Main Board - Motorola APX 1000 Detailed Service Manual

Theory of Operation: Main Board
3.1

Main Board

The main board performs the transmitter and receiver functions necessary to translate between
voice and data to modulated radio-frequency (RF) carrier at the antenna. The main board contains
all the radio's RF circuits for the following major components:
• Receiver
• Transmitter
• Frequency Generation Unit (FGU)
• Controller
Figure 3-2, Figure
transceiver block diagrams.
Termination
GPS
Rev
Power
Detector
LNA
VHF
Figure 3-2. Transceiver (VHF) Block Diagram (Power and Control Omitted)
3-3, Figure 3-4 and
Batt. DC Supply
Current
Current
Sense
Sensor
Circuit
DC Supply to FET PA & Driv. Amp.
Harmonic
Filter
coupler
o
15dB Step Attn
16.8MHz
TRIDENT IC
PRESCALAR
BUFFER
16.8MHz
BUFFER
VHF
Figure 3-5 illustrates the VHF, UHF1, UHF2 and 700/800 MHz
Power Control Voltage (Vctrl)
Antenna Switch
FET
VHF
LOOP
RX VCO
FILTER
PRE
TX VCO
BUFFER
IF Filter
Mixer
Indicates Sub-shield
Driver
Amplifier
TX
TX
BUFFER
TX LO
RX
RX LO
RX SSI Data
Abacus
RX SSI Frame Sync
2nd
LO
3-3
FGU
Transmitter
Receiver
RX SSI Clock