Circuit Description - Kenwood TK-2207 Service Manual

TK-2207
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,D105
and D106) passes through a BPF (L214 and L213), and is
amplified by the RF amplifier (Q205).
The resulting signal passes through a BPF (L209 and L211)
and goes to the mixer. These BPFs are adjusted by variable
capacitors (D203,D204,D205 and D206). 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: 136 ~ 174MHz (M)
RF
ANT SW
AMP
TX: 136 ~ 174MHz (M)
TX
AMP
Fig. 1 Frequency configuration / 图 1 频率构成
ANT
BPF
ANT SW
TUNE
CF201
IC201
IF,MIX,DET
X1
Q1
TCXO
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
RX: 174.85 ~ 212.85MHz
(M)
RF PLL
MIC
AMP
VCO
AMP
2 . 接收部
接收部的频率构成如图 2 所示。
RF AMP
MIXER MCF
Q205 XF201
BPF Q204
TUNE 1st Local
IC301
IC302
AF VOL AF PA
AQUA
12.8MHz
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，D105 和 D106)，然后通过 BPF (L214 和 L213)，
并且被 RF 放大器 (Q205) 放大。
此信号通过 BPF (L209 和 L211) 然后进入混频。这些 BPF 被
可变电容器 (D203，D204，D205 和 D206) 调整。输入可变电
容 器 的 电 压 被 经 微 处 理 器
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
12.8MHz
MIC
IF AMP
Q203
SP
( I C 4 0 5 ) 的 电 压 输 出