228                                                                                                                     Keysight N9927-90001 User’s Guide
RTSA (Real-Time Spectrum Analyzer) Mode—Option 350 (CPU2 Only)
RTSA Mode Settings
—Center and Freq Span frequencies. This is the most common method 
of entering frequency range. Enter the frequency of interest. The 
Center frequency is at the exact center of the X-axis. The Frequency 
Span places half of the frequency range on either side of center. 
When the Center and Frequency Span values are entered, then the 
X-axis annotation on the screen shows the Center and Span 
frequencies. 
—Start
 and Stop frequencies. Start is the beginning of the X-axis and 
Stop is the end of the X-axis. When the Start and Stop frequencies 
are entered, then the X-axis annotation on the screen shows the Start 
and Stop frequencies. 
— Optionally, press More
 then:
——CF Step
 then type a step size value using the numeric keypad, 
then select a multiplier key.
——Freq Annotation
 and one of the following:
——Full Span
 the frequency span changes to 10 MHz.
— Follow each of these, when prompted, by entering a value using the 
numeric keypad, the   arrows, or the rotary knob.
— When using the   arrows, press Enter
. The increment setting of the 
arrows is based on the current span. This can be changed in RTSA Mode.
— After using the keypad, select a multiplier key. Learn more in “Multiplier 
Abbreviations” on page 43.
Scale and Units
Adjust the Y-axis scale to see the relevant portions of the data trace. 
The Y-axis is divided into 10 graticules. A acquisition is shown on the screen as 
a solid horizontal bar that can be placed at any graticule.
RTSA always uses logarithmic scale. The Y-axis reference line represents the 
specified absolute acquisition (dBm). Y-axis graticules show dB below or above 
the reference line.
When RF Attenuation set to Auto, the RF Attenuation is coupled to acquisition. 
AutoSelect (Default) – The FieldFox selects a frequency annotation 
setting (CenterSpan or StartStop).
CenterSpan -The center frequency and span are displayed.
StartStop - The start and stop frequencies of the frequency span are 
displayed.