Measuring spectral features using a cursor and a marker

An improved marker and cursor system for spectral waveform measurement permits the operator to link or unlink a cursor and a marker, allowing them to be used separately or in coordination to make bandwidth measurements. A second reference marker permits measurement of the frequency and amplitude differneces between it and the marker at the same time that the marker is being used control the linked cursor. The cursor can be fixed or linked in a constant positive or negative delta-amplitude relationship to the marker. The points on the cursor where the cursor and spectral waveform intersect are intensified for identification and a readout is provided of the difference in frequency values between these points. Measurements continue even during unstable conditions of the instrument or spectral waveform and fluctuations show up as only minor movements of the intensified points along the cursor. If there is no intersection of the cursor and spectral waveform in one direction, the absolute frequency value of the other intersection is displayed instead of a delta-frequency value.