80                                                                                       Keysight FieldFox Handheld Analyzers Service Guide
Theory of Operation
Operation in Modes
5-
For a given mode, the analyzer “remembers” the most recent state of the 
current mode when you change to another mode.
For most screens under System 7 key, the current measurement mode 
continues to operate while the screen is displayed. For instance, while the 
battery information screen is displayed, the measurement mode remains 
active.
There are two exceptions to this:
— the “Options (Licensing)” screen
—“Error Log” screen
When either of these screens is displayed, the firmware is in a special monitor 
mode and measurements are suspended.
CAT, NA, and VVM Modes
CAT, NA, and VVM modes have some similar capabilities but are still separate 
operating modes.
Measurement similarities:
— Return Loss = S11 magnitude
— Insertion Loss = S21 magnitude
Unlike S11 and S21, the values displayed below zero for Return Loss and 
Insertion Loss are not negative.
There is user control of output power level, which is high, low or manual setting 
on the RF Out Atten, 35 dB in or out.
SA and CPM Mode
SA Mode measures signals at the SA RF IN connector. 
SA Mode measurements require NO calibration.
The signal path for SA mode is the same as the input path for two port CAT/NA 
modes.
ERTA Source Source 
Enable
OFF ON
Source Mode
(CW)
Normalize 
(OFF ON)
Source Power Source CW 
Freq
Option 209
& 233
Option 209
& 233
Option 209
& 233
Option 209
& 233
Option 209
& 233
Modes CAT/TDR NA SA VVM Power Meter
(USB Sensor)
Power Meter
(Built In)