Circuit Description - Kenwood TK-3207 Service Manual

TK-3207
1. Frequency Configuration
The receiver utilizes double conversion. The first IF is 38.85
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, (D103,D104,D106
and D122) passes through a BPF (L229 and L228), and is
amplified by the RF amplifier (Q205).
The resulting signal passes through a BPF (L214,L212 and
L211) and goes to the mixer. These BPFs are adjusted by
variable capacitors (D203,D204,D205,D206 and D210). The
input voltage to the variable capacitor is regulated by
voltage output from the microprocessor (IC405).
2) First Mixer
The signal from the front end is mixed with the first local
oscillator signal generated in the PLL circuit by Q1 to
produce a first IF frequency of 38.85 MHz.
The resulting signal passes through the XF201 MCF to cut
the adjacent spurious and provide the opitimun
characteristics, such as adjacent frequency selectivity.
12

CIRCUIT DESCRIPTION /

ANT TX/RX: 450 ~ 490MHz (M)
440 ~ 480MHz (C)
400 ~ 430MHz (C2)
RF
ANT SW
AMP
RX: 411.15 ~ 451.15MHz (M)
TX: 450 ~ 490MHz (M)
440 ~ 480MHz (C)
400 ~ 430MHz (C2)
TX
AMP
Fig. 1 Frequency configuration / 图 1 频率构成
ANT
RF AMP
Q205
BPF
ANT SW
TUNE
CF201
IC201
IF,MIX,DET
X1
Q1
TCXO 12.8MHz
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 38.85 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
38.85MHz
38.4MHz
X3 multiply
TCXO 12.8MHz
401.15 ~ 441.15MHz (C)
361.15 ~ 391.15MHz (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
Q204 XF201
BPF
1st Local
TUNE
IC301
IC302
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
(D103，D104，D106 和 D122)，然后通过 BPF (L229 和 L228)，
并且被 RF 放大器 (Q205) 放大。
此信号通过 BPF (L214，L212 和 L211) 然后进入混频。这些
BPF 被可变电容器 (D203，D204，D205，D206 和 D210) 调整。
输入可变电容器的电压被经微处理器 (IC405) 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 Q1 混频 , 生成
38.85MHz 频率的第一中频信号。
生成的信号通过 XF201 MCF。
SP
MIC
IF AMP
Q203
SP