Keysight A Series User Manual page 47

Preparing for Initial Use of Your New FieldFox
Avoid Overpowering the FieldFox
Very often, coaxial cables and antennas build up a static charge, which, if
allowed to discharge by connecting to the FieldFox, may damage the
instrument input circuitry. To avoid such damage, it is recommended to
dissipate any static charges by temporarily attaching a short to the cable
or antenna prior to attaching to the FieldFox.
Keysight N9927-90020 User's Guide 47