Symmetricom TimeSource 3600, Manual

Page: 45 / 254

2
Engineering & Ordering
45
2
4
5
3
S S S S S S S S S S S S S S S S S S S S S S S S S S S S S
Window and Wall Antenna Location Guidelines
When selecting a window or wall in which to install the antenna,
select the window or wall which has the maximum unobstructed
view of the sky. Do not select a window or wall which has the view
of the sky obstructed by trees, buildings, or towers. The smaller
the field of view, the fewer the number of satellites that can be
used in the timing solution for GPS derived time. The consequence
of this is that the timing generator may experience holdover more
often and may eventually go into alarm.
Due to the geometry of the GPS satellite orbits, more satellites are
visible in the direction of the equator than the poles. If possible,
select a window or wall which has a clear view toward the equator
(toward the south in the northern hemisphere, or toward the north
in the southern hemisphere). This guideline is less applicable in
latitudes nearer the equator and more important nearer the poles.
Certain parts of the sky are blocked from view. These obstructions
usually exist from the horizon line and up, for example, a building
or mountain. The processor inside the GPS receiver possesses
every piece of the sky, whether it is blocked or not. If unproductive
parts of the sky are masked from the processor’s view, the
processing time is reduced, and the timing solution can be
achieved more quickly.
Note:
A band of the sky from the horizon up to a point where a
view of the sky begins is called a mask angle. The mask angle typi-
cally should not exceed 10 degrees (if the mask angle is set too
high, too little of the sky is available to the receiver). Determine the
mask angle for the selected antenna location (Figure 11) and make
a note of it. The mask angle, in degrees, will be entered during the
initial setup.