Symmetricom GPS Antenna, Руководство по установке

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GPS Antenna Sets
Installation of the
GPS Antenna
4. Installation of the GPS Antenna
This chapter provides procedures to be performed when installing a GPS antenna
4.1. Selection of a Suitable Location
GPS signals don’t penetrate walls, roofs, solid metal structures or dense foliage. Tracking
more satellites improves the GPS system performance. Typically at least 4 satellites are
needed for start-up and at least 1 satellite continuously. For best results select an outdoor
location providing as much unobstructed view to the sky as possible. Obstructions not
rising more than 10° above the horizon can be ignored. Since the moving GPS satellites
don’t cross the polar regions view towards the earth’s equator is preferable. Hence, in the
northern hemisphere (Europe, North America, most of Asia) the sector E-S-W must be
considered while in the southern hemisphere (Australia, South America) it’s W-N-E.
Rooftop mounting is ideal. Wall mounting may be acceptable, particulary at higher levels.
The figure shows different location options and their pros and cons are discussed below.
Position 1: Few obstructions towards the important region. Potential to track up to 8 satellites.
Best results.
Position 2: Some obstructions. Potential to track 4 to 6 satellites. Reasonable results.
Position 3: Many obstructions. Potential to track 1 to 4 satellites. Depending on time of day
(satellite constellation) start-up may be delayed significantly. Marginal results.
Position 4: GPS satellite signal blocked almost completely. Potential to track up to 2 satellites. No
performance.
Lightning protection may be important. If the desired location is not within the area
protected against direct strikes the building’s protection system must be modified
accordingly. Local building codes may apply.
001023AD – July 2003
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