Cal Amp LMU-2x30 Hardware And Installation Manual page 41

LMU-2x20™ Hardware and Installation Guide
4.2.2.1 Comm Antenna Placement Guidelines
The Comm. Antenna must be located at least 20cm away from vehicle passengers, other
personnel, or bystanders in order to comply with FCC radio frequency exposure limits.
Typically, the Comm antenna used by the LMU for wireless service is a standard 3-dB gain
whip. It mounts with standard mounts (i.e. thru-hole, magnetic mount or peel and stick) and
requires a ground plane to work properly. If possible, it should be located at least 3 feet from
the GPS antenna. Ensure that the cable does not get crushed during installation.
Please note that the antennas provided by CalAmp combine both the GPS and Comm
portions.
4.2.2.2 GPS Antenna Placement Guidelines
In order to maximize the performance of the LMU 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.
14 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
V1.0.10 December 12, 2010
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