Circuit Description - Kenwood TK-3160 Service Manual

TK-3160
1. Frequency Configuration
The receiver utilizes double conversion. The first IF is 49.95
MHz and the second IF is 450 kHz. The first local oscillator
signal is supplied from the PLL circuit.
The PLL circuit in the transmitter generates the necessary
frequencies. Fig. 1 shows the frequencies.
2. Receiver
The frequency configuration of the receiver is shown in Fig. 2.
1) Front End (RF AMP)
The signal coming from the antenna passes through the
transmit/receive switching diode circuit, (D204,D206,D208
and D212) passes through a BPF (L413 and L414), and is
amplified by the RF amplifier (Q404).
The resulting signal passes through a BPF (L409,L408 and
L407),and goes to the mixer. These BPFs are adjusted by
variable capacitors (D402,D403,D404,D405 and D406). The
input voltage to the variable capacitor is regulated by
voltage output from the microprocessor (IC805).
2) First Mixer
The signal from the front end is mixed with the first local
oscillator signal generated in the PLL circuit by Q403 to
produce a first IF frequency of 49.95 MHz.
The resulting signal passes through the XF401 MCF to cut
the adjacent spurious and provide the opitimun
characteristics, such as adjacent frequency selectivity.
10

CIRCUIT DESCRIPTION /

ANT TX/RX: 440 ~ 480MHz (C)
400 ~ 430MHz (C2)
RF
ANT SW
AMP
RX: 390.05~430.05MHz (C)
TX: 440 ~ 480MHz (C)
400 ~ 430MHz (C2)
TX
AMP
Fig. 1 Frequency configuration / 图 1 频率构成
ANT
RF AMP
Q404
BPF
ANT SW
TUNE
CF401
IC602
AF Amp
IC401
IF,MIX,DET
X1
Q4
TCXO 16.8MHz
X3 multiply
2nd Local
Fig. 2 Receiver section / 图 2 接收部
电路说明
1 . 频率构成
本接收机使用二次变频。第一 IF 是 49.95 MHz，第二 IF 是
450 kHz。第一本地振荡信号由 PLL 电路提供。
PLL 电路产生需要的发射频率。
CF
450kHz
MCF
AF
IF SYSTEM
AMP
49.95MHz
50.4MHz
X3 multiply
TCXO
16.8MHz
350.05~380.05MHz (C2)
RF PLL
MIC
AMP
VCO
AMP
2 . 接收部
接收部的频率构成如图 2 所示。
MIXER MCF
Q403 XF401
BPF
1st Local
TUNE
IC601
IC605
AF VOL AF PA
AQUA
1) 前端 (RF 放大器)
从天线接收的信号进入发送 / 接收转换开关二极管电路
(D204，D206，D208 和 D212)，然后通过 BPF (L413 和 L414)，
并且被 RF 放大器 (Q404) 放大。
此信号通过 BPF (L409，L408 和 L407) 然后进入混频。这些
BPF 被可变电容器 (D402，D403， D404，D405 和 D406) 调整。
输入可变电容器的电压被经微处理器 (IC805) 的电压输出调
整。
2) 第一混频器
前端的信号与 PLL 电路产生的第一本振信号在 Q403 混频 , 生
成 49.95MHz 频率的第一中频信号。
生成的信号通过 XF401 MCF。
SP
MIC
IF AMP
Q402
SP