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Author Topic:   ICOM AIS Receiver

jimh posted 01-05-2009 08:10 PM ET (US)
ICOM have announced the MXA5000 AIS Receiver. Details are limited to those contained in the press release:
http://www.icomamerica.com/en/media_events/news/NewsArticle. aspx?id=200809
ICOM's release refers to the MXA5000 as a "Class B Receiver" but this designation makes no sense. In the automatic identification service both Class-A and Class-B transponders use mostly the same protocols and transmit on the same frequencies. ICOM also refers to the device as having a "full duplex" receiver, which I interpret to mean that it receives simultaneously on both AIS channels.
The MSRP is anticipated to be about $500. The MXA5000 contains an antenna switch which permits the vessel's existing VHF Marine Band radio antenna to be used as a receive antenna for the AIS receiver. Outboard devices that provide this function can cost as much as $250. This mitigates the cost of the MXA5000 somewhat. Considering the built-in multiplexer and the dual-receive capability, the ICOM's price of $500 is not excessive, particularly when compared to some other brand name receive-only devices which have been offered at $800.
The MXA5000 AIS receiver should be available in a few months.
towboater posted 01-06-2009 01:25 AM ET (US)
Quote from the Icom promo...
"AIS is used by ships and Vessel Traffic Services for identification and locating vessels."
Why would someone need AIS on a recreational Boston Whaler?
For whatever good reason a BW owner may have, my fear is that AIS may lull a Recreational Boater into a false sense of security. Beware, there are still many large vessels that are not required to transmit AIS signals you should constantly watch out for.
Otherwise, the Icom looks like a nice setup. Thx Jim.
mk
Chuck Tribolet posted 01-06-2009 08:05 AM ET (US)
We're going to see AIS receivers built into VHF raadios.
It can be done for < $25 mfg cost, perhaps a lot less.
Chuck
jimh posted 01-06-2009 08:18 AM ET (US)
Why would someone need an AIS receiver on a Boston Whaler? For the same type of reason that someone needs a $4,000 color display, precision fix GPS receiver, and digital side scan SONAR. It's another electronic gizmo. You don't need any of them, but that seldom stops people from having them.
Regarding the price of an AIS receiver, the cheapest is still about $200. I have a listing at
http://continuouswave.com/whaler/reference/AIS.html
jimh posted 01-06-2009 08:35 AM ET (US)
Chuck--Given the costs of shipping, marketing, distribution, sales, and so on, it may very well be that a device selling for around $500 has an actual manufacturing cost of about $25.
As for incorporating an AIS receiver into a VHF Marine Band Radio, it is possible, but it is not as trivial as you might think. Let's look at what is already in a VHF Marine Band radio:
--25-watt FM transmitter, frequency agile
--FM receiver, voice modulation, frequency agile
--DSC receiver, data modem, dedicated to DSC channel
--DSC control system compliant with Class-D specification
--NMEA serial data interface, input and output
In an AIS receiver we would add:
--AIS receiver, data modem, first channel
--AIS receiver, data modem, second channel
--serial data interface
The radio would have four receivers, all capable of simultaneous and independent reception, as long as the transmitter was not operating. Providing four receive channels will take some careful engineering. They're all connected to the same antenna, and there is the possibility of some mutual interference. It's not impossible to do, but it will take careful design.
At the moment I would guess that some of the cost represents licensing of some fundamental software or processing from a third party. Not all the manufacturers may have taken the time to engineer and develop all the details of AIS reception themselves. One firm in the U.K. seems to be a leader in AIS development.
Chuck Tribolet posted 01-06-2009 12:39 PM ET (US)
It's entirely possible that they are using software receivers
now, so the four "receivers" would share a single wide-band
A-D converter. No interferance problems. In any event,
they've already solved the interferance problems for two
receivers.

Chuck
bluewaterpirate posted 01-06-2009 10:41 PM ET (US)
Here's some more data on the unit
http://www.icomamerica.com/en/products/marine/navigation/mxa5000/ default.aspx
bluewaterpirate posted 01-06-2009 10:51 PM ET (US)
You can place your order.
http://www.docksideradio.com/AIS%20MXA-5000.htm
jimh posted 01-07-2009 09:02 AM ET (US)
Hey--the price went up $100 already! (The unit is advertised at $600; the press release mentioned $500.)
towboater posted 01-10-2009 11:03 AM ET (US)
On why a recreational boater would need AIS as a navigational tool (beyond a luxury toy), it has occurred to me...
AIS info could be very helpful to separate known and unknown targets in a congested area.
For example;
You are anchored or running near the edge of a congested navigable channel in deep water. One ship or Towboat may be overtaking another headed in your direction but still too far away to see the names. AIS would confirm who is who and you would quickly understand the passing situation without needing to ask.
mk
jimh posted 01-10-2009 11:17 AM ET (US)
I just noticed that you can purchase an ACR Nauticast-B AIS Class-B Transponder system from various resellers for about $750. This includes:
--AIS dual channel receiver
--AIS Class-B transponder (2-watt)
--GPS receiver
--GPS receiver antenna
--AIS transmit-receiver antenna
--NMEA dual serial ports
This is a FCC certified Class-B transponder which will transmit your vessel identity to others, as well as a dual channel receiver, and a GPS receiver. It also includes two antennas!
The price of the ICOM receive-only AIS product seems a bit excessive in comparison.
Cf.: http://store.milltechmarine.com/acraisproducts.html
Olsonist posted 01-13-2009 12:10 PM ET (US)
At $500 (or less) and with a built-in splitter [the ICOM AIS MXA5000] is 60% less than the NAIS-300-L Class B AIS Transponder and splitter at about $1,300.
Lower power, smaller footprint, better integration. What's not to like? Well, NMEA 2000 would have been nice. It might still be.
bluewaterpirate posted 01-13-2009 12:21 PM ET (US)
[The ICOM MXA5000] is selling for $450.
Better overview of connectivity.
http://albums.phanfare.com/4892322/2160052#imageID=57961608
jimh posted 01-13-2009 08:00 PM ET (US)
The ICOM MXA5000 is just a receiver; it is not a transponder. It ought to cost a lot less than a certified Class-B transponder.
jimh posted 01-13-2009 08:04 PM ET (US)
It is not clear if there is any AIS receiver that has a NMEA-2000 interface. The RAYMARINE AIS500 transponder may have a NMEA-2000 interface. It is noted as having a SeaTalkNG interface, which is Raymarine's name for NMEA-2000. See:
http://www.jgtech.com/shop10.htm
bluewaterpirate posted 01-13-2009 11:47 PM ET (US)
Spent four hours on the water last weekend using two different AIS systems. The biggest problem was the periodic loss of data from vessels in our immediate area. The other issue was using AIS info in conjunction with our boats radar and MARPA functionality. MARPA is an acronym for Mini Automatic Radar Plotting Aid. The primary purpose of MARPA is Collision Avoidance and target tracking. AIS and MARPA targets are displayed in the same fashion. There is no way to manually correlate the AIS/MARPA targets on the chart plotter. What you end up with is a very cluttered display.
Of the sixteen AIS vessels we tracked none displayed a name in appropriate field. The only thing we saw in regards to vessel ID were international call signs. CPA data was good when available however it would disappear when our equipment lost communication with the target vessels transponder. After one minute the AIS ship icon would disappear from our chart plotter. When AIS communication was re-established then the data and ship icon would return. It was about 50/50 in the data exchange world.
Going out this weekend so I'll take some video.
Tom
towboater posted 01-14-2009 01:52 PM ET (US)
I called the local Marine Electronics Tech in Portland yesterday, they are anxiously waiting for the Icom AIS receiver...so am I.
Their current AIS receiver also requires a 4 ft whip antenna.
I asked about the receiving range of current AIS recievers, Marty said it depends on whether or not the transmitted AIS signal from the vessel is received by a re-transmitter. On the Columbia, there is a re-transmitter approx 45 miles inland (my area). I will be able to follow ships progress from the Ocean all the way to Portland. Otherwise, he said reception would vary substantially...according to line of sight.
$450 is much lower than Marty quoted and I wouldn't mind paying a little extra to Marty if he had one...I may be ordering one from you soon Tom. Thanks.
Michael K
jimh posted 01-14-2009 08:13 PM ET (US)
Michael--Please let me know the call sign of the station that is licensed to act as a repeater for AIS transmissions. I have never heard of this before. I had no idea that the FCC was licensing transmitters to act as repeaters for the AIS channels. Your mention is the first I have heard of it, but I would really like to know more about it. Give us the callsign of the station acting as a repeater, and I can look up the details of their license on the FCC database to see how they do it.
jimh posted 01-15-2009 12:01 AM ET (US)
The AIS channel is at the high end of the normal VHF Marine Band. Propagation at those frequencies is the same as for other VHF Marine Band signals. The power of the AIS transponders is lower than most VHF Marine band transmitters. I believe that a Class-B transponder transmits at 2-watts, and a Class-A transponders can run 12.5-watts. The anticipated range will primarily depend on the height of the antenna. A typical range between two ships that had their antennas mounted 50-feet above the water would be 20-miles.
bluewaterpirate posted 01-15-2009 08:31 AM ET (US)
Bingo, small boat reception footprint is the issue.
jimh posted 01-15-2009 09:25 AM ET (US)
To clarify the receiver capabilities, the ICOM's product literature now says:
"Dual channel receive capability
"The MXA-5000 receives both Ch. 87B (161.975MHz) and Ch. 88B (162.025MHz) simultaneously. This dual channel receive makes the MXA-5000 more flexible for obtaining AIS information from AIS transponders that operate on only one channel. In addition, the MXA-5000 also receives both Class A and Class B AIS data."
As for the price, if you can find the MXA-5000 for $450 that is a decent price when compared to other dual channel receivers. The Milltech SR 162 is still selling for $399 but lacks the antenna splitter.The Comar AIS-2 dual receiver is $369, but, again, it also lacks the antenna splitter provided in the ICOM.
I guess in dual receiver AIS products, the ICOM is currently about the best value if you are planning on using the same antenna for your AIS as for your VHF Marine Band radio. On a small recreational boat, sharing the same antenna for your VHF Marine Band radio and your AIS receiver is going to be a common siutation. Most small boats don't have room for dual antennas. The ICOM brand name is also much more familiar to most boaters, and that makes it more attractive than some alternatives that might be a slightly cheaper.
towboater posted 01-15-2009 11:26 AM ET (US)
Marty (Rogers Marine Electronics, Portland) was equally curious about the repeater factor Jim. Id bet the two of you could talk "shop" for hours. He said the AIS receiver demo in his store in Portland Harbor picks up ships out in the Ocean (120 miles away).
He concluded and I agree the most likely candidate to "need" a AIS repeater is the Columbia River Pilots since the river twists and turns between fairly high mountains.
http://www.colrip.com/default.asp
I dont have time to find out for sure today.
mk
jimh posted 01-16-2009 02:28 PM ET (US)
I have looked into the topic of AIS signals being retransmitted. I tend to doubt that the signals from one vessel are actually retransmitted by a shore station. However, the automatic identification system includes a category for AIS BASE STATION, as follows:
AIS base station
Shore-based station providing text messages, time synchronization, meteorological or hydrological information, navigation information, or position of other vessels. Normally reports every ten seconds.
Cf.: http://www.navcen.uscg.gov/enav/ais/types_of_AIS.htm
From that description I infer that an AIS base station may receive signals from a vessel's AIS transponder which includes the vessel's position. The AIS base station then may include that data in its transmissions, but it does not actually retransmit or repeat the radio signal from the vessel. The AIS base station extracts the data from the vessel's AIS transmission, and then includes the data in the AIS base station's signal.
jimh posted 01-17-2009 10:21 AM ET (US)
It just came to my attention (thanks to an article on PANBO.COM) that the RAYMARINE AIS250 receiver is not capable of simultaneous reception on both AIS channels. Now here comes the ICOM MXA5000 with a unit that can simultaneously receive both AIS channels, and with a price that is about half of the Raymarine unit. I'd say that this really makes the ICOM MXA5000 AIS receiver the front runner on both price and performance among the major brand name units.
towboater posted 01-26-2009 04:57 AM ET (US)
Jim
Columbia River AIS repeaters are property of Columbia River Pilots. Dont ask me how it works...
I got this info from brief conversation with Foss Towboat Dispatcher.
Bottom line, there are AIS repeaters.
mk
jimh posted 01-26-2009 08:30 AM ET (US)
MK--Just ask the fellow for the FCC call sign of the shore station that acts as a repeater.
towboater posted 01-29-2009 04:14 AM ET (US)
Whats the deal Jim? Columbia River Pilots have a friggin AIS repeater, do you think Im full of BS?
I gave you a link to the Pilots website, call Dispatch...tell em Mike Johnson referred you. Then they will ask you which Mike Johnson? Tell them Michael K, they might laugh or might say oh god...but, they will do their best to answer your AIS repeater questions.
mk
jimh posted 01-29-2009 08:08 AM ET (US)
Yes, I think your description is wrong. I have never heard of any repeaters authorized in the VHF Marine Band. It would be technically difficult for a repeater to be built which transmitted on the same frequency as it listened. Perhaps you can explain how that works. Normally, if a repeater transmits on the same frequency as it is listening, the result is a feedback loop. But I am open to explanations of how the pilots of the Pacific Northwest have figured out how to avoid that problem.
I'll try to reach them to discover what facility they have. Thanks.

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Author	Topic: ICOM AIS Receiver
jimh	posted 01-05-2009 08:10 PM ET (US) ICOM have announced the MXA5000 AIS Receiver. Details are limited to those contained in the press release: http://www.icomamerica.com/en/media_events/news/NewsArticle. aspx?id=200809 ICOM's release refers to the MXA5000 as a "Class B Receiver" but this designation makes no sense. In the automatic identification service both Class-A and Class-B transponders use mostly the same protocols and transmit on the same frequencies. ICOM also refers to the device as having a "full duplex" receiver, which I interpret to mean that it receives simultaneously on both AIS channels. The MSRP is anticipated to be about $500. The MXA5000 contains an antenna switch which permits the vessel's existing VHF Marine Band radio antenna to be used as a receive antenna for the AIS receiver. Outboard devices that provide this function can cost as much as $250. This mitigates the cost of the MXA5000 somewhat. Considering the built-in multiplexer and the dual-receive capability, the ICOM's price of $500 is not excessive, particularly when compared to some other brand name receive-only devices which have been offered at $800. The MXA5000 AIS receiver should be available in a few months.
towboater	posted 01-06-2009 01:25 AM ET (US) Quote from the Icom promo... "AIS is used by ships and Vessel Traffic Services for identification and locating vessels." Why would someone need AIS on a recreational Boston Whaler? For whatever good reason a BW owner may have, my fear is that AIS may lull a Recreational Boater into a false sense of security. Beware, there are still many large vessels that are not required to transmit AIS signals you should constantly watch out for. Otherwise, the Icom looks like a nice setup. Thx Jim. mk
Chuck Tribolet	posted 01-06-2009 08:05 AM ET (US) We're going to see AIS receivers built into VHF raadios. It can be done for < $25 mfg cost, perhaps a lot less. Chuck
jimh	posted 01-06-2009 08:18 AM ET (US) Why would someone need an AIS receiver on a Boston Whaler? For the same type of reason that someone needs a $4,000 color display, precision fix GPS receiver, and digital side scan SONAR. It's another electronic gizmo. You don't need any of them, but that seldom stops people from having them. Regarding the price of an AIS receiver, the cheapest is still about $200. I have a listing at http://continuouswave.com/whaler/reference/AIS.html
jimh	posted 01-06-2009 08:35 AM ET (US) Chuck--Given the costs of shipping, marketing, distribution, sales, and so on, it may very well be that a device selling for around $500 has an actual manufacturing cost of about $25. As for incorporating an AIS receiver into a VHF Marine Band Radio, it is possible, but it is not as trivial as you might think. Let's look at what is already in a VHF Marine Band radio: --25-watt FM transmitter, frequency agile --FM receiver, voice modulation, frequency agile --DSC receiver, data modem, dedicated to DSC channel --DSC control system compliant with Class-D specification --NMEA serial data interface, input and output In an AIS receiver we would add: --AIS receiver, data modem, first channel --AIS receiver, data modem, second channel --serial data interface The radio would have four receivers, all capable of simultaneous and independent reception, as long as the transmitter was not operating. Providing four receive channels will take some careful engineering. They're all connected to the same antenna, and there is the possibility of some mutual interference. It's not impossible to do, but it will take careful design. At the moment I would guess that some of the cost represents licensing of some fundamental software or processing from a third party. Not all the manufacturers may have taken the time to engineer and develop all the details of AIS reception themselves. One firm in the U.K. seems to be a leader in AIS development.
Chuck Tribolet	posted 01-06-2009 12:39 PM ET (US) It's entirely possible that they are using software receivers now, so the four "receivers" would share a single wide-band A-D converter. No interferance problems. In any event, they've already solved the interferance problems for two receivers. Chuck
bluewaterpirate	posted 01-06-2009 10:41 PM ET (US) Here's some more data on the unit http://www.icomamerica.com/en/products/marine/navigation/mxa5000/ default.aspx
bluewaterpirate	posted 01-06-2009 10:51 PM ET (US) You can place your order. http://www.docksideradio.com/AIS%20MXA-5000.htm
jimh	posted 01-07-2009 09:02 AM ET (US) Hey--the price went up $100 already! (The unit is advertised at $600; the press release mentioned $500.)
towboater	posted 01-10-2009 11:03 AM ET (US) On why a recreational boater would need AIS as a navigational tool (beyond a luxury toy), it has occurred to me... AIS info could be very helpful to separate known and unknown targets in a congested area. For example; You are anchored or running near the edge of a congested navigable channel in deep water. One ship or Towboat may be overtaking another headed in your direction but still too far away to see the names. AIS would confirm who is who and you would quickly understand the passing situation without needing to ask. mk
jimh	posted 01-10-2009 11:17 AM ET (US) I just noticed that you can purchase an ACR Nauticast-B AIS Class-B Transponder system from various resellers for about $750. This includes: --AIS dual channel receiver --AIS Class-B transponder (2-watt) --GPS receiver --GPS receiver antenna --AIS transmit-receiver antenna --NMEA dual serial ports This is a FCC certified Class-B transponder which will transmit your vessel identity to others, as well as a dual channel receiver, and a GPS receiver. It also includes two antennas! The price of the ICOM receive-only AIS product seems a bit excessive in comparison. Cf.: http://store.milltechmarine.com/acraisproducts.html
Olsonist	posted 01-13-2009 12:10 PM ET (US) At $500 (or less) and with a built-in splitter [the ICOM AIS MXA5000] is 60% less than the NAIS-300-L Class B AIS Transponder and splitter at about $1,300. Lower power, smaller footprint, better integration. What's not to like? Well, NMEA 2000 would have been nice. It might still be.
bluewaterpirate	posted 01-13-2009 12:21 PM ET (US) [The ICOM MXA5000] is selling for $450. Better overview of connectivity. http://albums.phanfare.com/4892322/2160052#imageID=57961608
jimh	posted 01-13-2009 08:00 PM ET (US) The ICOM MXA5000 is just a receiver; it is not a transponder. It ought to cost a lot less than a certified Class-B transponder.
jimh	posted 01-13-2009 08:04 PM ET (US) It is not clear if there is any AIS receiver that has a NMEA-2000 interface. The RAYMARINE AIS500 transponder may have a NMEA-2000 interface. It is noted as having a SeaTalkNG interface, which is Raymarine's name for NMEA-2000. See: http://www.jgtech.com/shop10.htm
bluewaterpirate	posted 01-13-2009 11:47 PM ET (US) Spent four hours on the water last weekend using two different AIS systems. The biggest problem was the periodic loss of data from vessels in our immediate area. The other issue was using AIS info in conjunction with our boats radar and MARPA functionality. MARPA is an acronym for Mini Automatic Radar Plotting Aid. The primary purpose of MARPA is Collision Avoidance and target tracking. AIS and MARPA targets are displayed in the same fashion. There is no way to manually correlate the AIS/MARPA targets on the chart plotter. What you end up with is a very cluttered display. Of the sixteen AIS vessels we tracked none displayed a name in appropriate field. The only thing we saw in regards to vessel ID were international call signs. CPA data was good when available however it would disappear when our equipment lost communication with the target vessels transponder. After one minute the AIS ship icon would disappear from our chart plotter. When AIS communication was re-established then the data and ship icon would return. It was about 50/50 in the data exchange world. Going out this weekend so I'll take some video. Tom
towboater	posted 01-14-2009 01:52 PM ET (US) I called the local Marine Electronics Tech in Portland yesterday, they are anxiously waiting for the Icom AIS receiver...so am I. Their current AIS receiver also requires a 4 ft whip antenna. I asked about the receiving range of current AIS recievers, Marty said it depends on whether or not the transmitted AIS signal from the vessel is received by a re-transmitter. On the Columbia, there is a re-transmitter approx 45 miles inland (my area). I will be able to follow ships progress from the Ocean all the way to Portland. Otherwise, he said reception would vary substantially...according to line of sight. $450 is much lower than Marty quoted and I wouldn't mind paying a little extra to Marty if he had one...I may be ordering one from you soon Tom. Thanks. Michael K
jimh	posted 01-14-2009 08:13 PM ET (US) Michael--Please let me know the call sign of the station that is licensed to act as a repeater for AIS transmissions. I have never heard of this before. I had no idea that the FCC was licensing transmitters to act as repeaters for the AIS channels. Your mention is the first I have heard of it, but I would really like to know more about it. Give us the callsign of the station acting as a repeater, and I can look up the details of their license on the FCC database to see how they do it.
jimh	posted 01-15-2009 12:01 AM ET (US) The AIS channel is at the high end of the normal VHF Marine Band. Propagation at those frequencies is the same as for other VHF Marine Band signals. The power of the AIS transponders is lower than most VHF Marine band transmitters. I believe that a Class-B transponder transmits at 2-watts, and a Class-A transponders can run 12.5-watts. The anticipated range will primarily depend on the height of the antenna. A typical range between two ships that had their antennas mounted 50-feet above the water would be 20-miles.
bluewaterpirate	posted 01-15-2009 08:31 AM ET (US) Bingo, small boat reception footprint is the issue.
jimh	posted 01-15-2009 09:25 AM ET (US) To clarify the receiver capabilities, the ICOM's product literature now says: "Dual channel receive capability "The MXA-5000 receives both Ch. 87B (161.975MHz) and Ch. 88B (162.025MHz) simultaneously. This dual channel receive makes the MXA-5000 more flexible for obtaining AIS information from AIS transponders that operate on only one channel. In addition, the MXA-5000 also receives both Class A and Class B AIS data." As for the price, if you can find the MXA-5000 for $450 that is a decent price when compared to other dual channel receivers. The Milltech SR 162 is still selling for $399 but lacks the antenna splitter.The Comar AIS-2 dual receiver is $369, but, again, it also lacks the antenna splitter provided in the ICOM. I guess in dual receiver AIS products, the ICOM is currently about the best value if you are planning on using the same antenna for your AIS as for your VHF Marine Band radio. On a small recreational boat, sharing the same antenna for your VHF Marine Band radio and your AIS receiver is going to be a common siutation. Most small boats don't have room for dual antennas. The ICOM brand name is also much more familiar to most boaters, and that makes it more attractive than some alternatives that might be a slightly cheaper.
towboater	posted 01-15-2009 11:26 AM ET (US) Marty (Rogers Marine Electronics, Portland) was equally curious about the repeater factor Jim. Id bet the two of you could talk "shop" for hours. He said the AIS receiver demo in his store in Portland Harbor picks up ships out in the Ocean (120 miles away). He concluded and I agree the most likely candidate to "need" a AIS repeater is the Columbia River Pilots since the river twists and turns between fairly high mountains. http://www.colrip.com/default.asp I dont have time to find out for sure today. mk
jimh	posted 01-16-2009 02:28 PM ET (US) I have looked into the topic of AIS signals being retransmitted. I tend to doubt that the signals from one vessel are actually retransmitted by a shore station. However, the automatic identification system includes a category for AIS BASE STATION, as follows: AIS base station Shore-based station providing text messages, time synchronization, meteorological or hydrological information, navigation information, or position of other vessels. Normally reports every ten seconds. Cf.: http://www.navcen.uscg.gov/enav/ais/types_of_AIS.htm From that description I infer that an AIS base station may receive signals from a vessel's AIS transponder which includes the vessel's position. The AIS base station then may include that data in its transmissions, but it does not actually retransmit or repeat the radio signal from the vessel. The AIS base station extracts the data from the vessel's AIS transmission, and then includes the data in the AIS base station's signal.
jimh	posted 01-17-2009 10:21 AM ET (US) It just came to my attention (thanks to an article on PANBO.COM) that the RAYMARINE AIS250 receiver is not capable of simultaneous reception on both AIS channels. Now here comes the ICOM MXA5000 with a unit that can simultaneously receive both AIS channels, and with a price that is about half of the Raymarine unit. I'd say that this really makes the ICOM MXA5000 AIS receiver the front runner on both price and performance among the major brand name units.
towboater	posted 01-26-2009 04:57 AM ET (US) Jim Columbia River AIS repeaters are property of Columbia River Pilots. Dont ask me how it works... I got this info from brief conversation with Foss Towboat Dispatcher. Bottom line, there are AIS repeaters. mk
jimh	posted 01-26-2009 08:30 AM ET (US) MK--Just ask the fellow for the FCC call sign of the shore station that acts as a repeater.
towboater	posted 01-29-2009 04:14 AM ET (US) Whats the deal Jim? Columbia River Pilots have a friggin AIS repeater, do you think Im full of BS? I gave you a link to the Pilots website, call Dispatch...tell em Mike Johnson referred you. Then they will ask you which Mike Johnson? Tell them Michael K, they might laugh or might say oh god...but, they will do their best to answer your AIS repeater questions. mk
jimh	posted 01-29-2009 08:08 AM ET (US) Yes, I think your description is wrong. I have never heard of any repeaters authorized in the VHF Marine Band. It would be technically difficult for a repeater to be built which transmitted on the same frequency as it listened. Perhaps you can explain how that works. Normally, if a repeater transmits on the same frequency as it is listening, the result is a feedback loop. But I am open to explanations of how the pilots of the Pacific Northwest have figured out how to avoid that problem. I'll try to reach them to discover what facility they have. Thanks.