Antenna Cabling - NorthStar 961 Install Manual

SECTION TWO - Installation
Choosing the AN205-P combination antenna location
A "combo" GPS/DGPS antenna is available for applications involving
serious grounding problems (which create noise issues with the beacon
receiver), where optimum portability is required or when only a single
antenna is desired. The AN205-P doesn't require any ground, and is
portable—an advantage when it must be moved from one vessel to
another. The combo antenna should be located where it has a clear view
of the horizon, but isn't the highest point on the vessel. Keep the antenna
at least six feet away from objects that can "shade" GPS or differential
signals.
If poor GPS Signal-to-Noise Ratio (SNR) readings are obtained after the
system has been running for several minutes, check that you have the
proper length of cable, and verify the quality of the antenna location and
the quality and proper termination of the connectors. SNR readings
should be as high as possible. Values of 15 and higher are preferable;
anything below 10 could indicate poor reception.
Supplied with your 961/962 is a 50 foot-length of RG-59 coaxial cable to
About the
use with either the AN150 or the AN205-P. The length of coax cable to the

antenna cabling

AN150 antenna must be no less than 50 feet and no more than 100 feet; to
the AN205-P, no less than 20 feet and no more than 50 feet. When
installing antenna cable, don't bend it tightly in any places, and fasten the
cable along its length to avoid chafing or whipping of any kind. Coil up
any unused length of cable. Secure the cable well (the center conductor is
solid wire), and securely fasten all cable connectors. Be sure to use the
proper crimping tool for the antenna connector. Poor crimps will result in
the loss of GPS signals.
Whereas a differential or loran antenna should be mounted high on the
Installing the
vessel for best performance, the GPS antenna should be mounted as low
AN150 antenna
as possible and out in the open to avoid "shading" (placement of the
antenna where another object partially obscures the antenna from the
signals it must receive). If mounting on top of a tower or mast,
understand that the 961/962 will be affected by the pitch and roll of the
vessel. 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 antennas) can never point at the GPS antenna—its
internal preamplifier is quickly destroyed by such radiation.
961/962 INSTALLATION MANUAL Revision A Page 17