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AIS Receiver Range Record?
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 |
AIS Receiver Range Record?
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 |
AIS Receiver Range Record?
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AIS Receiver Range Record?
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 |
AIS Receiver Range Record?
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. |
AIS Receiver Range Record?
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 |
AIS Receiver Range Record?
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 |
AIS Receiver Range Record?
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 |
AIS Receiver Range Record?
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 |
AIS Receiver Range Record?
"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 |
AIS Receiver Range Record?
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 |
AIS Receiver Range Record?
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 |
AIS Receiver Range Record?
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 |
AIS Receiver Range Record?
"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 |
AIS Receiver Range Record?
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 |
AIS Receiver Range Record?
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 |
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