Roof Antenna Location And Cabling Guidelines - Symmetricom TimeSource 3600 User Manual

Roof Antenna Location and Cabling Guidelines

Warning: To avoid serious personal injury or death, do not select an
antenna location that could be an electrical or physical hazard to work
persons or equipment. Avoid proximity to all high-voltage sources.
Mount in an easily maintainable location.
The ideal roof antenna location provides a clear, unobstructed view of the sky from
the zenith to the horizon line, and 360 degrees around the horizon.
A compromise often must be made between location and satellite field of view. With
a smaller field of view, the TimeSource 3600 can use fewer satellites in the solution
for GPS derived time. The TimeSource 3600 will operate with an average of one
satellite in view for 40 percent of the time in a day.
Signals closer to the horizon are often subject to multipath effects, which degrade
the timing solution. The TimeSource 3600 can be set to ignore, or mask, all signals
from the horizon up to a chosen angle of elevation (mask angle). (See Figure 2-1..)
Antenna position
Antenna
field of view
10°
Mask angle*
Horizon
Equator
* An angle of 10° masks objects up to about 1 m above the
horizon at 6 m from the antenna (illustration at right.)
Figure 2-1. Antenna Field of View
Due to the geometry of the GPS satellite orbits, more satellites are visible in the
direction of the equator than the poles. If possible, place the antenna so that the
antenna has a clear view toward the equator (toward the south in the northern
hemisphere, or toward the north in the southern hemisphere). Up to 60 degrees of
arc, centered at the pole, may be blocked with little effect in the temperate latitudes.
This note is less applicable in latitudes nearer the equator.
097-72060-01 Revision J – June, 2007
Chapter 2 Engineering & Ordering
Antenna Guidelines
Obstructions
toward the pole
if possible
10°
Mask angle*
Pole
10°
1 m
6 m
TimeSource 3600 User's Guide 43