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Appendix D Performance Tests
Before You Start
D-4 Operating and Programming Guide
Before You Start
The time required to acquire lock as described in the following section
can vary significantly depending on your local conditions. In general, it
is strongly recommended that your antenna and cables be set up in
accordance with the information provided in the documents listed
below prior to performing any of the tests that follow, or the results
cannot be assumed to be valid.
Documents providing GPS Antenna System information are:
• Designing Your GPS Antenna System Configuration Guide
configuration guide, which discusses the components of an
GPS timing receiver system and how to custom design the
configuration of your antenna system. Contact your local Sales
office for a copy of this guide.
• Information Notes that provide installation procedures for the
applicable GPS antenna and accessories that you purchase.
Acquiring lock does not mean that the unit is fully operational and
meeting specifications. It just means that the GPS Receiver has
detected enough satellites to start its survey mode to determine its
precise location. An Internal measurement FFOM (Frequency Figure
of Merit) becomes 0 when the internal loops reach their proper time
constants, indicating that the output frequency and 1 PPS signals are
now fully operational and meeting their specifications. Under the
worst conditions, the GPS Receiver may take 24 to 72 hours to achieve
FFOM = 0. FFOM can be monitored in the Reference Outputs
quadrant of the Receiver Status screen (see the sample status screen,
Figure 3-1, in Chapter 3, “Visual User Interface,” of this guide if
needed). Also, using :PTIMe:TCODe? query command will provide the
FFOM value.