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)

Of course, I also moved my whip antenna from the deck railing to the roof,
which has to help a tiny bit. I am at about 1000ft elevation, 4 miles from
the coast, and 40 miles north of the Golden Gate Bridge. Still, this is so
far beyond line-of-sight that it has to be tropospheric ducting.
Occasionally, VHF signals make the trip from Hawaii to California (about
2000 miles), and an interesting by-product of widescale AIS deployment is
that there are now all these AIS "beacons" spread out all over the oceans,
running continuously.

AIS DXing - who holds the record?

-Paul

Paul, this is very impressive. Is there a chance noaa is repeating
traffic from a bouy in your area?

-Mark


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)

Of course, I also moved my whip antenna from the deck railing to the roof,
which has to help a tiny bit. I am at about 1000ft elevation, 4 miles from
the coast, and 40 miles north of the Golden Gate Bridge. Still, this is so
far beyond line-of-sight that it has to be tropospheric ducting.
Occasionally, VHF signals make the trip from Hawaii to California (about
2000 miles), and an interesting by-product of widescale AIS deployment is
that there are now all these AIS "beacons" spread out all over the oceans,
running continuously.

AIS DXing - who holds the record?

-Paul

wrote in news:1158280930.156369.191480
@h48g2000cwc.googlegroups.com:

Paul, this is very impressive. Is there a chance noaa is repeating
traffic from a bouy in your area?

-Mark



NO bouy has, or ever will have, an AIS system in it. There MAY be an AIS
repeater in his area, but it will be on a real tower, not a bouy. To mark
the bouy's position, a shore station may send the bouy's information, which
AIS is designed to do but, of course as usual, America is 20 years behind
Europe in implementing everything, any more.

To make a bouy show up on your AIS, all the shore station does is transmit
its data. The position of the actual transmitter has no bearing,
whatsoever, on where anything shows up, like a radar return does. It's
just DATA...even bad data as someone reported a ship traveling overland the
other day...miles from its position.

Caveat Emptor

--
There's amazing intelligence in the Universe.
You can tell because none of them ever called Earth.

wrote in message
oups.com...
Paul, this is very impressive. Is there a chance noaa is repeating
traffic from a bouy in your area?

-Mark


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)

Of course, I also moved my whip antenna from the deck railing to the
roof,
which has to help a tiny bit. I am at about 1000ft elevation, 4 miles
from
the coast, and 40 miles north of the Golden Gate Bridge. Still, this is
so
far beyond line-of-sight that it has to be tropospheric ducting.
Occasionally, VHF signals make the trip from Hawaii to California (about
2000 miles), and an interesting by-product of widescale AIS deployment is
that there are now all these AIS "beacons" spread out all over the
oceans,
running continuously.

AIS DXing - who holds the record?

-Paul

Mark,

The "AIS repeater" thought did occur to me, and I haven't researched it, but
I am not aware of any AIS repeaters in the area. The DX signals do seem to
be most prevalent when the local "marine layer" (fog) comes in in the
evening, and I am assuming that the ducting, if that is what's really going
on, is occuring when there is stratification in the lower atmosphere. Also,
my best DX was from the "Ikaragu", at lat 30.57N lon 132.56W, which is about
630 NM out from the nearest coastline. I would be very surprised if there
were repeaters within LOS of that point, and if so how would they send the
signal back to the mainland? They could use satellite, but that seems
unlikely. Further speculation on my part would be silly...

Does anyone know if there are any AIS repeaters currently operational? This
technology is so cool, but I have to remind myself occasionally that it
isn't infallible -- see my recent posting about AIS position errors.

-Paul

Larry, I have to disagree. Please see the the following pdf file
[http://www.uscg.mil/d13/units/vts/psvts.html] and notice the bouy in
the diagram acting as a repeater. AIS is good for everyone whether in
Europe, the Americas or anywhere else. I'm Looking forward to having
Galileo as a positioning option in the comming years, but right now i'm
sure they are using GPS

Larry wrote:
wrote in news:1158280930.156369.191480
@h48g2000cwc.googlegroups.com:

Paul, this is very impressive. Is there a chance noaa is repeating
traffic from a bouy in your area?

-Mark



NO bouy has, or ever will have, an AIS system in it. There MAY be an AIS
repeater in his area, but it will be on a real tower, not a bouy. To mark
the bouy's position, a shore station may send the bouy's information, which
AIS is designed to do but, of course as usual, America is 20 years behind
Europe in implementing everything, any more.

To make a bouy show up on your AIS, all the shore station does is transmit
its data. The position of the actual transmitter has no bearing,
whatsoever, on where anything shows up, like a radar return does. It's
just DATA...even bad data as someone reported a ship traveling overland the
other day...miles from its position.

Caveat Emptor

--
There's amazing intelligence in the Universe.
You can tell because none of them ever called Earth.

Sorry, here is the direct link to the PDF -
http://www.uscg.mil/d13/units/vts/AISSRSFinal.pdf

Larry wrote:
wrote in news:1158280930.156369.191480
@h48g2000cwc.googlegroups.com:

Paul, this is very impressive. Is there a chance noaa is repeating
traffic from a bouy in your area?

-Mark



NO bouy has, or ever will have, an AIS system in it. There MAY be an AIS
repeater in his area, but it will be on a real tower, not a bouy. To mark
the bouy's position, a shore station may send the bouy's information, which
AIS is designed to do but, of course as usual, America is 20 years behind
Europe in implementing everything, any more.

To make a bouy show up on your AIS, all the shore station does is transmit
its data. The position of the actual transmitter has no bearing,
whatsoever, on where anything shows up, like a radar return does. It's
just DATA...even bad data as someone reported a ship traveling overland the
other day...miles from its position.

Caveat Emptor

--
There's amazing intelligence in the Universe.
You can tell because none of them ever called Earth.

Paul,

I have received AIS data in the Seattle VTS zone repeated from bouys. I
think the SF area has it as well. Enough AIS for me tonight. I have to
get cracking on my handheld sail racing software

Cheers,
-Mark


Paul wrote:
wrote in message
oups.com...
Paul, this is very impressive. Is there a chance noaa is repeating
traffic from a bouy in your area?

-Mark


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)

Of course, I also moved my whip antenna from the deck railing to the
roof,
which has to help a tiny bit. I am at about 1000ft elevation, 4 miles
from
the coast, and 40 miles north of the Golden Gate Bridge. Still, this is
so
far beyond line-of-sight that it has to be tropospheric ducting.
Occasionally, VHF signals make the trip from Hawaii to California (about
2000 miles), and an interesting by-product of widescale AIS deployment is
that there are now all these AIS "beacons" spread out all over the
oceans,
running continuously.

AIS DXing - who holds the record?

-Paul

Mark,

The "AIS repeater" thought did occur to me, and I haven't researched it, but
I am not aware of any AIS repeaters in the area. The DX signals do seem to
be most prevalent when the local "marine layer" (fog) comes in in the
evening, and I am assuming that the ducting, if that is what's really going
on, is occuring when there is stratification in the lower atmosphere. Also,
my best DX was from the "Ikaragu", at lat 30.57N lon 132.56W, which is about
630 NM out from the nearest coastline. I would be very surprised if there
were repeaters within LOS of that point, and if so how would they send the
signal back to the mainland? They could use satellite, but that seems
unlikely. Further speculation on my part would be silly...

Does anyone know if there are any AIS repeaters currently operational? This
technology is so cool, but I have to remind myself occasionally that it
isn't infallible -- see my recent posting about AIS position errors.

-Paul

wrote in message
oups.com...
Sorry, here is the direct link to the PDF -
http://www.uscg.mil/d13/units/vts/AISSRSFinal.pdf

Larry wrote:
NO bouy has, or ever will have, an AIS system in it. There MAY be an AIS
repeater in his area, but it will be on a real tower, not a bouy. To
mark
the bouy's position, a shore station may send the bouy's information,
which
AIS is designed to do but, of course as usual, America is 20 years behind
Europe in implementing everything, any more.
[...]

Larry, Mark, it sounds like you're both right. The buoy repeater described
in the link is surprisingly like what I had conjectured in my previous
posting -- it is more of a remote receiver (transceiver?) than a true
repeater. I haven't been able to find details of *any* type of repeater
deployment in the San Francisco area, but I assume that there may be some in
operation, used to fill in radio dead-spots.

Still, as far as explaining the reception I was getting (from a ship 673 NM
distant), I can't see any reason for wanting to repeat that signal in the
S.F. Bay area. S.F. VTS may be interested in what a distant remote receiver
buoy is hearing, but they would get that data through their land network,
and would be unlikely to re-transmit it over the air. Tropospheric Ducting
is my theory, and I'm sticking to it!

-Paul

During recent good propagation conditions I have decoded targets a good 350 nm away - with a receiver in Norway right across the North Sea to the Scottish coast and along the coast of Belgium. Equally impressive where stations received across 200nm of land -right across Sweden....

The use of repeaters sounds interesting, anyone knows some details?

Holger

You win the cigar... 'Ducting' or 'Tropo' as we hams often call it
acts just like the furnace ducts in your house in guiding the air that
wants to spread everywhere to where we want...
With VHF radio signals sharp temperature and density gradients in the
atmosphere will act just like a metal duct, forming a roof and a floor
and causing the radio signal to skip/bounce/reflect as it goes along
and confining it like inside a heating duct (actually it refracts but I
don't want to go off into theory here) forming a roof and a floor...
Usually the floor is the ocean or the ground and the roof is a few
thousand feet in the air... Other times it is another air discontinuity
layer below the upper one and when this happens the signals will rattle
along for thousands of miles losing very little energy... If you are
in the right location when the signal finally exits the duct you will
hear strong signals from far off...
When hams discovered this effect in the 50's and 60's (the big time
physicists of the government denied any such thing existed) the first
evidence came from 2 meter ham signals being ducted between Hawaii to
California (how's that for line of sight vhf?) But, to transmit or
receive these signals the hams at each end had to go up the coastal
mountains (usually in their car) to the correct altitude and that duct
could be as narrow as a hundred feet in height... Higher or lower and
you were out of the duct... It was first noticed by hams who just
happened to be driving the mountain road and suddenly began hearing
signals from Hawaii - a happy accident...
Anyway Paul, a good call on your part...

denny / k8do