Circuit Description; 电路说明 - Kenwood TK-3230 Service Manual

TK-3230
Frequency Confi guration
Reception method
Transmission method
Modulation
Table 1 Basic confi guration
Receiver System
■ Front End
The high-frequency signal from the antenna passes
through a low-pass fi lter and a high-frequency switch (D101,
D200, D201 and L220) which switches between transmis-
sion and reception, and goes to the BPF (L218) to remove
unwanted signals. The resulting signal is amplifi ed by high-
frequency amplifi er (Q204) and goes to the fi rst mixer (Q203).
■ First Mixer
The signal that reaches Q203 is mixed with the fi rst local
signal from the VCO to produce a fi rst IF signal (38.85MHz).
(Receive frequency – First local frequency
= First IF frequency = 38.85MHz)
The fi rst IF signal passes through MCF: XF200 (monolithic
crystal fi lter) to remove unwanted signals.
The fi rst IF signal is amplifi ed by IF amplifi er (Q201) and
goes to IF IC (IC200).
ANT
LPF
8

CIRCUIT DESCRIPTION /

ANT
460~470MHz
ANT
RF
BPF
SW
AMP
421.15~
431.15MHz
RF RF
AMP AMP
460~470MHz
Fig. 1 Frequency confi guration / 图 1 频率构成
Double super heterodyne
1st IF frequency 38.85MHz
2nd IF frequency 450kHz
VCO direct oscillation amplifi cation
Variable reactance phase modulation
ANT BPF RF AMP
SW L218 Q204
D101
D200
D201
L220
465.0MHz
1st local OSC (PLL)
Fig. 2 Receiver section confi guration / 图 2 接收部分构成
电路说明
频率构成
CF
450kHz
38.85MHz
1st MIX
MCF
MIX, IF
DET
38.4MHz
Tripler
X3
PLL VCO
接收方式
发射方式
调制
接收系统
■前端
天线的高频信号通过低通滤波器和高频开关 ( D101、D200、
D201 和 L220)( 用于切换发射和接收 )，然后进入 BPF (L218)
消除不需要的信号。最终的信号由高频放大器 ( Q204) 进行放
大，然后进入第一混频器 (Q203)。
■第一混频器
到达 Q203 的信号与来自 VCO 的第一本振信号混频，进而产
生第一中频信号 (38.85MHz)。
( 接收信号 – 第一本振信号 = 第一中频 = 38.85MHz)
第一中频信号通过 MCF:XF200( 单片晶体滤波器 ) 消除不需
要的信号。
第一中频信号由中频放大器 ( Q201) 进行放大，然后进入中
频 IC (IC200)。
1st MIXER MCF IF AMP
Q203 XF200 Q201
38.85MHz
SP
AF
AMP
TCXO
12.8MHz
MIC
MIC
AMP
双超外差
第一中频 38.85MHz
第二中频 450kHz
VCO 直接振荡放大
可变电抗相位调制
表 1 基本构成
IF AMP, DET AF AMP
IC200 IC303 SP
2nd local OSC