a method for calibrating an adjustable frequency generator having a voltage - controlled oscillator which is preceded by a computer via a digital - to - analog converter . the control input of the oscillator is coupled to a calibrating device comprising a series circuit comprising a digital phase detector and a lowpass filter forming a phase - locked loop circuit arrangement . by the computer , a digital - to - analog converter is caused , upon a frequency reference value signal , to deliver a control voltage to the oscillator which corresponds to the output voltage of the lowpass filter prior to the start of the calibrating process . a digital value corresponding to the control voltage is stored in the computer together with a digital reference value corresponding to the given frequency .