Vector Network Analyzer Measurement Guide : VNA Display Overview : Marker and Limit Capabilities
 
Marker and Limit Capabilities
Marker Description
A marker is a tool for extracting results from traces (or from trace memory). 12 independent markers can be assigned to any one trace (or to all traces). User‑defined attributes for a marker include: Marker Type (reference or delta) and Readout Style.
In the marker menu, the markers are selected by using the Marker soft key. Select an active marker with the rotary knob, arrow keys, or key pad (by pressing the marker number). If you select a marker that is Off, then this action will automatically turn On the marker and assign it to the current active trace as a reference marker. After a marker is selected from the Select Marker List Box, an input parameter window (located in the upper left‑hand corner of the display and using red font text) displays the current location (frequency, time, or distance) of the marker. The input parameter accepts keypad, rotary knob, or arrow key input to move the marker to the desired location on the active trace.
Selecting the Readout Style for Each Marker
In the Marker menu, press Readout Style to specify a readout style that differs from the current graph type, or select “As Graph Type(GT)” to have the marker use the same readout style as the current graph. For example, if active trace graph type is Log Magnitude, then default Readout Style is Log Magnitude. You can use Readout Style, however, to select any of the available styles for your preferences. In addition to “As Graph Type(GT)”, these Readout Style selections include: Log Mag, Log Mag and Phase, Phase, Real and Imaginary, SWR, Impedance, Admittance, Normalized Impedance, Normalized Admittance, Polar Impedance, Group Delay, Log Mag/2, Linear Magnitude, and Linear Magnitude and Phase.
Displaying Markers on the Screen
By default, the active marker is displayed on the active trace. Location can be manipulated by keypad, rotary knob, or arrow key input. Location can also be manipulated by a finger tap on a touch screen. Additional flexibility is offered either to display the marker readout on the Trace, Screen, or Table, or to turn Off the display of marker readout information (displaying only the marker symbol on the trace). Press the Readout Format soft key to make your choice (refer to Readout Format Menu).
1. Press Trace to select marker readout on the trace, which overlays the active marker readout directly on the active trace.
2. Press Screen to select marker readout on the screen, which overlays the active marker readout at the upper‑left corner of the display screen (sweep window).
3. Press Table to select marker readout in the table, which shrinks the display enough to list marker readouts at the bottom of the display screen. This selection allows easy viewing of not only the active marker, but of all markers. Note that the color of the marker readout in the table corresponds to the color of the trace to which it is assigned. If a marker is set to be on all traces, then the table listing shows that marker readout for the active trace only.
If multiple markers are displayed in the table, and if the marker data is displayed with overlapping text, then the readout format can be set to Small with the Marker Text Size soft key in the Readout Format menu. To see an example of overlapping test that is made more clear with this feature, refer to Figure: Cable with Failing Return Loss (Marker Text Size = Regular) and Figure: Cable with Failing Return Loss (Marker Text Size = Small).
Setting Up Delta Markers
If the intent is to conduct a delta measurement, then two markers are necessary: one for the reference and one for the delta. As an example:
1. Turn on Marker 1 (the Ref marker) and assign it to a trace.
2. Turn on Marker 2 and toggle the Marker Type from Ref to Delta.
3. Assign Marker 2 to Marker 1 by specifying the Avail Ref Mkr to Marker 1.
The third step allows you to specify marker delta on one trace, and it also allows you to specify marker delta between two traces.
Note that the Select Marker list box includes the current location, readout style, and delta status (if they exist). Otherwise, it indicates Off.
Setting Up Limits
The following description is a brief reminder. For a more detailed description of limits, refer to section Limit Menus.
Each trace with a rectangular graph (not Smith Chart or Polar) can be assigned both an upper limit and a lower limit. The limits can apply to the entire trace or to a portion of the trace, as desired. To set up a simple limit, select the limit menu (refer to Limit Menu) by pressing the Shift key and the Limit (6) key, and then select the active trace. Choose Upper or Lower by pressing the Limit soft key. Next, press the Limit State soft key to toggle the limit line from Off to On (Notice how the limit line is now displayed on the active trace). Adjust limit values by using the Limit Edit submenu, which allows you to adjust the entire limit line or each point of the limit line. Limit Alarm and Pass Fail Message can be separately assigned for each limit line or for each limit point.
Markers on a Touch Screen
The touch screen marker placement feature is active only when the Marker menu is displayed. If the Marker menu is not displayed, then the touch screen behavior differs (refer to Touch Screen Trace Features).
Moving a Marker
In both VNA Measurements view and Field Measurements view on touch screen instruments, whether Trace Format is Single, Dual, Tri, or Quad (VNA view) or whether Display Type is Single, Dual or Overlay (Field view), you can move an active marker on the active trace by touching anywhere on the sweep window of the active trace, but only when the Marker menu is displayed.
If you touch an inactive trace (when more than one trace window is displayed), your first touch selects the trace as the active trace. Lift your finger and touch again to move the active marker.
You can touch and hold to place the active marker, or you can slide your finger to drag the marker along a trace. Your touch point represents a location on the x‑axis, and this touch point may be anywhere on the y‑axis, or even within the Marker Table when it is displayed (On).
Note 
Note that when Marker Table is displayed with a zero span (start frequency = stop frequency), the marker frequency is labeled with the trace point number in parenthesis. For example: MK1 500 kHz(101) –4.99 dB