Squelch Circuit - Kenwood TM-V7A Service Manual

CIRCUIT DESCRIPTION
Squelch Circuit
The squelch control angle is read into the panel section
microprocessor and converted from analog to 6-bit digital.
For adjustment mode, on the main unit side, the threshold
ievel signal is received and the SQ voltages (SQV and
SQU) at that time are stored into the microprocessor. The
Shift Register Circuits
The TX-RX units have two shift registers (IC19 and
IC20: BU2090FS) and carry out the control below.
@1C19 Control
microprocessor calculates the squelch release voltage
using this voltage as the reference. This voltage and the
panel section squelch control voltage are compared and the
TM-V7A/E
squelch switched on and off.
@1C20 Conirol
Pin No. Name Function
1 Vss GND
2 DATA Serial data input
3 CLOCK Clock
4 VRX 144 8RSW
5 UTX 430 8TSW.
6 VIX 144 8TSW.
7 AM2 AGC control
8 AMi AGC control
9 V14RSW 144 band reception power control
10 V43RSW Sub 430 band reception power control
11 VRX 430 8RSW
12
13 U43RSW 430 band reception power control
14
15 Ui4RSW Sub 144 band reception power control
VDD 5V
— o
Pin No. Name Function
1 Vss GND
2 __| DATA Serial data input
3 CLOCK Clock
4
5 AM SW AM switching
6
7
8 USHIFT UHF VCO shift
9 FAN Fan control
10 VPLL VCO high-speed lock (VHF)
11 VSHIFT VHF VCO shift
12 AGC AGC switch
13 VAIP VHF AIP switch
14 UAIP UHF AIP switch
15 UPLL VCO high-speed lock (UHF)
16 VDD 5V