Disappearing AIS targets

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Last year we replaced much of our electronics. New instruments include Es95 MFD, Ray60 VHF, Raymarine Digital Radar. This is interfaced to our existing SmartPilot S2, and AIS 250. We also have a new VHF antennae.

The antennae is run to the AIS and then connects from the AIS to the VHF. Radio functionality is fine.

In another thread I reported that the MFD would lose the name and other information on targets while a different navigation program (OpenCPN) would not. It was determined that the OpenCPN has a cache of mmsi/names file, whereas the Es does not. Feature request was made.

This is a different problem.

I have come to realize that targets are DISAPPEARING from the Es95 but not the OpenCPN program. Last week I was sailing across SF Bay and AGAIN had a target DISAPPEAR from the display, while it did continue to display on the OpenCPN software being fed the same data. This was a large ship leaving from east of us and heading west out the Golden Gate Bridge.Their course was across our path and I was paying attention to the vector I set on the MFD. Then it disappeared. We have had situations where fog sweeps into SF Bay -- it happens. Having a target disappear in the fog would be many times worse than disappearing in good daylight conditions. Both are bad.

Configuration . . . the antennae is at the top of the mast and a cable goes to the base of the mast where it connects to a cable that was already in place in the previous system. That goes to the AIS 250, and a short cable connects from the AIS to the Ray 60. I have two pairs connected to the AIS 250 Nema Out. One to the Raymarine system and another to a "MiniPlex Lite" and then a COM/USB connection to a computer.

It's difficult to document a disappearing target because I can't memorize all targets on display and one then missing, let alone do a screen shot before it disappears. None-the-less, attached are two screenshots from the MFD. The area is the entrance to San Francisco Bay. In Dump006 at 21:36 there is no AIS target in the entrance to SF Bay, but in Dump007 at 21:38 there is . . . two minutes later! My recollection is that I had seen this AIS target before it disappeared. In any case we regularly view AIS targets out in the shipping lanes (and do look for them as they can be on us sooner than one might think). I'm hard pressed to think the second screen shot was the first we had seen of this ship.

I'm finding that the AIS has become more of a troubleshooting problem than a help in navigation. I need find out what's going on soonest.

Robert