Discipline Source Phase Measurement
2. Close the Phase Graph and verify that the
Disciplining Status
gets into
Locked
mode.
At this point the test set’s internal “Atomic 10MHz” frequency and “Atomic 1PPS” timing reference signals can be considered accurate and
stable.
The Phase Graph (above) can be used to monitor the short-term stability of the raw GPS clock, which can be used to determine the Discipline
Threshold for a particular site or scenario. Zoom in to the 50ns grid and estimate how disperse the 1PPS samples are (in ns), then use a
larger value as a threshold. A vertical variation of <30ns is OK.
Verifying the Antenna Field of View
Not many of us would be tempted to get on the roof or climb to the top of a tower to perform a 360° visual inspection to identify any potential
satellite signal obstructions. But even if you do, you won’t be able to “see” interference, multi-path or other RF effects.
As all “visible” GNSS satellites move around their orbits, the directional vectors pointing at them form dome above the antenna. Their received
signal qualities change over time, depending on their elevation angles, obstructions, reflections and other factors.
To track this, you need a tool that records the C/No of every satellite as they pass by the antenna’s aperture (field of view), to create a flat
(2D) projection of a 360° color-coded dome-shaped “heat” map representing the field of view of the antenna and the signal quality from every
direction. These azimuthal graphs allow you to identify areas (directions) with degraded signal quality.
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