Motorola EP450 Service Manual page 5

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Chapter 4 VHF Theory Of Operation ................................................... 4-1
4.1 Introduction .................................................................................................................................... 4-1
4.2 VHF Receiver................................................................................................................................. 4-1
4.2.1 Receiver Front-End........................................................................................................... 4-1
4.2.2 Receiver Back-End ........................................................................................................... 4-2
4.3 VHF Transmitter............................................................................................................................. 4-3
4.3.1 Transmit Power Amplifier .................................................................................................. 4-3
4.3.2 Antenna Switch ................................................................................................................. 4-3
4.3.3 Harmonic Filter.................................................................................................................. 4-3
4.3.4 Antenna Matching Network............................................................................................... 4-4
4.3.5 Power Control ................................................................................................................... 4-4
4.4 VHF Frequency Generation Circuitry............................................................................................. 4-4
4.4.1 Fractional-N Synthesizer................................................................................................... 4-5
4.4.2 Voltage Controlled Oscillator (VCO) ................................................................................. 4-6
4.5 Keypad........................................................................................................................................... 4-7
Chapter 5 VHF Troubleshooting Tables ............................................. 5-1
5.1 Troubleshooting Table for Receiver............................................................................................... 5-1
5.2 Troubleshooting Table for Synthesizer .......................................................................................... 5-3
5.3 Troubleshooting Table for Transmitter........................................................................................... 5-4
5.4 Troubleshooting Table for Board and IC Signals ........................................................................... 5-6
Chapter 6 VHF Schematic Diagrams, Overlays, and Parts Lists...... 6-1
6.1 Introduction .................................................................................................................................... 6-1
6.1.1 Notes For All Schematics and Circuit Boards ................................................................... 6-1
6.1.2 Six Layer Circuit Board ..................................................................................................... 6-3
6.2 Speaker and Microphone Schematic ............................................................................................. 6-3
6.2.1 Speaker and Microphone Parts List.................................................................................. 6-3
Figure 6-3. VHF (146-174 MHz) Radio Circuit Block Interconnect Diagram....................................... 6-5
Figure 6-4. VHF (146-174 MHz) Receiver Front End Schematic Diagram ......................................... 6-6
Figure 6-5. VHF (146-174 MHz) Receiver Back End Schematic Diagram ......................................... 6-7
Figure 6-6. VHF (146-174 MHz) Synthesizer Schematic Diagram ..................................................... 6-8
Figure 6-7. VHF (146-174 MHz) Voltage Controlled Oscillator Schematic Diagram .......................... 6-9
Figure 6-8. VHF (146-174 MHz) Transmitter and Power Control Schematic Diagram ..................... 6-10
Figure 6-9. VHF (146-174 MHz) Controller Interconnect Schematic Diagram.................................. 6-11
Figure 6-10. VHF (146-174 MHz) Microprocessor Circuitry Schematic Diagram ............................... 6-12
Figure 6-11. VHF (146-174 MHz) Audio Circuitry Schematic Diagram............................................... 6-13
Figure 6-12. VHF (146-174 MHz) DC Regulation Schematic Diagram.............................................. 6-14
Figure 6-13. VHF (146-174 MHz) Keypad Board Schematic Diagram ............................................... 6-15
Figure 6-14. VHF (146-174 MHz) Board Component Side View ........................................................ 6-16
Figure 6-15. VHF (146-174 MHz) Board Solder Side View ................................................................ 6-17
Figure 6-16. VHF (146-174 MHz) Keypad Board................................................................................ 6-18
VHF (146-174 MHz) Radio Parts List .................................................................................................... 6-19
VHF (146-174 MHz) Keypad Board Parts List....................................................................................... 6-22
November 24, 2003
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