Motorola ASTRO Digital Spectra Service Manual page 4

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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 Reference Frequency Generation............................................................................ 3-3
3.1.2.2 First VCO Frequency Generation ............................................................................ 3-3
3.1.2.3 Programmable Reference Divider............................................................................ 3-4
3.1.2.4 Phase Modulator...................................................................................................... 3-5
3.1.2.5 Loop Filter ................................................................................................................ 3-5
3.1.2.6 Auxiliary Control Bits................................................................................................ 3-5
3.1.2.7 Second VCO ............................................................................................................ 3-6
3.1.2.8 Power Distribution.................................................................................................... 3-6
3.1.3 Receiver Back-End ........................................................................................................... 3-6
3.1.3.1 First IF...................................................................................................................... 3-6
3.1.3.2 ABACUS II IC........................................................................................................... 3-7
3.2 Command Board............................................................................................................................ 3-8
3.2.1 Microcontroller and Support ICs ....................................................................................... 3-8
3.2.2 Serial Input/Output IC ....................................................................................................... 3-8
3.2.3 Power-Up/-Down Sequence ............................................................................................. 3-9
July 1, 2002
Table of Contents
68P81076C25-C