then applied to the PLL unit.
The signals from the
MAIN
unit are applied to the VCA
(Voltage Controlled Amplifier, IC4) circuit. The AF gain
setting from the main
CPU
is
converted to
DC
voltage at the
O/A
converter (MAIN unit IC35) and applied to the VCA
control terminal (IC4 pin
8)
via the "AFGC" signal line. The
AF signal from IC4 (pin
9)
is power-amplified at IC5 to drive
the speaker.
3·2 TRANSMITTER CIRCUITS
3-2-1 MICROPHONE AMPLIFIER CIRCUIT
(MAIN UNIT)
The microphone amplifier circuit amplifies microphone input
signals and outputs the amplified signals to the balanced
modulator or
FM
modulation circuit.
3-2-2 VOX CIRCUIT (MAIN UNIT)
The vox (Voice-Operated-Transmission) circuit sets trans-
mitting conditions according to voice input. The microphone
amplifier
IC
(IC22) includes the VOX circuit.
The microphone signals from IC22 (pin 19) pass through
the [VOX GAIN] control (R239) and are then applied to the
VOX comparator section (IC22 pin 18) to switch the keying
input of the main
CPU
(IC25 pin 14). When voice levels
exceed the reference level, the VOX circuit sets the trans-
ceiver to transmit.
On
the other hand, a speaker drive signal from the AF
power amplifier (PLL unit IC5) is applied to the anti-VOX
comparator section (IC22 pin 14) via the [ANTI VOX] control
(R244). When the audio output level increases, this compa-
rator cuts out the
VOX
comparator via the MUTE terminal
(IC22 pin 16).
Audio signals from the front or rear panel [MIC] connector
enter the microphone amplifier
IC
(IC22
pin
22)
and
are
then amplified at the microphone amplifier or speech com-
pressor section. Compression level is adjusted with the
[CaMP GAIN] control (R248).
3-2-3 BALANCED MODULATOR (MAIN UNIT)
The balanced modulator converts the AF signal from the
microphone amplifier to a 9 MHz IF signal with a
BFa
(Beat
Frequency Oscillator) signal.
3-4
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