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Appendix C - Engineering Mode
GPS - GPS CDU Troubleshooting
GPS3 - Visible Satellite Information
Version 1.5
145
back-up battery. This will result in either a slow deterioration of
memory retention or it may abruptly dump all its memory.
Leica recommends the battery be changed every 2 to 3 years of opera-
tion by an authorized technical dealer. Marine electronics dealers or
radio shops will typically stock the replacement battery, Lithium type
CR2032, 3V.
This screen provides some basic information about the MX421 smart
GPS antenna performance, in that it is basically an extension of GPS1
screen. It tells you what satellites are available to track at the moment
under the PRN number. The signal strength of satellites under track is
in the second column labeled S/N. The weakest signal strength that the
GPS receiver can track is 25. However, any satellite with a signal
strength under 32 is considered troubled, and the GPS receiver will
not use that satellite in the navigation solution. Troubled satellites tend
to cause position jumps and greatly reduce the accuracy of the GPS
position fix.
The EL, AZ, and STA values represent the satellite's Elevation and
Azimuth, and Almanac Status respectively.
Low signal to noise (S/N) quality numbers may be an indication of
local interference from on-board electronic equipment such as Radar,
INMARSAT, VHF, SSB and other high power transmitters. Review
the installation of the entire system to ensure you have followed proper
procedures for cabling, power, and, most importantly, grounding and
antenna placement. The majority of these problems will be resolved
by better grounding and antenna location selection. Regarding ground-
ing, the water intake for the engine, or any other electrical ground
relying on the engine or generator for Earth ground, is not good for the
GPS and especially the beacon receiver.
Operation & Installation Manual
8/13/01, 11:07 AM
145
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Troubleshooting
