QUANZHOU WOUXUN ELECTRONICS CO., LTD
Model: KG-619
Version: KG-619-0806-V1
Page 8 of 31
Circuit
Circuit
Circuit
Circuit
Description
Description
Description
Description
1
1
1
1
、
、
、
、
Schematic
Schematic
Schematic
Schematic
b
b
b
b
lock
lock
lock
lock
d
d
d
d
iagram
iagram
iagram
iagram
(1)
(1)
(1)
(1)
General
General
General
General
c
c
c
c
ircuit
ircuit
ircuit
ircuit
b
b
b
b
lock
lock
lock
lock
d
d
d
d
iagram
iagram
iagram
iagram
(2)
(2)
(2)
(2)
Transmit
Transmit
Transmit
Transmit
p
p
p
p
rocess
rocess
rocess
rocess
From the chart 1 ( transmit and receive part), we can find that after the local signal
which
comes from VCO being amplified by Q202(2SC3356-R25), Q203(2SC3357)and drived
by Q204(2SK3475), RF power amplifier Q201(2SK3476) will amplify the local signal to 4W,
via receiving and transmitting antenna network to antenna to go to the aerial radiation
The controlled potential of the above drived pin
Q204
and RF power amplifier Q201 is
offered by APC circuit.
The simple description of APC circuit: APC circuit always monitor the current which
through RF power amplifier (Q201) and keep the current stablility. The change of current
that through RF power amplifier will cause R548, R546 and R545’s voltage decrease,
then
to send this voltage to differential amplifier IC4A. IC4 B will compare with the output voltage
of IC4 A and the voltage reference which comes from CPU. The output voltage of IC4 B
control the RF power amplifier, drived pin and keep the same voltage. This voltage commonly