RP3000 Circuit Description
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3) IF Amplifier
The first IF signal is amplified by Q216 before passing through crystal filter and by Q222 after crystal
filter and then enters IF processing chip IC204. The signal is mixed with the second local oscillator
signal again in IC204 to create a 455KHz second IF signal. The second IF signal then passes
through a 455KHz ceramic filter (wideband: CF201/narrowband: CF202) to eliminate unwanted
signals before it is amplified and detected in IC204.
4) Narrowband/Wideband Switch Circuit
Turn on ceramic filter CF201 (wideband)/CF202 (narrowband) to set each channel as wideband or
narrowband. W/N pin of IC500 outputs wideband (high level) and narrowband (low level) signal.
5) AF Amplifier
The result AF signal from IC204 is amplified by IC606, and then passes through AF processing chip
IC601 and compander IC603. The processed AF signal is then amplified by an AF power amplifier
(IC720) to drive the speaker.
4. Transmitter
1) AF and Signaling
Modulating signal from the microphone passes through Q700 switch and compander IC603 before
it enters AF processing chip IC601. CPU generates CTCSS/CDCSS signaling and IC601 produces
DTMF/2-Tone/5-Tone signaling, which then pass through MOD and enter VCO together with the
modulating signal for direct FM modulation. (See fig.5)
2) RF Amplifier
The transmit signal from VCO buffer amplifier (Q310) is amplified by Q101 and Q102. The
amplified signal is then amplified by the power amplifier Q105 and Q107 (include a two-stage FET
amplifier) to create 4.0W RF power. (See fig.4)
D
C
B
A
Title
AMP
Q101.102
5T
DRIVE AMP
Q105
FINAL AMP
Q107
ANT SW
D101
LPF
ANT
ANT SW
D201.202
RX
Q106
SW
Q109
SW
5T
IC100
APC
DET
Q103.Q104
B SW
B
APC
5T
TH101
SW
Q110
5T
Q108
SW
5TC
Fig.4 APC System