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例1 故障现象:接收不到寻呼台的寻呼信号。分析与检修:首先检查射频放大单元,图1为该机低噪声射频放大器原理电路,电路中有三个可调元件,调整可变电容,可使天线的谐振点与接收频率相同,或保证接收信号落到所需的频带内。调整电感T1,可使频带的品质因素Q值提高,调整电感T2,可使射频放大器与混频级达到匹配状态,促使射频放大器的增益达到最佳点。测量晶体管Q1的各极直流工作电压,发现其集
Example 1 Symptom: The paging signal can not be received from the paging station. Analysis and Maintenance: First check the RF amplification unit, Figure 1 is the machine low noise RF amplifier circuit, the circuit has three adjustable components, adjust the variable capacitor, the antenna can be the same resonance frequency and receive, or to ensure that the received signal Fall within the required band. Adjusting the inductance T1 can improve the Q factor of the quality factor of the frequency band and adjust the inductance T2 to match the RF amplifier and the mixing stage so that the gain of the RF amplifier reaches the optimum point. The measurement of each pole of the transistor Q1 operating voltage, it is found