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TK-3312/3317
15
RF
AMP
Baseband
IC
VCO
PLL
MCU
IC820
PL_STB,PL_CLK,PL_DAT
IC1
PL_UL
17
10
21
7
BUFF
SW
LPF
To mixer
VC
Q9
BUFF
Q8
TCXO
X1
IC812
SW
To
RF AMP
TX
(TX: High)
D18
D17
Q2
CV
Fig. 6 PLL block diagram
5. Control Circuit
The control consists of the MCU (IC820) and its peripher-
al circuits. It controls the TX-RX unit. IC820 mainly performs
the following;
1) Switching between transmission and reception by PTT
signal input.
2) Reading channel information, frequency, and program
data from the memory circuit.
3) Sending frequency program data to the PLL.
4) Controlling squelch on/off via the DC voltage from the
squelch circuit.
5) Controlling the audio mute circuit via the decode data in-
put.
6) Transmitting tone and encode data.
5-1. Frequency Shift Circuit
The MCU (IC820) and baseband IC (IC812) operates at
a clock frequency of 19.2MHz. The oscillator circuit has the
baseband IC. This oscillator has a circuit that shifts the fre-
quency via Beat shift switch (Q806).
A beat sound may be able to be evaded form generation
if “Beat Shift“ is set to ON when it is generated in the in-
ternal spurious transmission modulated sound of the trans-
ceiver.
IC812
Baseband IC
H: OFF
L: ON
MCU
XIN
X802
39
40
XOUT
XIN
Q806
C846
R857
MCU
BSHIFT
Fig. 7 Frequency shift circuit
5-2. Memory Circuit
The Memory circuit consists of the MCU (IC820) and
EEPROM (IC810). The EEPROM has a capacity of 512k bits
and stores the channel information, the last channel data,
the scan on status, and other parameters.
■
EEPROM
Note:
The EEPROM stores tuning data (Deviation, Squelch,
etc.).
Realign the transceiver after replacing the EEPROM.
MCU
EEPROM
IC820
IC810
Fig. 8 Memory circuit
5-3. Low Battery Warning
The battery voltage is monitored by the MCU (IC820 pin
63: BATT). When the battery voltage falls below the volt-
age set by the Low Battery Warning adjustment, the red
LED blinks, notifying the operator that it is time to replace
the battery (when the always option (default setting) under
the Battery Warning function in the FPU is selected). If the
battery voltage falls bellow 5.9V, the transceiver does not
transmit and the warning tone beeps while the PTT switch
is pressed.
Low battery warning
Battery status
The red LED blinks during trans-
mission.
The battery voltage is low but
the transceiver is still usable.
The red LED blinks and the
warning tone beeps while the
PTT switch is pressed.
The battery voltage is lowand
the transceiver cannotbe used
to make calls.
63
IC820
MCU
BATT
R824
SB
R829
Fig. 9 Low battery warning
CIRCUIT DESCRIPTION