Service Manual

Detect of external PTT, MONI and VOX

Detect of PLL unlock (UL)

Detect of VOX ON level

Detect of battery power alarm

Detect of enabling and checking external remote speaker microphone

3. Data Transfer and Process

EEPROM data initiation

Programming data transfer

Encoding process of channel selector knob

Signalling encoding and decoding

Data transfer of baseband processing chip (PLL)

Power Supply Process

Block Diagram for the Circuit

Q611

power management

Vin

VSS

Vout

---

7.2V

U606

L604

601s

SAVE

FMMT717FMMT717

Q612

UPA572T

Q610

TXC

V-TX

POWER-SAVE

Figure 10

After the radio is powered on, the battery voltage is provided to the RF power amplifier and audio

power amplifier to meet the requirements of sufficient power amplification after filtered by L604 and

C682. Another path is input with the regulator IC (U606) of 5V and outputs voltage of VCC_5V for

use by MCU and the baseband processing chip after regulated. Because the radio works under the

half duplex mode, it is required to control the Tx and Rx power supply alternately. To meet the

requirement of the battery save mode, MCU should output a pulse signal with fixed duty factor