frequency slip频率漂移frequencyn.频繁；频率frequency measurement receiver测频接收机frequency-selective channels频率选择性信道frequency domain reflectometer频域反射仪frequency modulation radio set调频电台frequency-eliminating signal除频讯号Frequency shift monitor system移频监测系统frequency-exchange signaling频率交换信号传输frequency conversion convertor变频变换器frequency optimum transmission最佳发射频率frequency modulation threshold调频门限