Kenwood TK-2302 Service Manual page 12

TK-2302/2302
■ Frequency Shift Circuit
The MCU (IC306) operates at a clock of 14.746 MHz. This
oscillator has a circuit that shifts the frequency by BEAT
SHIFT SW (Q305, Q306).
A beat sound may be able to be evaded from generation
if "Beat Shift" is set to ON when it is generated in the inter-
nal spurious transmission modulated sound of a transceiver.
IC306
MCU
XOUT
Q305
Fig. 8 Frequency shift circuit
■ Memory Circuit
Memory circuit consists of the MCU (IC306) and an EE-
PROM (IC305). An EEPROM has a capacity of 16k bits that
contains the transceiver control program for the MCU and
data such as transceiver channels and operating features.
IC306
MCU
Fig. 9 Memory circuit
■ Low Battery Warning
The battery voltage is checked using by the MCU. The
transceiver generates a warning tone when it falls below
the warning voltage shown in the table.
1) The red LED blinks when the battery voltage falls below
the voltage (1) shown in the table during transmission.
Note: The transceiver checks the battery voltage during
reception even when, in the FPU, the Battery Warning
status function is set to "On TX" (default setting).
However, the LED does not blink during reception. Dur-
ing transmission, the LED blinks to generate the warning
tone of a low battery voltage.
2) The transceiver immediately stops transmission when
the battery voltage falls below the voltage (2) shown in
the table. A message tone beeps while the PTT switch is
released.
Ni-Cd Battery
(1) 6.2V
(2) 5.9V
12
V /2306
( )
CIRCUIT DESCRIPTION
BSHIFT
XIN
X301
Hi: ON
Low: OFF
Q306
IC305
EEPROM
Ni-MH Battery Li-ion Battery
6.2V 6.2V
5.9V 5.9V
R301
SB
Fig. 10 Low battery warning
7. Control System
Keys and channel selector circuit. The signal from the
keys and channel selector are directly input to the MCU, as
shown in Fig. 11.
Channel
selector
62
EN1
IC306
61
MCU
EN2
60
EN3
59
EN4
58
EN5
Fig. 11 Control system
IC306
66
MCU
55
PTT
PTT
SW
56
SIDE1
SW1
57
SIDE2
SW2