What is the difference between the spectral analysis being performed under Spectral Analyzer and Real-Time Spectrum Analyser?
The Spectral Analysis graph allows you to see how the levels of the frequency span vary up and down as the signals change but there is no way to get a feel for how long any given signal was present.
Real-Time Spectrum Analysis has Persistent Display mode which gives a different level of visibility to the signal being viewed. It presents the signal based on the time that a given signal was active in frequency and power. This is done using different colors to represent the amount of power that signal exhibited. Colors range from dark blue to represent 0% then ranging to light blue, light green, green, yellow and up to red, with red representing 100% power. So instead of just seeing a line go up and down, the user sees a block of colors reflecting the amount of time the signals were present at their varying power levels. By viewing the different colors present, the user can tell how long, or "persistent" , the signal was at the various frequencies.