Marine GPS aerials should be mounted clear of fly bridge and tuna tower frames, deck equipment and other radio aerials. Where possible the aerial should have as wide a field of view as practicable, while being located as low as possible. In installations that have a tower with mounted radar, ensure that the GPS aerial is not within the radar antenna beam spread. If the aerial cannot see the satellite then you will get poor reception. In yachts bad installation is a principal cause of bad position fixes. I have lost count of the number of antenna’s on stern rails that are shadowed by masts and spars and so on, or have been pushed over from nominal vertical positions because ropes have caught them and moved them, without anyone noticing.
Marine GPS cables need to routed so as to avoid interference. Power supply cables should be routed as far as practicable from equipment cables carrying high currents. Aerial cables should also be routed well clear of areas where they can be mechanically damaged. It is extremely important for the aerial cable not to be kinked, bent, or placed in any tight bend radius and if it transits through stainless steel stern rail tubing the entry points need to be covered to avoid chafe. Bending of cables has the effect of narrowing the dielectric gap within the coaxial cable, which may cause signal problems. Ensure that all through-deck glands are high quality in that they properly protect the cable. Do not shorten or lengthen an aerial cable unless your manufacturer approves it.
Ensure that all connectors are properly inserted into the GPS receiver. Ensure that screw-retaining rings are tight, because plugs can work loose and cause intermittent contact. The coaxial connector from the aerial into the receiver should be rotated properly so that it is locked in. External aerial connections should be made water resistant where possible. Use of self-amalgamating tape is a good method for doing this. If you have to remove and refit an aerial connector, ensure that you use considerable care and assemble the connector in accordance with the manufacturers’ instructions.
The ground connection provided with the system must be connected to the RF ground system or negative supply polarity depending on manufacturers’ recommendations, so read your installation manual carefully and do it correctly.
A clean power supply is essential to proper operation. Use either an in-line filter or install suppressors across “noisy” motors and alternator. The power supply should not come from a battery used for engine starting, or used with any high current equipment such as the trolling motor or a powered deck winch. When they operate surges and spikes are generated which cause issues with the GPS. Look for more great information at fishing and boats.