Hytera MD78X Service Manual page 8

Service Manual
12.1.9 Output Power Control ....................................................................................................... 320
12.1.10 Thermal and Over-voltage Protections .......................................................................... 320
12.1.11 Pressure Pad Switch ...................................................................................................... 320
12.2 Receiver Circuit .......................................................................................................................... 320
12.2.1 Receiver Front-end........................................................................................................... 321
12.2.2 Receiver Back-end ........................................................................................................... 322
12.3 Frequency Generation Unit (FGU) ............................................................................................. 322
12.3.1 PLL Synthesizer ............................................................................................................... 322
12.3.2 Reference Oscillator ......................................................................................................... 323
12.3.3 PLL IC ............................................................................................................................... 323
12.3.4 VCO .................................................................................................................................. 324
12.4 PCB View .................................................................................................................................... 325
12.5 Block Diagram ............................................................................................................................ 329
12.6 Schematic Diagram .................................................................................................................... 332
12.7 Parts List ..................................................................................................................................... 346
12.8 Troubleshooting Flow Chart ....................................................................................................... 385
13. UHF3 (350-400MHz 45W) Information .......................................................................................... 391
13.1 Transmitter Circuit ...................................................................................................................... 391
13.1.1 Power Amplifier ................................................................................................................ 391
13.1.2 TX Buffer Amplifier ........................................................................................................... 391
13.1.3 Pre-driver Power Amplifier ............................................................................................... 392
13.1.4 Driver Power Amplifier ...................................................................................................... 392
13.1.5 Final Power Amplifier ....................................................................................................... 392
13.1.6 Antenna Switch ................................................................................................................. 392
13.1.7 Low-pass Filter ................................................................................................................. 392
13.1.8 Directional Coupler ........................................................................................................... 393
13.1.9 Output Power Control ....................................................................................................... 393
13.1.10 Thermal and Over-voltage Protections .......................................................................... 393
13.1.11 Pressure Pad Switch ...................................................................................................... 393
13.2 Receiver Circuit .......................................................................................................................... 393
13.2.1 Receiver Front-end........................................................................................................... 394
13.2.2 Receiver Back-end ........................................................................................................... 395
13.3 Frequency Generation Unit (FGU) ............................................................................................. 395
13.3.1 PLL Synthesizer ............................................................................................................... 395
13.3.2 Reference Oscillator ......................................................................................................... 396
13.3.3 PLL IC ............................................................................................................................... 396
13.3.4 VCO .................................................................................................................................. 397
13.4 PCB View .................................................................................................................................... 398
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