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

[Sonaia Maryon-Davis]

Mike,

We have used AIS since May 2004 and the range is variable as you say.
We have seen targets at over 100 miles and other times targets have
been only 10 miles away.  Mostly we will see them 20-30 miles out but
the detailed data on them (name of ship, destination, MMSI number
etc.) may not be received outside a 20 mile range and sometimes half
that distance.

Hope all is well with you.

Chris

On 1/13/07, Mike Maurice <mikem@yachtsdelivered.com> wrote:
> 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
>
> _____________________________________
> Capt. Mike Maurice
> Beaverton Oregon(Near Portland)
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