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Question 173

What is the effect of aliasing on a digital oscilloscope when displaying a waveform?

  1. A false, jittery low-frequency version of the waveform is displayedCorrect answer
  2. The waveform DC offset will be inaccurate
  3. Calibration of the vertical scale is no longer valid
  4. Excessive blanking occurs, which prevents display of the waveform

Explanation

Signal components above half the sampling rate are folded down and reconstructed at the wrong frequency, so the screen shows a slow waveform that is not present in the signal, unsteady because its samples are not phase-coherent with it. Vertical calibration, DC offset and blanking are unaffected.

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Question 173: What is the effect of aliasing on a digital oscilloscope… · FCC Amateur Extra Class (Element 4) · Questena