GPS Antenna Placement Guidelines
In order to maximize the performance of the TTU the GPS antenna should have a clear view of the
sky. When installing the GPS antenna on a vehicle, make sure that there are no obstructions close to
the antenna that might block the view
360° to the horizon. Things like air horns, lights, vents, etc…
should not block the antenna beyond 5° above the horizon. The best location is usually near the center
of the roof; however it is also desirable to locate the cellular antenna as far from the GPS antenna as is
practical.
Examples of good and poor GPS antenna placements
The received signal levels at the GPS antenna from the satellites are very low in power (approximately
-136 dBm), so any blockage of the antenna can affect the quality of the location computed by the
receiver. Kinks or tight knots in the antenna cable can also prevent the GPS receiver from operating
properly. When laying out the antenna cable, care should be taken so that the cable is not subjected to
crushing or strain.
Placement of Combination and Internal Antennas
When dealing with combination antennas, it is more important to considered GPS performance over
Comm performance. GPS signal strengths are much lower than those typically seen by cellular
networks supported by the TTU. In order to maximize the performance the TTU should have a clear
view of the sky as possible. When installing the GPS antenna in a vehicle, make sure that there are as
few obstructions as possible close to the TTU that might block the view 360° to the horizon. As with
stand-alone GPS antennas, nothing should not block the combination antenna beyond 5° above the