NavCom SF-3040 Rev.F - Manual (Page 96)

SF-3040 Product User Guide
– Rev. F
4-94
antennae. The wavelength of L2 is 0.244m and
L1 is 0.19m. The minimum acceptable separation
between antennae is 1m (39 in), which provides
6dB of isolation. For 10dB of isolation, separate
the GNSS antennae by 2.5m, and for 13dB of
isolation (recommended) separate the antennae
by 5m.

Active antennae
(those with LNA’s or amplifiers)
create an electrical field around the antenna.
These radiated emissions can interfere with other
nearby antennae. Multiple GNSS antennae in
close proximity to each other can create multipath
and oscillations between the antennae. These
add to position error or the inability to process the
satellite signals.

Most antennae 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
(which translates into signal strength) throughout
the entire elevation tracking path.

Map obstructions above the horizon using a
compass and inclinometer. Use satellite prediction
software with a recent satellite almanac to assess
the impact on satellite visibility at that location
(available on NavCom’s web site).

A clear line of sight between the antenna and the
local INMARSAT satellite is required to track the
StarFire™ signal. INMARSAT satellites are geo-
synchronized 35,768kms above the Equator,
currently at Longitudes 15.5

West, 098

West,
142

West, 025

East, 109

East, and 143.5

East.
An inclination and bearing estimation tool is
available on NavCom’s website to aid in
determining potential obstructions to the
StarFire™
signal.