Different AIS receivers showing different targets

[Midnight Drifter]

I have a NASA AIS 'Radar', and have recently bought a Quark-Elec wireless AIS receiver which sends AIS data by WiFi to a tablet running Marine Navigator.
The NASA receiver seems to display all ships, but it does not display any navigational aids which transmit AIS, such as lighthouses.
The Quark/Marine Navigator set-up does display AIS navigational aids but misses some ships. For example, yesterday there were 4 ships in the vicinity for about an hour, but one of them was never displayed by Quark/Marine Navigator but was displayed by the NASA receiver for the whole time.
Both receivers are connected to the same aerial, using a coax splitter, so must be receiving the same AIS signals. Why do they not display the same targets?

 

[laika]

Older units don't understand AtoNs so I'd be guessing that's what the NASA unit's issue is (which doesn't explain the other problem).

 

[Refueler]

I had similar other day .....

When going from Yacht Club to home mooring after lift out repairs ... pal of mine was using his Smartphone App and had AIS targets showing up .... Dredger alongside town quay ... Harbour workboat in river ... but nothing of my AIS tx. (He was set for A + B).
My AIS showed workboat but not Dredger .... my Plotter also set for both A + B.

 

[RobbieW]

I had similar other day .....

When going from Yacht Club to home mooring after lift out repairs ... pal of mine was using his Smartphone App and had AIS targets showing up .... Dredger alongside town quay ... Harbour workboat in river ... but nothing of my AIS tx. (He was set for A + B).
My AIS showed workboat but not Dredger .... my Plotter also set for both A + B.

This in particular is not comparing like for like. The app will be displaying the results of shorebased AIS recievers inputting data for the app, your onboard reciever is relying solely on the boat aerial and whatever your reciever makes of signals recieved

 

[Refueler]

This in particular is not comparing like for like. The app will be displaying the results of shorebased AIS recievers inputting data for the app, your onboard reciever is relying solely on the boat aerial and whatever your reciever makes of signals recieved

I am well aware of the difference of the two systems .... it was a post to add to OP's not to explain it ...

 

[pvb]

The Quark/Marine Navigator set-up does display AIS navigational aids but misses some ships. For example, yesterday there were 4 ships in the vicinity for about an hour, but one of them was never displayed by Quark/Marine Navigator but was displayed by the NASA receiver for the whole time.

Was the one ship moving or stationary? Could the app be set to ignore stationary targets?

 

[Midnight Drifter]

Was the one ship moving or stationary? Could the app be set to ignore stationary targets?

All the ships were moving. Also, the same issue has happened on other occasions.

 

[PaulRainbow]

All the ships were moving. Also, the same issue has happened on other occasions.

The NASA AIS most likely doesn't show AtoNs dues it its age and/or simplicity (as suggested above).

I'd try a different app' on the tablet to determine if the tablet issue is the Quark device or the app' itself.

Do you have the Quark AIS receiver with a built in multiplexor and if so, is it multplexing, or just being used for AIS ? If the latter, it could be getting overloaded with data, i've seen this happen before with multiplexors, including Quark devices.

 

[Midnight Drifter]

The NASA AIS most likely doesn't show AtoNs dues it its age and/or simplicity (as suggested above).

I'd try a different app' on the tablet to determine if the tablet issue is the Quark device or the app' itself.

Do you have the Quark AIS receiver with a built in multiplexor and if so, is it multplexing, or just being used for AIS ? If the latter, it could be getting overloaded with data, i've seen this happen before with multiplexors, including Quark devices.

The Quark is just being used for the AIS.
Thanks for the suggestion. I'd like to use the AIS data with Memory Map on a tablet but apparently it does not cope with AIS data via WiFi with GPS data coming from the tablet.

 

[PaulRainbow]

The Quark is just being used for the AIS.
Thanks for the suggestion. I'd like to use the AIS data with Memory Map on a tablet but apparently it does not cope with AIS data via WiFi with GPS data coming from the tablet.

That may be becuse you're sending GPS data with the AIS via wifi, so two GPS sources. Can you turn the tablet GPS off and have GPS and AIS via wifi ?

 

[Midnight Drifter]

I am only sending AIS data via WiFi and do not have the kit to add GPS to it. Marine Navigator works with them coming from different sources (which is preferable, because it uses the GPS capability of the tablet). Memory Map does not.

 

[Bilgediver]

I have a generic blackbox AIS receiver here that can be connected to Hyperterminal etc to set parameters.One parameter is maximum range distance to target. Is yours set at 5 mi!es if this is possible there.

 

[KompetentKrew]

My spider sense says it's an aerial problem. Maybe the signals are weaker when a coax splitter is used, and the Nasa unit is more sensitive. Try the Quark-Elec on its own.

 

[Midnight Drifter]

My spider sense says it's an aerial problem. Maybe the signals are weaker when a coax splitter is used, and the Nasa unit is more sensitive. Try the Quark-Elec on its own.

I'll try that, thanks, and maybe try swapping which side of the splitter feeds which device.

 

[Midnight Drifter]

I have a generic blackbox AIS receiver here that can be connected to Hyperterminal etc to set parameters.One parameter is maximum range distance to target. Is yours set at 5 mi!es if this is possible there.

Neither system has a maximum range, and the missing ships have remained missing even when closer than others that show up.