AIS shows many long distance targets

[Paul L]

An AIS aid to navigation does not need to be located at the ATON, and usually isn't. It is broadcast from some other location but broadcasts the position of the ATON. So the distance from the ATON is not relevant to how far the signal can be seen.

[swampbush]

Originally Posted by Paul L

An AIS aid to navigation does not need to be located at the ATON, and usually isn't. It is broadcast from some other location but broadcasts the position of the ATON. So the distance from the ATON is not relevant to how far the signal can be seen.

But in this case the acma link is to the coordinates of the transmitter. For a remote location I think it would be out of range to local traffic if it wasn't on site at the island or repeated locally.

[RaymondR]

Ducting, I have been moving down the same coast for the last few weeks and heard VMR's from hundreds of miles south from north of Dunk Island.

In southern Western Australia it's not that uncommon to hear Japanese stations working ships in port on the VHF channels. I think they call it trans equatorial ducting and it happens in other parts of the world.

[Hartleyg]

Originally Posted by DeepFrz

Repeaters do not work by transmitting the same information out on the same frequencies. They would re transmit the information out on a different frequency that an AIS Transceiver would not receive.

Actually, the correct word would be "digipeater", rather than repeater - basically a device that hears & records AIS signals, then sends them out again on one of the two AIS channels. If you located one (or more) in high places (mountaintop or high tower), it would facilitate long-distance AIS coverage.

See: PMAPI AtonisPro-R AIS Repeater
also: https://navcen.uscg.gov/?pageName=AISworks Note that the 5th paragraph refers to AIS repeaters.



That said, I think it's more likely that propagation is causing the OPs event.


Hartley
S/V Atsa

[conachair]

Originally Posted by Hartleyg

That said, I think it's more likely that propagation is causing the OPs event.

Handy check is to have a look at a nearby marinetraffic station details, area covered in square Km will give a good indication if some tropospheric enhancement is going on.
https://www.marinetraffic.com/en/ais.../stations/2324

Also, if you stick an ais message into one of the online decoders and it will show if the message has been repeated or not.

AIS VDM & VDO Message Decoder - Maritec Solutions

[KeelMe]

I might have to come up there and see this.