Agilent Technologies N9913A User Manual page 144

During External Zeroing, the power source MUST be turned OFF or the power
sensor disconnected from the power source (device under test). Power is OFF
when power sensor measurements are below –60 dBm. When power higher than
this is detected at the sensor, a warning message is shown on the FieldFox and
External Zeroing will not proceed.
NOTE External Zeroing is NOT allowed on the U2020 X-series Power Sensors.
How to perform External Zeroing
 Press Cal 5 .
 Then
External Zero.
While either Internal or External Zeroing is being performed, "Zeroing..." is
shown on the FieldFox screen. While this message is present, do NOT make any
changes to the FieldFox.
In addition, once External Zeroing has started, the power source must be OFF for
the entire time that the Zeroing message is present. Otherwise, the calibration
will be compromised but NO warning is shown.
Frequency
A table of correction factors versus frequency is stored within Agilent Power
Sensors. The frequency of the power to be measured is entered in the FieldFox so
that the appropriate correction factor can be used.
The Source Control feature (see following section) will determine the frequency
range of the power measurement.
How to enter Frequency of the Power Measurement
 Press Freq/Dist or Meas Setup 4 .
 Then Frequency.
 Then type a value using the numeric keypad. The default frequency is 50 MHz.
 Then press a multiplier key. Learn about multiplier abbreviations on page 19.
The current frequency is shown on the FieldFox screen.
Source Control
This feature may require an option on some FieldFox models.
With the FieldFox internal source enabled, these settings allow you to make
simple, absolute power measurements. The source and the power sensor can be
physically separated by a long distance when using a long USB cable.
Set the internal source frequency by setting the frequency of the power
measurement. Learn how in the previous section.
Power Meter measurements are limited by the combined frequency ranges of the
internal source when enabled and the frequency range of the power sensor. For
example, assume the frequency range of your sensor is 9 kHz to 18 GHz and the
frequency range of the FieldFox is 2 MHz to 6 GHz.
 With the Source ON, measurements are limited to 2 MHz to 6 GHz.
 With the Source OFF, measurements are allowed from 9 kHz to 18 GHz.
144 FieldFox User's Guide