AIS propagation

[Boz]

I'm sat in North Fambridge Marina looking at AIS targets off the Belgium Coast (range 106 NM). I've never seen that before, from here usually only have a range of less than 20 miles (Thames Estuary and London. Must be unusual VHF propagation?

 

[sarabande]

anomalous propagation, aka tropospheric refraction.

There are a few VHF enthusiasts who think that these atmospheric conditions preface an earthquake.

 

[Gargleblaster]

I've found that in isolated parts of the ocean where there isn't much shipping that you can get AIS reception from quite a way away. The best was in the Southern Ocean picking up a ship 900 miles away. I have regularly picked up vessels and buoys out to 300 miles. I depend on the security of my sleeping that I will pick up anything 50 miles away.