Service Manual

Page 4.4
3 ~ TECHNICAL DESCRIPTION
Directional
Coupler
TX VCO
Q602
VCO
Buffer
Q604/
Q605
TX/RX
Switch
D610/
Q611
TX PA U500
Antenna
Switch
D580/
D540/
D541
Antenna
Switch
Control
Q541/
Q542
Power
Control
Comparator
U520A
Antenna
Filter
L582/
L584/L585
TX VCO
Switch
Q603
LO1_RX
Power
Control
Detector
D510
Integrator
R308/C307
PWM TX Power
Set from PLA
ADC/DAC/
CODEC U820
TX_MOD
From PLA/DSP
RX/TX AF
Switch
U800A
Q
I
TX/RX AF Control
From PLA
Switch
U800C
Internal MIC/ External
Audio Control From PLA
Internal Micropone
External Accessory Audio
PA_ON
Current
Sense
U520-B
TX Current Sense to PLA
13V8_UNSW From L8
Audio
Gate
U302-B
TX Buffer
Amp
Q550/
Q560
DATA_EN
Alert Tones to U850
from PLA
TX_CURRENT
Thermal
Shut Back
R532
TX_PWR
MOD_SW
TX_MODE
To RX Mixer
Figure 4-2 VHF/UHF Transmitter Block Diagram