Marker Type (Markers)

The marker type is set by the first dropdown box in the Visible group in the Markers > Position tab. There are three types of markers which are listed below:

Normal - a normal marker is used to inspect the current value of a trace and is confined to the current trace line.
Delta - the value of a Delta marker is calculated as an offset from the reference marker. The reference marker is not confined to the same trace as the delta marker.
Fixed - a fixed marker is not confined to the current trace but can be placed at any X, Y, Z, and Trace Time position.

The Normal and Delta markers for a given trace are confined to be within the same trace (although reference markers are not). On a spectrogram or heatmap trace this implies the Normal and Delta markers all share the same scan line, which can be selected by dragging the line up and down, or by modifying the Trace Select parameter.

Normal marker type

Normal markers are placed at a certain x-axis value and are used to read out the Y-axis value at that X-axis location.

Markers can have a Z-axis position. This position is set to 0 unless the trace contains Z-axis information (see About OFDM Markers for more information).

Markers placed on a spectrogram also have a Trace Time position. This trace time position is the same for all normal and delta markers and is determined by the Trace Select parameter in the Markers > Spectrogram tab. See Spectrogram Markers for more information.

Delta marker type

The Delta marker is like a normal marker in all respects except that the value shown in marker readouts is calculated as an offset (or a ratio when the trace format is Lin Mag or Log Mag (lin)) from the reference marker for the delta marker. The reference marker can be on the same trace as the delta marker, or it can be on a different trace.

If the reference marker is on a different trace from the delta marker and the units are mixed between traces (e.g., V and dBm deciBels referenced to a milliWatt: dB relative to 1 milliwatt dissipated in the nominal input impedance of the analyzer, or dBm and deg), the results will not be meaningful.

The delta marker is shown on the trace as a diamond symbol like normal markers. The delta marker's annotation is of the form XDTR where X is the number of the delta marker, T is the trace where the reference marker is located (if the reference marker is on a different trace), and R is the reference marker. The same format is used in the Markers Window.

A delta marker can be quickly created by adding a marker to a trace, moving the marker to the reference location and then right-clicking the trace grid and choosing Zero Delta.

Fixed marker type

The Fixed marker is unlike Normal and Delta markers since it is not confined to the current trace but is free to move anywhere in the trace area. For spectrograms, the fixed marker is also able to be located on any trace in the spectrogram's trace buffer.

This is useful when measuring an offset between two different measurement updates. To do this, place a normal marker on the trace and click Zero Delta. This will create a fixed marker in the same location as the normal marker and will change the normal marker to a delta marker with the fixed marker as the reference. Then let the measurement run and move the delta marker to calculate the offset from the fixed marker.

The fixed marker is shown on the trace as an 'X' symbol. The point selected by the fixed marker is the center of the 'X'.