QAM Marker
Signal Source
rev1.0.5 August 15, 2017
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4)
If the spectrum has a selectable Sweep/FFT mode, the resolution bandwidth may be further reduced
by selecting the FFT mode. The result in Figure 3 is still at a 5 kHz span but at a RBW of 30Hz.
Important to note, the indicated level of 2.31 dBmV is less than measured at the previous RBW
setting. This is an artifact of the measuring process. More accurate results are obtained if the span is
set to a lower value thus increasing the number of data points used to represent the signal on the
screen, refer to Figure 4.
FFT mode is set using the Sweep function. If the sweep mode is set to ‘Auto’ this self-adjusts.
Figure 3
In this figure the accuracy of the marker measurement is affected by
the span setting (5 kHz) being set too wide. Additional resolution is
needed to accurately detect to the true peak. Reduce the Span
setting.
