Paul wrote:
I just received a SR162 dual-channel AIS receiver, which I will be using on
my sailboat -- the old single-channel SR161 will end up at home. I've been
testing at my house it these last couple of days, and have been amazed at
the range I have been getting. I've seen many ships 100 to 200 nautical
miles from my position, and last night saw one at 492 miles, and another at
673 miles" (this one was "Ikarugu", a freighter heading to Long Beach, CA)


That's pretty close to the furthest one I've seen. We were using high
sensitivity receivers and a directional yagi antenna pointed SW from
near Seattle. I saw several reports from 650nM out, off the coast of
California. With a good antenna and receiver 200nM reports are no
problem. You don't get every one but 30% is enough to let you know who
is where.

The USCG is really interested in long range AIS, they have done a whole
bunch of experiments relating propagation to the state of the
troposphere. Here is a really good site with graphs:

http://www.dxinfocentre.com/tropo.html