Chapter 1 Theory Of Operation; Introduction; Transmitter; General - Motorola GP344 Detailed Service Manual

1.0

Introduction

This Chapter provides a detailed theory of operation for the UHF circuits in the radio. Schematic
diagrams and board layout diagrams are included in Chapter 4 in this Section of the manual.
2.0

Transmitter

From VCO
2.1

General

(Refer to Figure 1-1)
The UHF transmitter contains five basic circuits:
1. Power Amplifier
2. Antenna Switch
3. Harmonic Filter
4. Antenna Matching Network
5. Power Control Integrated Circuit (PCIC)
2.1.1 Power Amplifier
The power amplifier consists of two devices:
1. 9Z67 LDMOS driver IC (U101) and
2. PRF1507 LDMOS PA (Q110)
The 9Z67 LDMOS driver IC contains a 2 stage amplification with a supply voltage of 7.3V.
P C I C
Vcontrol
P A
Driver
Figure 1-1 Transmitter Block Diagram
THEORY OF OPERATION
Vcontrol
Antenna Switch/
PA-Final
Harmonic Filter/
Stage
Matching Network
Chapter 1
Antenna
Jack