1019
Marker Function
The sequence of steps in the measurement is as follows:
• Any sweep in progress is aborted.
• If in Zero Span, the Center Frequency is used as the frequency at which to take the reading, since in
Zero Span, all markers are by definition at the Center Frequency
• If not in Zero Span:
— If the selected marker is Off, it is first turned on in the center of the screen and a peak search
performed.
— If the selected marker is on, but offscreen, it is first moved to the center of the screen and a peak
search performed.
— A frequency “zoom” function is performed to determine the frequency of the selected marker to
the required precision. If you are operating with too large a value of (span/sweep points) then the
Measure at Marker window will not display, but instead an advisory message, “Span per point too
large, narrow span or increase RBW or number of points”.This means you have chosen a
combination of RBW, span and sweep points that makes each trace point much wider than the
RBW, so that the trace point in which the signal appears is an inadequately precise measure of its
frequency—for example, with a 30 MHz to 1000 MHz span, 601 trace points and 120 kHz RBW,
each trace point is 13 times as wide as the RBW. In this case, a SCPI query of the results will yield
–999 dBm for each detector.
— If the zoom is successful, the test set goes to zero span at this frequency
• Each detector is then read in successive single-point zero span sweeps, using a sweep time equal to
the specified dwell time. The value displayed by Measure at Marker represents the maximum value
output by the detector during the dwell time Autocoupled bandwidth and average type settings are
used for each detector unless the BW & Avg Type key is set to As Set, in which case the current
bandwidth and average type settings are used.
• Each result is then displayed in the measure at marker window as it becomes available.
• The test set returns to its pre-Measure at Marker span and settings after executing a Measure at
Marker function, including Bandwidth, Avg Type, and EMC Std - regardless of the setting of BW &
Avg Type
• Finally, if the sweep had to be aborted, the aborted sweep is restarted.
While the function is executing, all the fields except Freq show --- for their values until the measurement
is complete for that detector. As each detector is read, an informational message is displayed in the
status line, for example,
Measuring with detector 1 (Peak) with RBW=120 kHz
After the last detector, the status line is cleared.
Meas at Marker Window
This key opens a menu which controls the Measure at Marker window.
Key Path Marker Function, Measure at Marker