TK-3148
11
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.
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.
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。
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
MIX, DET, IF
SW
Q204
DM
DM
IC300 (2/2)
AF AMP
5
DE-
EMP
MUTE
EXP
IC500
2
HPF
LPF
HPF
BEF
VOL
IC307
IC305 (2/2)
AF AMP
41
VC1
VC2
Q308
SSW
INT.
SP
EXT.
SP
2nd local
OSC
X200
AF AF
SW
IC313
AF PA
ANT
SW
L110~
112
L215,217
BPF
D102~
105
Q207
RF AMP
ANT
Q206
1st MIX
Q205
1st IF
L209~211
BPF
XF200
MCF
1st Local
OSC (PLL)
1
CF1: Wide
CF2: Narrow
Q201
IC200
Q202
AFOUT
5R
R213
R210
CF201
CF200
D202
D203
R208
R216
R211
C206
C210
MIXOUT
AFOUT
QUAD
IFOUT
IFIN
C221
R255
R221
CD200
R264
R256
W/N
5CNS
R222
Fig. 2 Receiver section /
图 2 接收部构成
Fig. 3 Wide/Narrow switching circuit /
图 3 宽 / 窄转换电路
CIRCUIT DESCRIPTION /
电路说明