
7. AF and Mute Circuit
(Main unit)
8. Squelch Circuit
(CPU unit)
The AF signal from IC1 is filtered by the low-pass filter amplifier (Q2) and led to the
high-pass filter amplifier (Q1), and output to the AF gain volume. Q3 and Q4 are
switched ON/OFF by AFC signal from CPU, then AF signal is muted when the
squelch is ON.
IC1 has the noise amplifier, rectifier circuit and comparator circuit. The noise signal
from pin 12 of IC1 is input to the noise amplifier (pin19 of IC1) and passed through
buffer amplifier (Q28), rectified by D8, then it is input to comparator circuit (pin 21
of IC1). When the noise signal is decreased by the receiving signal, the compara
tor output SD becomes low.
2) Transmitter System
1. Microphone Amplifier Circuit
(CPU unit)
2. Limiter Amplifier Circuit
(Main unit)
3. Modulation Circuit
(VCO unit)
4. Drive Amplifier Circuit
(Main unit)
The voice from external microphone is amplified by the microphone amplifier
(Q303), and passed through the microphone mute circuit (Q304), the signal is
input to the microphone gain potentiometer (VR3) in the main unit.
The signal from microphone gain potentiometer (VR3) is amplified by limiter
amplifier and low-pass (IC4). The resulting signal is passed through the modula
tion adjustment potentiometer (VR4), then input to VCO unit. IC4A is limiter
amplifier with pre-emphasis characteristics. IC4B is low-pass filter.
The adjusted AF signal in VR4 is led to the VCO unit. The frequency modulation is
executed when the audio signal is supplied to the D207.
The signal from VCO unit is input to the drive amplifier (IC3). IC3 has high gain of
approximately 30dB and high level of approximately 10dBm wide band amplifier.
5. RF Younger Amplifier Circuit
(Main unit)
The signal from IC3 is passed through diode switch D12, and input to younger
amplifier Q13. Q13 has approximately 15dB gain and output level is 400mW. The
output signal of younger amplifier is led to the PA amplifier (IC2).
Содержание DR-140E
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Страница 19: ...EXPLODED VIEW 19 ...
Страница 31: ...5 Adjustment Points 28 ...
Страница 32: ...m ïJ ù m m m BPS m W aSS 29 ...
Страница 36: ...C N 5 0 1 7 EJ 20U CTCSS Unit Option CD R 5 1 4 R 5 1 5 R 5 0 4 33 ...
Страница 38: ...1 M a in U n itT E ...
Страница 41: ...4 O XC225 0 001 8 1 4EU Ver C213 C247 TE 100P 5P TE1 150P 6P TE2 120P 4P BV 200P 5P 4 V C O Unit ...
Страница 42: ... F 5 EJ 20U CTCSS Unit Option ...