Hytera MD78X Service Manual page 5

Contents
8. UHF1 (400-470MHz 25W) Information .............................................................................................. 29
8.1 Transmitter Circuit .......................................................................................................................... 29
8.1.1 Power Amplifier .................................................................................................................... 29
8.1.2 TX Buffer Amplifier................................................................................................................ 29
8.1.3 Pre-driver Power Amplifier ................................................................................................... 30
8.1.4 Driver Power Amplifier .......................................................................................................... 30
8.1.5 Final Power Amplifier............................................................................................................ 30
8.1.6 Antenna Switch ..................................................................................................................... 30
8.1.7 Low-pass Filter ..................................................................................................................... 30
8.1.8 Directional Coupler ............................................................................................................... 30
8.1.9 Output Power Control ........................................................................................................... 31
8.1.10 Thermal and Over-voltage Protections .............................................................................. 31
8.1.11 Pressure Pad Switch .......................................................................................................... 31
8.2 Receiver Circuit .............................................................................................................................. 31
8.2.1 Receiver Front-end ............................................................................................................... 32
8.2.2 Receiver Back-end ............................................................................................................... 33
8.3 Frequency Generation Unit (FGU) ................................................................................................. 33
8.3.1 PLL Synthesizer ................................................................................................................... 33
8.3.2 Reference Oscillator ............................................................................................................. 34
8.3.3 PLL IC ................................................................................................................................... 34
8.3.4 VCO ...................................................................................................................................... 34
8.4 PCB View ........................................................................................................................................ 36
8.5 Block Diagram ................................................................................................................................ 40
8.6 Schematic Diagram ........................................................................................................................ 43
8.7 Parts List ......................................................................................................................................... 57
8.8 Troubleshooting Flow Chart ........................................................................................................... 95
9. UHF1 (400-470MHz 45W) Information ............................................................................................ 101
9.1 Transmitter Circuit ........................................................................................................................ 101
9.1.1 Power Amplifier .................................................................................................................. 101
9.1.2 TX Buffer Amplifier.............................................................................................................. 101
9.1.3 Pre-driver Power Amplifier ................................................................................................. 102
9.1.4 Driver Power Amplifier ........................................................................................................ 102
9.1.5 Final Power Amplifier.......................................................................................................... 102
9.1.6 Antenna Switch ................................................................................................................... 102
9.1.7 Low-pass Filter ................................................................................................................... 102
9.1.8 Directional Coupler ............................................................................................................. 103
9.1.9 Output Power Control ......................................................................................................... 103
9.1.10 Thermal and Over-voltage Protections ............................................................................ 103
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Service Manual