Motorola ASTRO Digital Spectra Service Manual page 6

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3.5.2.9 Doubler .................................................................................................................. 3-50
3.5.2.10 Synthesizer Feedback ........................................................................................... 3-50
3.5.2.11 Second Buffer ........................................................................................................ 3-50
3.5.2.12 Receive/Transmit Switch ....................................................................................... 3-50
3.5.3 800 MHz Band ................................................................................................................ 3-50
3.5.3.1 General .................................................................................................................. 3-50
3.5.3.2 Super Filter 8.6 V ................................................................................................... 3-50
3.5.3.3 VCO ....................................................................................................................... 3-50
3.5.3.4 Receive Mode-AUX 1* and AUX 2* High............................................................... 3-51
3.5.3.5 Transmit Mode-AUX 1* High; AUX 2* Low ............................................................ 3-51
3.5.3.6 TalkAround Mode-AUX 1* Low; AUX 2* Low......................................................... 3-51
3.5.3.7 VCO Buffer............................................................................................................. 3-51
3.5.3.8 First Buffer Circuit .................................................................................................. 3-51
3.5.3.9 Doubler .................................................................................................................. 3-51
3.5.3.10 Second Buffer ........................................................................................................ 3-52
3.5.3.11 K9.4 V Switch......................................................................................................... 3-52
3.6 Receiver Front-End...................................................................................................................... 3-53
3.6.1 VHF Band ....................................................................................................................... 3-53
3.6.1.1 General .................................................................................................................. 3-53
3.6.1.2 Theory of Operation ............................................................................................... 3-53
3.6.2 UHF Band ....................................................................................................................... 3-53
3.6.2.1 General .................................................................................................................. 3-53
3.6.2.2 Theory of Operation ............................................................................................... 3-54
3.6.3 800 MHz Band ................................................................................................................ 3-54
3.6.3.1 General .................................................................................................................. 3-54
3.6.3.2 Theory of Operation ............................................................................................... 3-54
3.7 Power Amplifiers .......................................................................................................................... 3-55
3.7.1 VHF Band Power Amplifiers ........................................................................................... 3-55
3.7.1.1 High-Power Amplifier ............................................................................................. 3-55
3.7.1.1.1 Transmitter...................................................................................................... 3-55
3.7.1.1.2 Antenna Switch and Harmonic Filter............................................................... 3-56
3.7.1.1.3 Power Control Circuitry ................................................................................... 3-57
3.7.1.2 25/10-Watt Power Amplifier ................................................................................... 3-59
3.7.1.2.1 Antenna Switch and Harmonic Filter............................................................... 3-60
3.7.1.2.2 Power Control Circuitry ................................................................................... 3-60
3.7.1.3 50-Watt Power Amplifiers ...................................................................................... 3-63
3.7.1.3.1 Transmitter...................................................................................................... 3-63
3.7.1.3.2 Antenna Switch and Harmonic Filter............................................................... 3-64
3.7.1.3.3 Power Control Circuitry ................................................................................... 3-65
3.7.2 UHF Band Power Amplifiers ........................................................................................... 3-68
3.7.2.1 High-Power Amplifier ............................................................................................. 3-68
3.7.2.1.1 Transmitter...................................................................................................... 3-68
3.7.2.1.2 Antenna Switch and Harmonic Filter............................................................... 3-69
3.7.2.1.3 Power Control Circuitry ................................................................................... 3-69
3.7.2.2 40-Watt Power Amplifier ........................................................................................ 3-72
3.7.2.2.1 Transmitter...................................................................................................... 3-72
3.7.2.2.2 Antenna Switch and Harmonic Filter............................................................... 3-73
3.7.2.2.3 Power Control Circuitry ................................................................................... 3-74
3.7.3 800 MHz Band Power Amplifiers .................................................................................... 3-77
3.7.3.1 15- and 35-Watt Amplifiers .................................................................................... 3-77
3.7.3.1.1 Transmitter...................................................................................................... 3-77
3.7.3.1.2 Antenna Switch and Harmonic Filter............................................................... 3-78
3.7.3.1.3 Power Control Circuitry ................................................................................... 3-79
3.7.3.1.4 Temperature Sensing ..................................................................................... 3-81
July 1, 2002
Table of Contents
68P81076C25-C