[PUP] Ice Dancer 01/04/07: Following the Peruvian and Chilean coast south

[Mike Maurice]

The range of AIS is not set in stone. 50 miles is a bit of a stretch 
under most conditions. However, I think I recall seeing a contact once 
at 100 miles. Since the frequencies are near 170 mhz. the predictable 
range is line of sight, antenna to antenna plus a little for some 
bending around the earth's curvature.

Any time a contact shows up beyond that "predictable" distance it has to 
be due to atmospherics, generally known as a tropospheric duct. At 170 
mhz such ducts can be on the order of several hundred to a thousand 
miles or so, especially in the tropics or semi tropics.

In a dry atmosphere, the range will almost always be limited to line of 
sight.


Regards,
Mike

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Capt. Mike Maurice
Beaverton Oregon(Near Portland)