QUANZHOU WOUXUN KG-619, Service Manual, Page: 10 / 32

QUANZHOU WOUXUN ELECTRONICS CO., LTD Model: KG-619
Version: KG-619-0806-V1 Page 9 of 31
Circuit Circuit Circuit
Circuit
Description Description Description
Description
known as transmitting EPC(Electronic power control).
The change of high/low power is achieved through reference voltage.
(3) (3) (3)
(3)
Receive Receive Receive
Receive
p p p
p
rocess rocess rocess
rocess
The signal received from antenna, after through the receive/transmit switch and
BFP(L413,L414) will be amplified by RF amplifier Q409(3SK318). This signal will go into the
mixer Q408 through BFP(L409,L410) and mixing with the local first oscillator signal which
comes from VCO, then generated the useful signal of the first intermediate frequency signal
38.5MHz. After filtering by crystal filter (FL403, L402), then amplifying by Q427 and going
into RF IC(IC401 LM31136)
，
it will mixing in RF IC with 2 octave of the second local oscillator
signal which comes from temperature compensated crystal, then get the second
intermediate frequency 450K, filtering through ceramic filter FL401 and being frequency
discrimination by CR401, after it , signal will output from the 9th pin of RF IC(IC401
LM31136).
The above two band-pass filters BFP can be adjusted D408, D409, D406, D407(1SV305)
through variable capacitor. The variable voltage of the variable capacitor is provided by the
23
rd
pin of the CPU and commonly known as receiving EPC(Electronic power control).
The signal that output from the 9
th
pin of RF IC(IC401 LM31136) goes into the 16
th
pin of CPU, after this signal filtering by CPU, then will processing signaling (CTCSS/DCS). If
the receiving has set the signaling, the parameter of signaling that after processing by CPU
must keep the same with the preset parameter. The voice frequency signal that output from
the 25
th
pin of CPU will be amplified by Q420, then the process of signal becomes two
pathes:
①
With With With
With
s s s
s
crambler crambler crambler
crambler
s s s
s
et et et
et
(Optional (Optional (Optional
(Optional
accessory) accessory) accessory)
accessory)
It goes into the scrambler IC701 (14th pin), after scrambler IC701 encrypted the voice
frequency signal, this signal will output from the 17
th
pin of the scrambler IC701 and
through the 8
th
pin of the line seat, it return to the CPU from the 7
th
pin of the line seat
through volume potentiometer, and drive the SPK after amplified by audio frequency power
amplifier integration IC3.