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The second IF signal is passed through the ceramic fi lter
(CF200; Wide, CF201; Narrow) to more remove the adjacent
channel signal. The fi ltered second IF signal is amplifi ed by
the limiting amplifier and demodulated by the quadrature
detector with ceramic discriminator (CD200). The demodu-
lated signal is routed to the audio circuit.
ANT
D102~
L110~
L215,217
105
112
BPF
ANT
SW
2
IC500
HPF
LPF
HPF
5
3-3. Wide/Narrow switching circuit
Narrow and Wide settings can be made for each channel
by switching the ceramic fi lters CF200 (Wide), CF201 (Nar-
row).
The WIDE (high level) and NARROW (low level) data is
output from IC311 pin 14.
Regardless of NARROW or WIDE band selection, signals
always pass through the fi lter, CF200.
When the WIDE band is selected, Q201 is turned ON,
then D202 and D203 are turned OFF.
So, the signal does not pass through the filter CF201.
When the NARROW band is selected, Q201 is turned OFF,
then D202 and D203 are turned ON. So, the signal passes
through the fi lters, CF200 and CF201.
Q202 turns on/off with the Wide/Narrow data and the
IC200 detector output level is changed to maintain a con-
stant output level during wide or narrow signals.
CIRCUIT DESCRIPTION /
Q206
XF200
Q207
L209~211
RF AMP
BPF
1st MIX
1st Local
OSC (PLL)
1
BEF
DE-
MUTE
EXP
EMP
Fig. 2 Receiver section / 图 2 接收部构成
电路说明
第二中频信号通过陶瓷滤波器 ( C F200: 宽，C F201: 窄 ) 继
续消除相邻信道的信号。经滤波的第二中频信号被限幅放大
器放大并被带有陶瓷鉴频器 ( C D200) 的正交鉴频器进行解调。
解调后的信号进入音频电路。
Q205
MCF
1st IF
IC200
MIX, DET, IF
CF1: Wide
X200
2nd local
CF2: Narrow
OSC
IC305 (2/2)
IC307
AF AMP
AF AF
VOL
41
3-3. 宽 / 窄转换电路
可以通过开启陶瓷滤波器 CF200( 宽 )，CF201( 窄 ) 对每一
个信道进行窄宽设定。
IC311 的管脚 14 输出宽 ( 高电平 ) 和窄 ( 低电平 ) 信号。
无论选用宽还是窄带，信号都要通过滤波器 CF200。
当选用 WIDE 带宽时，D202 和 D203 关断。
因 此， 信 号 不 通 过 滤 波 器 C F201。 当 选 用 N A R R O W 带 宽
时，Q201 关断，D202 和 D203 打开。因此，信号通过滤波器
CF200 和 CF201。
Q202 伴随着宽 / 窄数据而接通 / 断开，I C200 检测器输出
电平经常变化用来维持宽或窄信号过程中的恒定输出电平。
IC200
Q201
CF200
Fig. 3 Wide/Narrow switching circuit /
图 3 宽 / 窄转换电路
TK-3148
IC300 (2/2)
AF AMP
Q204
SW
DM
DM
IC313
AF PA
Q308
SW
VC1
SSW
EXT.
VC2
R255
R264
Q202
R221
R256
CD200
5CNS
R222
AFOUT
CF201
D202
D203
INT.
SP
SP
W/N
11
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