Kenwood TK-3301 Service Manual page 9

(2/2) controls the VG of the RF power amplifier and drive
amplifi er to make both voltages the same.
The change of power high/low is carried out by the
change of the reference voltage.
■ Encode Signaling
• QT/DQT
QT/DQT data of the QTTCXO Line is output from pin 14
of the MCU. The signal passes through a low-pass CR fi lter
and goes to the TCXO (X1).
The QT/DQT data of the QTVCO Line is output from pin
15 of the MCU. The signal passes through a low pass CR fi l-
ter, mixes with the audio signal, and goes to the VCO modu-
lation input. TX deviation is adjusted by the MCU.
5. Power Supply
There are four 5V power supplies in the transceiver: 5M,
5C, 5R, and 5T. 5M for MCU is always output while the
power is on. 5M is always output, but turns off when the
power is turned off to prevent malfunction of the MCU.
5C is a common 5V and is output when SAVE is not set
to OFF.
5R is 5V for reception and output during reception.
5T is 5V for transmission and output during transmission.
6. Control Circuit
The control circuit consists of a MCU (IC306) and its
peripheral circuits. It controls the TX-RX unit. IC306 mainly
performs the following:
1) Switching between transmission and reception by the
PTT signal input.
2) Reading system, group, frequency, and program data
from the memory circuit.
3) Sending frequency program data to the PLL.
4) Controlling squelch on/off by the DC voltage from the
squelch circuit.
5) Controlling the audio mute circuit by the decode data in-
put.
6) Transmitting tone and encode data.
■ 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
X301
Hi: ON
Low: OFF
Q305
Fig. 7 Frequency shift circuit
CIRCUIT DESCRIPTION
BSHIFT
XIN
Q306
■ 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. 8 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
R301
SB
Fig. 9 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. 10.
Channel
selector
62
EN1
IC306
61
MCU
EN2
60
EN3
59
EN4
58
EN5
Fig. 10 Control system
TK-3301
IC305
EEPROM
Ni-MH Battery Li-ion Battery
6.2V 6.2V
5.9V 5.9V
IC306
66
MCU
55
PTT
PTT
SW
56
SIDE1
SW1
57
SIDE2
SW2
9