Keysight N9927-90001 User’s Guide 655
System Settings
System Configuration
How to select Frequency Reference Source
—Press System 7 > System Configuration > Frequency Ref > Freq Ref
Source then
— Choose from the following:
— Int
Internal frequency reference
— Ext
External frequency reference. Connect the 10 MHz External
Reference to the Ref In/Trig In SMA (f) connector on the FieldFox top
panel. The FieldFox may take up to 10 seconds to lock to a valid
External Reference source
— GPS
Available ONLY with Built-in GPS (Opt. 307). When selected, the
internal GPS is immediately enabled and a search for satellites
begins. When satellites are found, the precision timing signal is NOT
used directly, but is used to correct the absolute frequency of the
internal reference many times per second.
Hold-over mode
When the GPS signal is lost, the last GPS reading is used as a hold-over
correction value for the internal reference. The hold-over correction value is no
longer used, but instead the factory-set correction value is used, when any of
the following occur:
— when GPS is disabled.
— when Reference Source is set to Internal.
— when the FieldFox resumes from Standby mode or shut down.
Frequency Reference Status
When switched to Ext or GPS, one of the following annotations appears in the
lower-left corner of the screen:
— EXT R – External reference is selected.
— GPS R – GPS reference is selected.
— GPS H – Internal Reference is used with last ‘hold-over’ correction reading.
If the FieldFox does NOT find an appropriate Ext or GPS reference signal, then
Ext Ref UNLOCKED is displayed in the lower-left corner of the graticule area.
This can occur when any of the following conditions exist:
— NO reference signal is present.
— A low or very high-level external reference signal is present. For best
results, the signal should be between –5 dBm and +5 dBm.
— The external reference is off-frequency.
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