Frequency Configuration; Receiver System; Front End (Rf Amplifi Er) Circuit; Circuit Description - Kenwood TK-2317 Service Manual

CIRCUIT DESCRIPTION / 电路说明
1. Frequency Confi guration
The receiver utilizes double conversion. The first IF is
49.95MHz and the second IF is 450kHz. The fi rst Local os-
cillator is supplied from the PLL circuit.
The PLL circuit in the transmitter generates the neces-
sary frequencies.
TX/RX: 136~174MHz
ANT
ANT
SW
TX
AMP
Fig. 1 Frequency confi guration /

2. Receiver System

The receiver system is shown in Figure 2.
ANT
Q407
BPF RF AMP
ANT
SW
BPF1
2-1. Front End (RF Amplifi er) Circuit
The signal coming from the antenna passes through the
transmit / receive switching diode circuit (D201, D202, D203
and D204) and a BPF (L418 and L419), and is then ampli-
fi ed by the RF amplifi er (Q407).
The resulting signal passes through a BPF (L419, L418,
L416 and L414) and goes to the mixer. These BPFs are ad-
justed by variable capacitance diodes (D408, D407, D405
and D404). The input voltage to the variable capacitance
diodes is a regulated voltage output from the DC amplifi er
(IC811).
1st MIX MCF
RF
AMP
49.95MHz
185.95~
223.95MHz
RF
AMP
136~174MHz
Q406
BPF 1st MIX XF401
MCF
BPF1 1st Local
Fig. 2 Receiver system /
1. 频率构成
接收部采用二次变频超外差方式。第一中频为 49.95M Hz，
第二中频为 450kHz。第一本振频率信号由锁相环电路提供。
发射部由锁相环电路直接产生所需的频率。图 1 显示各种
频率。
CF
450kHz
IF AF
System baseband
50.4MHz
X3
TCXO 16.8MHz
multiply
PLL
VCO
图 1 频率构成
2. 接收部系统
接收部系统的如图 2 所示。
CF402 CF401
Q405
IF AMP
IC401
IF,MIX,DET
Q403
X3 multiply
2nd Local
图 2 接收部系统
2-1. 前级 ( 射频放大器 ) 电路
从天线接收的信号进入发送 / 接收转换开关二极管电路
(D201、D202、D203 和 D204)，然后通过 B PF (L418 和 L419)，
并且被射频放大器 (Q407) 放大。
此信号通过 BPF(L419,L418,L416 和 L414) 然后进入混频。
这些 BPF 被可变电容器 ( D408, D407,D405 和 D404) 调整。输
入可变电容器的电压被经直流放大器 (IC811) 的电压输出调
整。
TK-2317
SP
AF
AMP
MIC
MIC
AMP
IC815
IC812 AF PA SP
AF
baseband
X1
TCXO
16.8MHz
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