AIS surprise

[Dsanduril]

I was finally able to do a little digging. The ham radio community uses AIS propagation as a proxy for 2m radio propagation. Since there are lots of AIS transmissions going on, and lots of stations to receive them, they can be used to evaluate DX propagation in the VHF bands. This is complicated by repeaters, if a signal is repeated then it defeats monitoring (for these purposes). So, a fair amount of effort went into identifying repeaters.

In S/W Australia the Cape Nelson Lighthouse (Portland), the Cape Jervis Lighthouse (Adelaide), and Point d’Entrecasteaux Lighthouse were all identified as almost certainly having repeater functions.

For GILow, if you really want to play with this, the ham community has a program called DX Aggregator (I have not used or tried the software) that is used to collect AIS information and distance to target. It specifically has a function to detect repeated signals (marked with an "(R)" ) so that they don't get included in the DX calculations.

Having said all of that, the western coast of Australia seems to be particularly known for ducting, with AIS signals reported regularly at 200-300km, and records out to ~3000km.