Antenna Location - NorthStar 941X Reference Manual

Antenna
Location
gps-only

antenna location

Page 104
Three antennas choices are available for your 941X: two for reception of
GPS-only signals (standard #AN145 and "active" #AN150), and one to
receive both GPS and DGPS signals (#AN190 combo antenna).
The antenna is a vital link between the 941X receiver and the outside
world. Aesthetics and easy access should be secondary to providing
strong and reliable GPS signals to the 941X receiver. You should select a
location for the antenna which meets the following requirements:
# The antenna should have a reasonably clear view of the horizon, but
be no higher than necessary (side-to-side motion of the antenna
caused by rolling of the vessel may degrade your SOG and COG
readings);
# The antenna must be out of the radiation plane of any on-board ra-
dar sets;
# The antenna must be lower than any INMARSAT communications
antenna;
# The antenna should be as far as possible from other high-power
transmitting antennas;
# Watch out for electromagnetic "shading" of antennas from rigging,
other vessels, shoreline buildings, etc. Secure the cable well (the
center conductor is solid wire).
Whereas a loran antenna should be mounted high on the vessel for best
performance, the GPS-only antenna should be mounted as low as possi-
ble and out in the open to avoid "shading" (placement of the antenna
where it is partially obscured by another object from the signals it must
receive). Don't mount the antenna on top of a tower or mast. Often the
bow or stern will provide a location where shading is minimized, while
serving to keep the antenna low. Be sure that any directional L-band
transmitting antennas (such as radar or satellite communication anten-
nas) can never point at the GPS antenna—its preamplifier is quickly de-
stroyed by such radiation.
9 — Installation and Interfacing 9 — Installation and Interfacing 9 — Installation and Interfacing 9 — Installation and Interfacing Rev. D