AirNav ShipTrax > AirNav ShipTrax Discussion

ShipTrax

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dorsetderek:
Will there be any advantage using a larger aerial with the ShipTrax?, I live quite close to the sea, dorsetderek

Budgie:
It's not so much about the size of the aerial as the height and making sure it's the correct type.
AIS uses Marine VHF frequencies and VHF is "line of sight", which basically means if you can see the target then you can hear it.
To get more range then the higher the aerial the better.
I don't know about ShipTrax but any normal AIS unit will work fine with a standard marine antenna.

tarbat:
I find that you don't need clear line-of-sight, just "nearly" line-of-sight.  I can't see Invergordon, there are hills (and houses) in-between, but I get a good signal from ships there.

And to be honest, I tried a couple of marine antennae, and actually found that my standard £30 discone antenna gave much better reception of AIS.  I never really understood why, but I get great reception with a cheap discone mounted in the loft, with concrete roof tiles blocking the signal.

That's using the ShipTrax receiver.  Using a Comar AIS-2-USB isn't anywhere near as successful though!!

jannuh:
Get here the best results with a combi-antenna for 144/430 mHz, it's abt. 2.25 in length, mechanical very strong; it is now abt. 15 years in use on rooftop and still standing strong.

Tried also a yagi antenna, also a combi for 144-430 mHz, nice if you have the shiptraffic in one direction.

The difference between a (cheap) general scanner antenna and a professional marine antenna will be mainly its mechanical stability of the last one.

Budgie:
The atmospherics also play a part in the range that can be obtained.
During summer high pressures I've managed to pick up AIS base stations in the Faeroes, that's something like 250 miles.
I currently use something similar to this Metz Manta which is mounted on my anemometer mast on the chimney of the house at about 45m ASL.
You can see the range map of what I get with this and my Comar AIS-2-USB on MarineTraffic.
Note: The reception to the far south, Kyle of Lochlash, is most likely the local Coastguard helicopter rather than shipping. ;-)

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