I am using the spectrum analyser to measure a digital signal.
I have set it to:
It seems that the VBW has an effect on the digital level value.
Are you sure that the VBW must be set at 300Hz?
I have done this before, and I have not included this value.
-->The resolution bandwidth is not important when measuring digital signal levels.
The only thing you must do is apply a correction factor according to the resolution bandwidth selected.
This factor is calculated by using the following formula:
Real level = analyser reading + 10log (7800000/RBW)
Therefore, the correction factor is:
However, in order to be able to see the intermodulation products of the digital signal on the analyser screen, the maximum resolution bandwidth must not exceed 300 KHz.
The video filter is a function of the spectrum analyser being used.
In practice, the measurement can differ depending on the video filter that is being used:
The best settings for the video filter are:
The sweep time SWP is a parameter that is selected automatically by the spectrum analyser depending on the previous settings.
It never affects the measurement results.