Keysight FieldFox B Series User Manual page 713

Noise Figure Mode (Option 356)
Calibration Wizard
User Calibration (User Cal):
Performing a user calibration is recommended only when the
measurement setup includes a preamplifier. The user calibration is
unnecessary for accurate measurements when no preamplifier is used.
In general, a user calibration should be performed whenever a preamplifier is
used in the noise figure measurement. If there is no preamplifier, the user
calibration is not necessary.
Although it will be interpolated if other frequencies are used, when a user
calibration is performed, it should be made at the same frequencies as the
measurement. The user calibration also needs to be performed with the same
resolution bandwidth as is used in the measurement. The user calibration
determines the noise contribution of the preamplifier, so that it can be
removed from the measurement when computing the noise figure of the DUT.
Also, the user calibration establishes the power gain of the
receiver—preamplifier system so that the reported gain of the DUT will be the
gain between input of the DUT (where the noise source is connected during
the measurement) and the calibration plane (which is the point where the
noise source is connected during the user calibration). Therefore, for the best
gain accuracy, the noise source used in the calibration, should be connected
at the same point as the DUT will be during the measurement.
For example of Smart Noise Source User Cal, refer to
page
Keysight N9938-90006 User's Guide
714.
Figure 29-28 on
713