Symmetricom XL-GPS - Manual (Page 23)

997-01530-01, Rev. C-25, Jan 2008 13
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3: Installation/Configuration
Installing the GPS Antenna
For XL-GPS units include a standard GPS receiver, antenna, and antenna cable. Install as described
below.
Selecting a GPS Antenna Site Outdoors
Select a site that...
• Is the highest point available
• Offers a full 360 ° view horizontally, to within 10° vertically of the horizon
• Is higher than neighboring buildings/obstructions
• Is protected from strong radio frequency (RF) and microwave transmissions
• Is set away from RF-reflective surfaces that cause multipath interference
• Is set 3 ft. (1 m) away from other GPS antennas
Avoid...
• Mounting the antenna between tall buildings or next to walls and equipment
• Cable runs from the antenna to the receiver that exceed the specified length
• Patching multiple cables together to make a single cable run
• Running the cable through bulkheads and along side high-energy cables
• Crimping or damaging the cable
For test situations, a GPS antenna can be placed in a window. Equatorial-facing (e.g., south-facing for
users in the northern hemisphere) windows provide the best visibility of satellites. However, if the
equatorial-facing window has large obstructions such as trees or buildings, a window facing another
direction with fewer obstructions may be better. Metal window shades and special metallic window
coatings may block GPS signals entirely.
Blocked signals and multipath cancellation significantly increase GPS acquisition time. Multipath
cancellation is caused by reflected signals that reach the antenna out of phase with the direct signal.
Multipath cancellation and blocked signals are typically caused by vertical reflective objects positioned to
the side and above the antenna. To solve these problems, mast mount the antenna at least 1 meter
away from and above the reflecting surface.
Mounting the GPS Antenna
Mount the GPS antenna on an antenna mast (recommended) or on the peak of a building. The GPS
antenna kit includes special mounting brackets. For the mast, use 2-inch (5.08-cm) diameter water pipe