
210
FieldFox User’s Guide
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:
o
when GPS is disabled.
o
when Reference Source is set to Internal.
o
when the FieldFox resumes from Stand By 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.
To learn the expected measurement accuracy when connected to a frequency
reference source, see the FieldFox specifications on page 232.
Reference OUT
The internal 10 MHz frequency reference is available from the
Ref/Trig
output
connector on the right-side panel. Use this signal as a common frequency
reference when making measurements using external equipment. See this
connector on page 17.
Voltage Source (Opt. 309)
An internal DC source, available with Opt. 309, may be used to provide power for
external devices. The maximum power available is 8 watts.
The voltage is output through an SMB(m) output connector located on the left-
side panel. See the connector on page 17.
An optional SMB (f) to BNC (m) bias-tee power cable is available with Agilent
part number: N9910X-713.
The following status line is provided near the top of the FieldFox screen.
Voltage Source Status Line
1.
Voltage source state: ON, OFF, TRIPPED.