TS-5700
12
CIRCUIT DESCRIPTION
•
Signal-Strength Meter Circuit
In modes other than FM, the AGC voltage is inverted
and amplified by operational amplifier IC1: NJM2904M.
This output is used as the signal strength meter volt
age. In FM mode, the level detection output from IC7:
KCD10 is used. The signal strength meter voltage in
each mode is switched by analog switch IC4:
BU4066BCFV and output to the control unit.
AGC
•
Squelch Circuit
In FM mode, the noise detection voltage (FSQL) out
put from IC7: KCD10 is sent to the control unit. In
modes other than FM, the signal strength meter volt
age is sent to the control unit. It is compared with the
voltage proportional to the angle of the SOL VR to con
trol squelch opening and closing. The microcomputer
controls the delay time and hysterisis.
SQ
AM
SB
AMB DET SCB DET
1
-----------------------------------
]
E
IF
SC
IC15: KCD11
....
a:
IC7: KCD10
Q
a:
N
0
U
d
�
OO
�
U
U'J
U'J
C30
�
5
,
R2SS
FM
DET
FMS
CAR
E
SF
AGS
Fig. 8 AGC and S-meter circuits
(For control unit)