Keysight NFA Series Performance Verification And Calibration Manual page 94

NOTE
Figure 2-17
Test Descriptions
Instrument Noise Figure
Specifications covering the frequency range of 10MHz to <3000 MHz are
referenced to 0 MHz. To calculate the specification for any given
frequency point within this range simply multiply the frequency by the
corresponding dB/MHz value and add the initial dB value.
For example:
Frequency = 1500 MHz
Specification = 1500 * 0.00135 + 5.9dB = <7.925 dB
Typical plots with limit lines for the N8972A
74 Chapter 2