Motorola CDM1250 Service Manual

Section 6: i
6881091C63-F
Section 6: UHF Band 2 (450–512/527 MHz) 1–25W
Service Information
Table of Contents
Chapter 1 Model Charts and Technical Specifications
1.0 UHF Band 2 (450–512/527 MHz) 1–25 W Model Charts .................................6:1-1
1.1 CDM Series Model Chart ............................................................................6:1-1
1.2 PRO Series Model Chart.............................................................................6:1-2
2.0 Technical Specifications ...................................................................................6:1-2
Chapter 2 Theory of Operation
1.0 Introduction.......................................................................................................6:2-1
2.0 UHF Band 2 (450–512/527 MHz) 1–25W Receiver Front-End.........................6:2-1
2.1 Receiver Front-End .....................................................................................6:2-1
2.2 Front-End Bandpass Filters and Pre-Amplifier............................................6:2-2
2.3 First Mixer and High Intermediate Frequency (IF).......................................6:2-2
2.4 Low Intermediate Frequency (IF) and Receiver Back-End .........................6:2-3
3.0 UHF Band 2 (450–512/527 MHz) 1–25 W Transmitter Power Amplifier
(PA) 25 W .........................................................................................................6:2-3
3.1 First Power Controlled Stage ......................................................................6:2-4
3.2 Power Controlled Driver Stage....................................................................6:2-4
3.3 Final Stage ..................................................................................................6:2-4
3.4 Directional Coupler......................................................................................6:2-5
3.5 Antenna Switch ...........................................................................................6:2-5
3.6 Harmonic Filter............................................................................................6:2-5
3.7 Power Control..............................................................................................6:2-5
4.0 UHF Band 2 (450–512/527 MHz) 1–25 W Frequency Synthesis .....................6:2-6
4.1 Reference Oscillator....................................................................................6:2-6
4.2 Fractional-N Synthesizer.............................................................................6:2-6
4.3 Voltage Controlled Oscillator (VCO)............................................................6:2-8
4.4 Synthesizer Operation.................................................................................6:2-9
Chapter 3 Troubleshooting Charts
1.0 Troubleshooting Flow Chart for Receiver .........................................................6:3-1
2.0 Troubleshooting Flow Chart for 25 W Transmitter............................................6:3-3
3.0 Troubleshooting Flow Chart for Synthesizer.....................................................6:3-6
4.0 Troubleshooting Flow Chart for VCO................................................................6:3-7
5.0 Troubleshooting Flow Chart for PassPort.........................................................6:3-8

Motorola CDM1250 Specifications

General

Display	Alphanumeric
IP Rating	IP54
Frequency Range	VHF: 136-174 MHz, UHF: 403-470 MHz
Signaling	PL, DPL, MDC1200, Quick Call II
Operating Temperature	-22°F to +140°F (-30°C to +60°C)
Power Output	VHF: 1-25W; UHF: 1-25W