QUANZHOU WOUXUN ELECTRONICS CO., LTD Model: KG-689
Circuit Description
1. Frequency association
Frequency association is shown in Chart 1.
Chart 1
AF AMP
MIX.IF.DET
38.850MHz
1ST MX
RF AMP
ANT SW
PA AMP
TX AMP
(2)
(1)
PLL VCO
MIC AMP
MIC
SP
MCF
450KHz
CF
2nd LO
LPF
ANT
T:400-470MHz
R:400-470MHz
2. Receive system
(1). RF amplifier is shown in Chart 2.
The radio wave enter by antenna, through a low-pass and a transmit/receive switch circuit(D215,D216),
then input to RF amplifier, blow up by T220, the disturb signal will be unchained by band-pass filter.
LPF
ANT SW
BPF
Chart 2
PF AMP
SP
BPF
XF1
MIXER
MCF
IF AMP
MIX.IF.DET
AF AMP
VCO
PLL
ANT
(2). The first mixer
The receive signal and the first PLL unit output root flap signal will mix on the first mixer T233, then give
birth to the first intermediate frequency(IF) signal, except that all disturb signals will be unchained by crystal
filter..
Version: KG-689-0801-V1 Page 5 of 35
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