[TG] [TG11] Axiom Pro External GPS Antenna

[Tom - Raymarine - Moderator]

Hello carlmk,

Internal antennas, since they're surrounded by other electronics, operate in a higher-noise environment, and have to pick up their signal through the LCD and housing etc.. Axiom standard displays in particular have their antenna set a bit further back in the case compared to Axiom Pro and need a fairly good view of the sky.

We've also seen that - at least here in Australia and New Zealand - you can get a much less reliable fix when Differential mode is enabled, as is the default. This is because when the system uses Differential mode, it prefers to only use satellites for which the differential corrections are available, which means only the satellites which are visible from both your location and where the differential service is aimed at. In Australia/NZ, where there is no local SBAS service, we always recommend turning Differential off.

If you've got an Axiom Pro with recent software and a half-reasonable view of the sky and it's not getting a rock-solid GPS signal with at least half-metre accuracy (we typically get 0.6-0.8m accuracy with Differential off) then either there's another GPS in your system taking priority, or you have lots of RF interference (an increasingly common problem) or you have a fault with the Pro. I am completely confident in Pro's internal GPS. As I say, standard Axiom doesn't have it quite so easy because of where we've had to place the antenna, but they still work fine as long as they have a good sky view.

To anyone else reading this: if you have GPS problems with an Axiom or Pro, what we ask for here in Australia in order to understand the cause is:

1. clear, wide-angle photos of the mounting location (in relation to the rest of the boat and what's above and around it) of the MFD
2. photos or better video showing the contents of Home > GPS (top-left) > Satellites
3. A recording of the NMEA2000 data in the system, at the time when the poor-GPS problems are occurring (http://forum.raymarine.com/showthread.php?tid=6849)
   

If you can post this back here, we can usually see why the GPS isn't performing as we know they're capable of doing.

Tom