Circuit Description - Kenwood TK-2202L Service Manual

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Instruction manual (32 pages)

Table Of Contents

Table of Contents

1. Control Circuit

The control circuit consists of a microprocessor (IC405) and

its peripheral circuits. It controls the TX-RX unit. IC405 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 input.

(6) Transmitting tone and encode data.

1) Frequency Shift Circuit

The microprocessor (IC405) operates at a clock of

7.3728MHz. This oscillator has a circuit that shifts the

frequency by BEAT SHIFT SW (Q407,Q408).

A beat sound may be able to be evaded from generation if

"Beat Shift" is set to ON when it is generated in the internal

spurious transmission modulated sound of a transceiver.

IC405

XIN

XOUT

BSHIFT

Q407

H : OFF

L : ON

Fig. 1 Frequency shift circuit

2) Memory Circuit

Memory circuit consists of the CPU (IC405) and an EEPROM

(IC406). An EEPROM has a capacity of 8k bits that contains

the transceiver control program for the CPU and data such

as transceiver channels and operating features.

IC405

CPU

Fig. 2 Memory circuit

3) Low Battery Warning

The battery voltage is checked using by the microprocessor.

The transceiver generates a warning tone when the battery

voltage falls below the warning voltage (2) 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:

During reception, transceiver constantly checks the battery

level. When the battery level drops near to 5.9V, the red

LED blinks and low battery warning tone is generated.