RIGOL DSA875 - Manual (Page 139)

Chapter 2 Front Panel Operation RIGOL
User’s Guide for DSA800 Series 2-87
Marker Fctn
Special marker functions including Noise Mkr, N dB BW and Freq Count.
Select Mkr
Select the marker to be used for the specified measurement function and the
default is marker 1.
Noise Mkr
Execute the Noise marker function for the selected marker and read the noise
power spectral density.
Key Points:
 If the current marker is “Off” in the Marker menu, pressing Noise Mkr will
first set it to Normal type automatically; then measure the average noise level
at the marked point and normalize this value to 1 Hz bandwidth. During this
process, certain compensation is always made on the basis of the detection
and trace types. The measurement will be more precise if RMS Avg or Sample
detection type is used.
 This function can be used for measuring the C/N ratio.
N dB BW
Enable the N dB BW measurement or set the value of N dB.
The N dB BW denotes the frequency difference between two points that are
located on both sides of the current marker and with N dB fall (N<0) or rise (N>0)
in amplitude as shown in the figure on the next page.