USER’S GUIDE SF-2110, User Manual

Page: 42 / 95

SF-2110 User Guide – Rev. A
9
Avoid placing the antenna where more than 90º
azimuth of the sky is obstructed. When more than
90º of azimuth is shaded, it is often still possible
for the reciever to navigate, however, poor
satellite geometry (due to satellite shading) will
provide poor positioning results. Even 10º of
shading can have a negative effect on
performance, though this generally is not the
case.
9
Avoid placing the antenna on or near metal or
other electrically reflective surfaces.
9
Do not paint the antenna enclosure with a
metallic-based paint.
9
Avoid placing the antenna near electrical motors
(elevator, air conditioner, compressor, etc.)
9
Do not place the antenna too close to other active
antennas. The wavelength of L1 is 0.19m. The
minimum acceptable separation between
antennas is 1m (39 in), which provides 6dB of
isolation. For 10dB of isolation, separate the GPS
antennas by 2.5m (8ft), and for 13dB of isolation
(recommended) separate the antennas by
5m (16ft).
9
Active antennas (those with LNA’s or amplifiers)
create an electrical field around the antenna.
These radiated emissions can interfere with other
nearby antennas. Multiple GPS antennas in close
proximity to each other can create multipath and
oscillations between the antennas. These add to
position error or the inability to process the
satellite signals.
9
Most antenna’s have better gain when the satellite
is high in elevation. Expect tracking performance
to fade as the satellite lowers in elevation. It is not
unusual to see 10dB difference in antenna gain
3-40
* Consult Release Notes on the NavCom web site for availability.