Abell A-510T, Service Manual

Page: 19 / 53

A-510T（UHF）Ver1.0
19/53
with the maximum frequency deviation by audio processor U301, and it is modulated by U302.
（ 6 ） Wide/narrow band conversion
We can use programming software to enable wide/narrow band to set that of various channels, and the
wide/narrow is converted by U302 SCT3258TD baseband processor.
（
7
）
QT/DQT code
QT data is produced by audio baseband processor U302; the waveform of signal is optimized by CR low pass,
then it enters U301 for modulation; QT frequency deviation is adjusted by (U301) chip.
DQT data is produced by audio baseband processor U302; the waveform of signal is optimized by CR low pass,
then it enters X2 clock crystal for modulation; DQT frequency deviation is adjusted by audio baseband processor
U302.
（
8
）
VOX
Microphone (M1) produces signal, and U307 signal level will determine whether it is above or below the default,
then the produced high/low level enter the VOX DET port of microprocessor U300. The microprocessor U300 can
determine whether to enable transmission by detecting the input high /low level. (Refer to figure 5)
SP
IF AMP
DET
DET
LPF
U9 RD1846S FM IF
LPF HPF
TDA2822
U306
Q302
Power SW
QT/DQT
U300
CPU
BU
SY
FM_MUTE
AF
C
O
TI
Chart 5 AF Amplifier and Squelch
W/N
De_emphasis
U302
SCT3258TD
U9 RD1846S FM IF
VCO
U307
MIC
NJM2904V
M1
（
9
）
Voice prompt
Chinese/English voice broadcast signal can be produced by U316, and the signal through VR1 volume control
circuit, then being amplified through audio power amplification U306 can drive speaker.(Chinese/English voice
broadcast signal includes broadcast of battery level, alarm sound, broadcast of power channel)
5.5 Power
VCC7.5V enters through J1; 5V outputs constant voltage by U313, then it outputs A3V3 through U309 to give
U300.CPU and power supply, and U310 outputs constant voltage RF3V3, which is a power supply for U9 RD1846S.
When two way radio works in transmission mode, the microprocessor is U300/TX_CTL. It controls U315 to output
5T to supply power for transmission circuit. When it works in receiving mode, the microprocessor U300/RX_CTL
will output high level to control U314
（ 5R ） to supply power for receiving circuit.(Refer to figure 6)