| 摘要 |
A device for inspecting an individual high frequency signal selected according to frequency from a broad frequency band comprises a voltage controlled oscillator which can be controlled with respect to frequency by a periodic sweep voltage, in particular a linear sawtooth voltage, in such a manner that all signals occurring in the frequency band can be displayed as a spectrum in the picture screen of a cathode ray tube. The device further comprises a frequency marker generator which has a device for generating a frequency mark voltage and a voltage comparator for, given sweep operation and equality between an adjusted frequency marker voltage and a momentary sweep voltage, generating a frequency mark on the picture screen which is adjustable to identify a corresponding fixed frequency after termination of the sweep operation for inspecting an individual frequency-selected signal. The oscillator is a phase controlled oscillator of a synthesizer in whose control loop a transfer switch is provided and operates in such a manner that the sweep voltage switches off in a first position of the switch and the control loop is closed, and the momentary tuning voltage of the control loop is stored. Subsequently, the control loop is opened in a second switch position and the sweep voltage is connected to the control input of the oscillator. In this mode, the stored tuning voltage is compared to the sweep voltage in the voltage comparator of the frequency mark generator for generating the frequency mark. The transfer switch is held in the first switch condition for evaluating the individual signal.
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