Modb/Vstby Supply; Audio/Signaling; Uhf1 Transmitter; Figure 2-3. Transmitter Block Diagram - Motorola PR860 Detailed Service Manual

2-4
2.3.2

MODB/VSTBY Supply

The supply to the MODB/VSTBY pin varies depending on the conditions listed in
Radio On
Radio Off
Primary battery removed
2.3.3

Audio/Signaling

The audio/signalling/filter/companding IC (ASFIC) and the audio power amplifier
page 2-3) form the main components of the audio/signalling section of the controller board. Inputs
include a 16.8 MHz clock from the synthesizer, recovered audio and squelch, MCU control signals,
and external or internal microphones. Outputs include a microprocessor clock (CLK), modulator
output to the synthesizer, and amplified audio signals to an internal or external speaker.
2.4

UHF1 Transmitter

From VCO
The UHF transmitter consists of the following basic circuits as shown in
• Power amplifier (PA).
• Antenna switch/harmonic filter.
• Antenna matching network.
• Power control integrated circuit (PCIC).
Table 2-4. MODB/VSTBY Supply Modes
Condition
Vddd supply voltage via CR411
• Vddd turned off
• Q416 gate pulled low by R462
• Q416 switched on
• U410 supplies 3.2V to MODB_VSTBY
• Vddd turned off
• Q416 gate pulled low by R462
• Q416 switched on
• Lithium-ion battery provides 3.2V to MODB_VSTBY
P C I C
Vcontrol
P A
Driver

Figure 2-3. Transmitter Block Diagram

Theory of Operation: UHF1 Transmitter
Circuit Operation
Vcontrol
Antenna Switch/
PA-Final
Harmonic Filter/
Stage
Matching Network
Table 2-4.
(Figure 2-2 on
Antenna
Jack
Figure 2-3.