HYT RPU416A, Manual

Page: 7 / 22

7
RPU416A Circuit Description
The resulting signal goes to the VCO through the VCO modulation terminal for direct FM modulation. (See
Fig. 6)
2) QT/DQT encoder
A necessary signal for QT/DQT encoding is generated by IC403 and FM-modulated to the PLL
reference signal. Since the reference OSC does not modulate the loop characteristic frequency or higher,
modulation is performed at the VCO side by adjusting the balance. (See Fig. 6)
MIC
IC500(1/2)
MIC
AMP
PREEMPHASIS
IC500(1/2)
IDC
Q501.502
LPF
(SPLATTER FILTER)
VR501
MAX
DEV
D5.Q4
VCO
VR500
BALANCE
X1.IC1
REFERENCE
OSC
QT/DQT
IC403
TO
MUTE
Q503
SW
Fig. 6. Transmit audio QT/DQT
3) RF amplifier
The transmit signal obtained from the VCO buffer amplifier Q100, is amplified by Q101 and
Q102. This amplified signal is passed to the power amplifier, Q105 and Q107, which consists of a 2-stage
FET amplifier and is capable of producing up to 4W of RF power (See Fig. 7-b)
D
C
B
A
Title
Number Revision Size
AMP
Q101.102
5T
DRIVE AMP
Q105
FINAL AMP
Q107
ANT SW
D101 LPF
ANT
ANT SW
D102.103
RX
Q106
SW
Q109
SW
5T
IC100
APC
DET
Q103.Q104
B SW
B
APC
5T
TH102
SW
Q110
5T
Q108
SW
Fig. 7 APC system
4) ANT switch and LPF
The RF amplifier output signal is passed through a low-pass filter network and a transmit/receive