310                                                                                                                     Keysight N9927-90001 User’s Guide
Interference Analyzer (SA Mode) – Option 236
Spectrogram and Waterfall Displays
— At the current sweep speed, the difference in time between these two 
markers appears at the upper-right corner of the view as Delta Time: 
hh:mm:ss Sec.
— An invalid number (very large positive or negative) appears when a trace 
record is not available at either marker. 00:00:00 Sec appears when both 
markers are not available.
Common Settings for Waterfall and Spectrogram
Set Red and Blue Limits
The colors displayed on the Waterfall and Spectrogram represent the various 
measured power levels:
— Red = Highest power levels
— Blue = Lowest power levels
Adjust the Red and Blue limits to the power levels that you expect to measure.
The Blue limit must always be less than the Red limit. 
For SA Mode:
—Press Meas Setup 4.
—Then Spectrogram Settings
 or Waterfall Settings
— Then choose from the following: 
— Red Limit
 Using the   arrows, rotary knob, or keypad, select the 
HIGHEST power level that you expect to measure. This power level, 
and those measured higher than this level, appear Red.
— Blue Limit
 Using the   arrows, rotary knob, or keypad, select the 
LOWEST power levels that you expect to measure. This power level, 
and those measured lower than this level, appear Blue. 
How to Restart the Spectrogram/Waterfall
Press Sweep 3 then Restart
Waterfall settings only apply to the SA option.
The full Red-to-Blue color spectrum is visible only with Indoor display 
colors. Learn more in “Display Colors” on page 513.