[TG] [TG11] No GPS Info on MFD GPS Status Page

[Tom - Raymarine - Moderator]

Do you know what pattern of flashes was showing on the RS150 when you saw the red LED? That pattern gives useful diagnostic information. The LED sequence for 'no GPS fix' is a single quick red flash every 3 seconds: is this what you were seeing?

Usually, red LEDs on RS150s indicate a supply voltage problem, either marginal low voltage or, more commonly, an unstable or high voltage from a misbehaving charging source. I can't remember the last time I saw an actually faulty RS150 except where they've been mounted incorrectly and had the breather on the bottom sitting in its own private puddle.

Yes, SOG is calculated inside the antenna and comes from a measurement of distance between recent position fix locations. All of the things you're describing except possibly the red LED (depending on what LED sequence you saw) come from poor GPS position fix quality. Unfortunately photos of the chart or an incorrect COG, SOG or position don't tell us anything about the cause of the poor fix.

Causes of poor GPS fix essentially boil down to:

1. a faulty antenna. Since replacing the antenna has not fixed the issue - as I say, RS150s pretty much never fail - then we can rule this one out in your case.
2. a poor view of the sky
3. some source of radio frequency (RF) interference which is drowning out the very weak radio signals from the GPS satellites (when I say weak signals, picture trying to see a 25W incandescent light bulb from 30,000km away.)
   

Assuming the RS150 is mounted out in the open where it has a clear view of the sky all around (is this the case? Please send photos of the mounting location), the problem is probably RF interference. There is more information about this on the FAQ that I linked to before. RF interference can come from all sorts of devices, not just those that are intended to transmit radio.

Unfortunately it's not easy to prove this is the case with the equipment you have on board. Seeing what satellites are in view over time with what signal levels can give good clues, but you've already said that you aren't seeing this in your system (in Menu > GPS Status) because it isn't passed through by the convertor. You would need a more recent, STNG-compatible MFD to be connected for this, which is something your dealer could usefully have done. Alternatively, a specialist technical dealer would need to visit the boat with a spectrum analyser that can scan the GPS frequencies at around 1.5GHz for RF noise. Not many dealers have the tools and expertise for this unfortunately, but if you can let me know where you are I can see who locally might be able to help.

Alternatively, you could turn the vessel battery isolators and all on-board systems off and temporarily power the E80 and RS150 via a completely independent battery and see how the GPS fix is then. Still, without GPS fix status it will be hard to clearly see the impact of this.

Regards,
Tom