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.

Paul - I am assuming that the SR162 and SR161 have the same range, and
that either would have made the same long distance discovery. Is this
right? Or does the dual channel have a better chance of seeing
something far away?

Do you notice much difference in the speed of target information
acquisition between the two? Is the SR162 noticeably faster? My SR161
picks up targets and shows their speed quickly, but can take 5 or 10
minutes to fill in the name, size, destination, etc.

Thanks,

Gary

"Queeg" wrote in message
oups.com...

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.

Paul - I am assuming that the SR162 and SR161 have the same range, and
that either would have made the same long distance discovery. Is this
right? Or does the dual channel have a better chance of seeing
something far away?

Do you notice much difference in the speed of target information
acquisition between the two? Is the SR162 noticeably faster? My SR161
picks up targets and shows their speed quickly, but can take 5 or 10
minutes to fill in the name, size, destination, etc.

Gary,

I haven't compared the specs, but I am assuming that the sensitivity is
similar between the two units. I haven't done enough comparison to say for
sure, but the dual-channel unit ought to acquire the info more rapidly --
and that does seem to be the case from my brief experience. I will move my
older single-channel unit to my house (just for fun, and as part of my
development platform).

I want the dual-channel unit on the boat, because my antenna will be mounted
on the stern rail (not as good as on the mast), and I want to acquire the
signals ASAP. I, too, have seen the fast initial acquisition of the dynamic
data, which gets sent often, and the slow (or not at all) acquisition of the
static data, which is sent less frequently. The dynamic data is all you
really need for collision avoidance, but it is nice to get the ship name
(contained in the static data).

I will report back once I get more experience with the system. So far, the
SR162 seems very nice, although the price delta from the single-channel unit
is a bit steeper that I would like.

-Paul

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

Paul,

Tropospheric bounce sounds like the most plausable explaination. I was
just exercising alternative explaination. Since you brought it up, I
offer offer the SR161 - $189 and SR162 - $439 in our software store
http://www.navsoftware.com/sr161.php if anyone is looking for either of
these AIS receivers.

Paul wrote:
"Queeg" wrote in message
oups.com...

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.

Paul - I am assuming that the SR162 and SR161 have the same range, and
that either would have made the same long distance discovery. Is this
right? Or does the dual channel have a better chance of seeing
something far away?

Do you notice much difference in the speed of target information
acquisition between the two? Is the SR162 noticeably faster? My SR161
picks up targets and shows their speed quickly, but can take 5 or 10
minutes to fill in the name, size, destination, etc.

Gary,

I haven't compared the specs, but I am assuming that the sensitivity is
similar between the two units. I haven't done enough comparison to say for
sure, but the dual-channel unit ought to acquire the info more rapidly --
and that does seem to be the case from my brief experience. I will move my
older single-channel unit to my house (just for fun, and as part of my
development platform).

I want the dual-channel unit on the boat, because my antenna will be mounted
on the stern rail (not as good as on the mast), and I want to acquire the
signals ASAP. I, too, have seen the fast initial acquisition of the dynamic
data, which gets sent often, and the slow (or not at all) acquisition of the
static data, which is sent less frequently. The dynamic data is all you
really need for collision avoidance, but it is nice to get the ship name
(contained in the static data).

I will report back once I get more experience with the system. So far, the
SR162 seems very nice, although the price delta from the single-channel unit
is a bit steeper that I would like.

-Paul

Come off it , amateurs. I hold the record. Frequently get ships about 3200
miles away. Odd though - distance from here to the line where the Equator
crosses the Grenwich Meridian is about 3200 miles.

Joking apart, here in the UK, I have freqently found ships displaying duff
information, and I suspect that if their GPS is not working, they display
their position as zero degrees east and zero degrees north. In fact on
Saturday I saw a freighter goind up the Thames, but announcing she was in
the way to Liverpool. The previous week we were watching a Roll on Roll Off
ferry, 400/500 foot long with no AIS signal being broadcast. It is a
brilliant system, but always to be used with a pinch of salt.

Phil


"Paul" wrote in message
...
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

"Holger" wrote in message
...

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?

I finally decided to go to the source (regarding AIS repeaters in the San
Francisco area), so I sent email to the Training Director at the S.F. Vessel
Traffic Service. He tells me that there are currently no AIS repeaters in
the Bay area, nor are there any virtual aids to navigation at this time. I
asked nicely, and he offered to give me a tour of the VTS facility! I will
report back on any AIS info I learn from the visit.

Here is a link he sent me about AIS as used he
http://www.uscg.mil/d11/vtssf/Training/ais_main.htm There isn't much new,
but one of the documents listed contains the dock codes for the various
facilities around here. Now, if I see a destination like "US OAK 58", I
know where it is.

-Paul

Phil Stanton wrote:
Come off it , amateurs. I hold the record. Frequently get ships about 3200
miles away. Odd though - distance from here to the line where the Equator
crosses the Grenwich Meridian is about 3200 miles.

Joking apart, here in the UK, I have freqently found ships displaying duff
information, and I suspect that if their GPS is not working, they display
their position as zero degrees east and zero degrees north. In fact on
Saturday I saw a freighter goind up the Thames, but announcing she was in
the way to Liverpool. The previous week we were watching a Roll on Roll Off
ferry, 400/500 foot long with no AIS signal being broadcast. It is a
brilliant system, but always to be used with a pinch of salt.


They seem to congregate off the coast of Africa, don't they?

The position indicating no input is 91/181 and some software doesn't
check properly so it sets the position to 0/0

I once spotted a cruise ship going through Admiralty Inlet that jumped
sideways every couple of miles. While talking to a USCG guy I found
that they were experimenting with a new GPS system that wasn't working
all that well.

..cp

A follow-up to my original posting:

I have been using my Pocket PC program to capture and process the AIS data
being received by the SR162 receiver, and just wrote a quick program to
diaplay the tracks on Google Earth. Here is a link to my boat's blog, where
I have put some GE screen images, as well as the GE track-file:
http://www.sailvalis.com/wordpress_1/?p=129

By the way, I did visit the San Francisco VTS facility, and learned that
there are no AIS repeaters in the Bay area. This propagation is due to
tropo ducting for sure.

-Paul