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Chapter 4: i

6881091C63-A

Chapter 4: VHF (136-174 MHz) 1-25W

Service Information

Table of Contents

Section 1 Model Charts and Technical Specifications

1.0 VHF (136-174 MHz) 1-25W Model Charts........................................................4:1-1

1.1 CDM Series Model Chart ............................................................................4:1-1

1.2 PRO Series Model Chart.............................................................................4:1-2

2.0 Technical Specifications ...................................................................................4:1-2

Section 2 Theory of Operation

1.0 Introduction .......................................................................................................4:2-1

2.0 VHF (136-174 MHz) 1-25W Receiver Front-End..............................................4:2-1

2.1 Receiver Front-End .....................................................................................4:2-1

2.2 Front-End Bandpass Filters and Pre-Amplifier............................................4:2-2

2.3 First Mixer and High Intermediate Frequency (IF).......................................4:2-2

2.4 Low Intermediate Frequency (IF) and Receiver Back-End .........................4:2-2

3.0 VHF (136-174 MHz) 1-25W Transmitter Power Amplifier (PA) 25W ................4:2-3

3.1 First Power Controlled Stage ......................................................................4:2-3

3.2 Power Controlled Driver Stage....................................................................4:2-4

3.3 Final Stage ..................................................................................................4:2-4

3.4 Directional Coupler......................................................................................4:2-4

3.5 Antenna Switch ...........................................................................................4:2-5

3.6 Harmonic Filter ............................................................................................4:2-5

3.7 Power Control..............................................................................................4:2-5

4.0 VHF (136-174 MHz) 1-25W Frequency Synthesis ...........................................4:2-5

4.1 Reference Oscillator....................................................................................4:2-6

4.2 Fractional-N Synthesizer .............................................................................4:2-6

4.3 Voltage Controlled Oscillator (VCO)............................................................4:2-7

4.4 Synthesizer Operation.................................................................................4:2-8

Section 3 Troubleshooting Charts

1.0 Troubleshooting Flow Chart for Receiver .........................................................4:3-1

2.0 Troubleshooting Flow Chart for 25W Transmitter.............................................4:3-3

3.0 Troubleshooting Flow Chart for Synthesizer.....................................................4:3-6

4.0 Troubleshooting Flow Chart for VCO................................................................4:3-7

Motorola CDM Series Service Manual

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