4 - 2
• RX AF CIRCUITS
AF
AM P
IC55 TPA0211DGN
J52
IC62
RX
MUTE
SP1
HPF
IC58
AF
AM P
IC12
TA7368F
HPF
IC58
J53
Int.speaker
Ext.speaker
1
2
LPF
IC58
LPF
IC59
the demodulator
circuits
IC56
AF line SW
CD4066
AFON
AFO
RMUT 1
D/A
converter
IC57
R2A20178
RX AF CIRCUITS
The demodulated AF signal from the IF demodulator
IC is passed through the LPF, HPF which attenuates
frequencies 300 Hz and below. The filtered AF signal is
passed through the AF line SW, HPF which additionally
attenuates frequencies 300 Hz and below, de-emphasis
circuit which provides –6 dB/oct of frequency response.
The de-emphasized AF signal is passed through the AF
SW, LPF which attenuates frequencies 3 kHz and above, is
adjusted in level by the D/A converter. The level-adjusted AF
signal is then applied to the AF power AMP via the AF line
SW.
The amplified AF signal is applied to the internal or external
speaker.
4-2 TRANSMITTER CIRCUITS
TX AF CIRCUITS
The audio signal from the internal or external microphone
(MIC signal) is passed through the MIC gain SW and applied
to the MIC AMP. The amplified MIC signal is passed through
the MIC mute SW, HPF which attenuates frequencies
300 Hz and below. The filtered MIC signal is passed through
the pre-emphasis circuit which pr6 dB/oct of
frequency response, then they applied to the limiter AMP.
The amplitude-limited MIC signal is passed through the
MIC line SW, and applied to the splatter filter, which
attenuate harmonics in the MIC signal to prevent exceeding
permissible deviation.
The filtered MIC signal is applied to the D/A converter which
adjusts its level (=deviation). The level-adjusted MIC signal
is applied to the TX VCO as the modulation signal.
• TX AF CIRCUITS
AM
limit
P
IC58
MIC
MUTE
IC62
MIC
GAIN
SW
IC62
HPF
IC58
MC51
AM
MIC
P
IC60
LPF
IC58
Splatter
J51
Ext.MIC
Int.MIC
D/A
MOD
To the modulation circuits
IC56
MIC
line
SW
CD4066
IC57
MODULATION CIRCUIT
The modulation signal from the TX AF circuits is applied to
D15 of the TX VCO to frequency-modulate it. The frequency-
modulated signal from the TX VCO is buffer-amplified by
two buffers, and applied to the TX AMP circuits via the TX/
RX SW (D5).
• MODULATION CIRCUITS
LO
SW
D5,D6
Q14,D16
FREQUENCY
MODULATION
D15
BUFF
Q8
BUFF
Q10
TX VCO
From the TX AF circuits
To the TX AMP circuits
