Motorola ASTRO Digital Spectra Plus Detailed Service Manual page 8

vi
VHF Radio Specifications ........................................................................................................................ xlv
UHF Radio Specifications ........................................................................................................................xlvi
800 MHz Radio Specifications ................................................................................................................xlvii
Chapter 1 Introduction..........................................................................1-1
1.1 General...........................................................................................................................................1-1
1.2 Notations Used in This Manual ......................................................................................................1-2
Chapter 2 General Overview ................................................................2-1
2.1 Introduction.....................................................................................................................................2-1
2.2 Analog Mode of Operation .............................................................................................................2-2
2.3 ASTRO Mode of Operation ............................................................................................................2-2
2.4 Control Head Assembly..................................................................................................................2-2
2.4.1 Display (W3 Model) ...........................................................................................................2-2
2.4.2 Display (W4, W5, and W7 Models) ...................................................................................2-2
2.4.3 Display (W9 Model) ...........................................................................................................2-3
2.4.4 Vacuum Fluorescent Display Driver ..................................................................................2-3
2.4.5 Vacuum Fluorescent Voltage Source (W9 Model) ............................................................2-3
2.4.6 Controls and Indicators .....................................................................................................2-3
2.4.7 Status LEDs ......................................................................................................................2-3
2.4.8 Backlight LEDs ..................................................................................................................2-3
2.4.9 Vehicle Interface Ports ......................................................................................................2-4
2.4.10 Power Supplies .................................................................................................................2-4
2.4.11 Ignition Sense Circuits.......................................................................................................2-4
2.5 Power Amplifier ..............................................................................................................................2-5
2.5.1 Gain Stages.......................................................................................................................2-5
2.5.2 Power Control....................................................................................................................2-5
2.5.3 Circuit Protection ...............................................................................................................2-5
2.5.4 DC Interconnect ................................................................................................................2-5
2.6 Front-End Receiver Assembly........................................................................................................2-6
2.7 RF Board Basic ..............................................................................................................................2-6
2.8 Voltage-Controlled Oscillator..........................................................................................................2-6
2.8.1 VHF Radios .......................................................................................................................2-6
2.8.2 UHF and 800 MHz Radios ................................................................................................2-7
2.9 Command Board ............................................................................................................................2-7
2.10 ASTRO Spectra Vocoder/Controller Board ....................................................................................2-7
2.11 Radio Power...................................................................................................................................2-8
2.11.1 General..............................................................................................................................2-8
2.11.2 B+ Routing for ASTRO Spectra VOCON Board................................................................2-9
Chapter 3 Theory of Operation ............................................................3-1
3.1 RF Board ........................................................................................................................................3-1
3.1.1 General..............................................................................................................................3-1
3.1.2 Synthesizer........................................................................................................................3-3
3.1.2.1
3.1.2.2
3.1.2.3
3.1.2.4
September 5, 2008
Reference Frequency Generation ............................................................................3-3
First VCO Frequency Generation.............................................................................3-3
Programmable Reference Divider ............................................................................3-4
Phase Modulator ......................................................................................................3-5
Table of Contents
6881076C25-E