AIS/VHF two antennae's or one?

[stephen_i_w]

It is not, and I explained why. It is similar to why calling the Coast Guard is not a good way to test the quality of your VHF transmission. You even elude to this when you mention how easy it is for the CG and Marine Traffic to see you with large radio towers.

Seeing a mast is not a good way to avoid a collision coming in a blind breakway or inlet. There is no easy way to tell direction, or timing. Then there are boats like tugs and barges that can't be seen at all. If you haven't seen visually obstructed breakwaters or inlets, then you've had it easy. Right now, I'm at the mouth of the Panama Canal, where there the breakwater is tall enough to hide container ships, and avoiding the ships while coming in the breakwater is a blind game of frogger. AIS makes this a piece of cake, but it is tough visually, and is mostly guessing, hoping, and reacting quickly at the last minute without it.

I've never questioned having an AIS transponder. Quite the opposite - I'd like to see every boat have one.

I agree that running a second antenna COULD be less expensive than a splitter, and it was in your case, but it isn't necessarily so. It would cost more than a splitter on our boat, for example. I was just pointing this out, because being less expensive than a splitter is not universally true.

Rail mount works fine for what it is. There just isn't any argument that lower height is better, or that one only cares about other slow boats a mile or so away, and not anything at larger distances. As someone who regularly sails short handed in large sea states, with strong winds, at night or in poor visibility, often with sails prevented, I am grateful to have notice of an unseen boat 10nm away so that I have time to chose my option, prepare the boat, and safely make a course change if needed. I appreciate when my signal gets out 10nm or more and the other ship has an equal opportunity. Detection distance isn't as critical in calmer conditions and good visibility.

Yes, power boaters have height constraints and still manage (although they get a bit of help with higher-gain antennas). So do kayakers with handheld radios. I don't see how this matters, as each is using their best option. It would be like telling a power boater that putting his antenna in the cabin below is just as good as above on the rail.

Mark

You have to account for different needs on the water. I sail in the Great Lakes. Very few of us sail in places like the Panama Canal. I will grant you that for blue water sailors things are different. But, come on now, most of us, almost all of us in fact, sail in coastal or inland areas. Here, my argument is valid. As for seeing tugs or barges, we are talking about our own visibility, not the visibility of other vessels. But in any case, as commercial vessels, tugs and barges are all quite visible over long distances on AIS. They even use a higher-power version of AIS than recreational vessels (Class A). I know this, because I see them all the time on my chart plotter 10 and 20 nm away. I live in a high marine traffic area.

Boats have an infinite capacity to absorb dollars and time. Not all of us has an infinite supply of either. What I am suggesting is more than adequate for the overwhelming majority of sailors. AIS is not a substitute for a sailor's eyes or good judgment.

 

[BAD ORCA]

OK, so that is much clearer now. You have a receive-only AIS in your VHF that naturally uses the same antenna. No splitting is required because there is no AIS transmission that needs splitting.

A stand alone AIS transponder is an excellent idea. For this, you will make decisions discussed in this thread as to its installation and antenna hows and wheres.

LMR400 is a beast of cable. Make sure your mast has the conduit room for two runs of it, along with other wires needed up there for the usual stuff.

It doesn't sound like Capta understood his AIS system. The alarms can be highly customized as to distance, speed, time, etc, and can be turned off completely. Turning the alarms off does not immediately make all boats zoom toward you at high speed. None of this is any different than the identical functions on a modern ARPA radar. For sure, eyeballs and good binoculars are important, but they are pretty useless in the conditions where AIS is invaluable, like heavy fog or rain, or targets visually blocked by land or other boats. And plotting out and calculating positions over many minutes while bouncing around in the middle of the night is more fraught with potential error than a quick glance at a target on AIS telling you that you will pass its stern by 0.5nm in 26min.

Mark

HA! Yeah plus in mast halyards. Im going to run a dyneema mouse wire but dont think i'm pulling any LMR400 through with a mouse wire. Definitely want to get that through first.

 

[BAD ORCA]

You have to account for different needs on the water. I sail in the Great Lakes. Very few of us sail in places like the Panama Canal. I will grant you that for blue water sailors things are different. But, come on now, most of us, almost all of us in fact, sail in coastal or inland areas. Here, my argument is valid. As for seeing tugs or barges, we are talking about our own visibility, not the visibility of other vessels. But in any case, as commercial vessels, tugs and barges are all quite visible over long distances on AIS. They even use a higher-power version of AIS than recreational vessels (Class A). I know this, because I see them all the time on my chart plotter 10 and 20 nm away. I live in a high marine traffic area.

Boats have an infinite capacity to absorb dollars and time. Not all of us has an infinite supply of either. What I am suggesting is more than adequate for the overwhelming majority of sailors. AIS is not a substitute for a sailor's eyes or good judgment.

I think we can all agree on this but i'm interested in long distance blue water sailing to some pretty remote places. If someone else is interested in local bay sailing, they need to make these determinations for themselves and ask their own questions. Your points are valid though and thanks for sharing for any future readers of this thread.

 

[Captain Larry-DH]

Also, as CAPTA mentions nuisance signals. If its a standalone transponder, I'm guessing it would be as easy as flicking a breaker to turn it off if i'm just day sailing in the local bay.

Just turn off the proximity alarm setting. You can find the setting in the VHF radio's manual.
Also - You don't benefit from the "be seen" function of AIS if it's off. I'm with Mark on this issue - I wish all boaters has AIS transceivers on all the time. The only benefit to not transmitting is to people trying to keep a low profile in parts of the world where pirates are a concern.

 

[colemj]

Even for the Chesapeake, and definitely in the ICW, there are a lot of blind turns and entrances. And a lot of fog, rain, and other low visibility situations. Not to mention a lot of commercial traffic.

The reason commercial traffic is visible longer range is because their antennas are usually mounted high and they use more power like you said. It also behooves recreational sailors to optimize the distance they can be seen for the same reasons. As a simile, one doesn't turn down the volume on their fog horn so that are only heard by boats that are close to them and not those further out.

Sure, I get that we are sailing in more challenging conditions and areas. All I was trying to get through in my posts is there are compromises to be made, and what those compromises are - and understanding these is important. Antenna height is one of them, as is splitter/no splitter, type of coax, etc. Very few of us are in a position to optimize all aspects, so choices need to be made depending on individual circumstances.

Mark

 

[BAD ORCA]

Just turn off the proximity alarm setting. You can find the setting in the VHF radio's manual.
Also - You don't benefit from the "be seen" function of AIS if it's off. I'm with Mark on this issue - I wish all boaters has AIS transceivers on all the time. The only benefit to not transmitting is to people trying to keep a low profile in parts of the world where pirates are a concern.

that might be a future consideration when trying to get to Patagonia.

 

[east coaster]

On my Catalina 2002 310 I have an Emtrak system that works fine with one antenna. It also is on wifi so I can get the ais info on any other device. It's the same system as AndyBC I would wager.

 

[Hello Below]

I wish all boaters has AIS transceivers on all the time.

I wish all boaters would disable their AIS transponder when alongside.

If you own a Raymarine MFD that runs Lighthouse 4.6.74 or older you will be limited to the closest (CPA) 100 targets. On a recent passage I was within 2 NM of a large passenger ferry doing 19 kts coming straight for me. Mark 1 eye ball and ARPA confirmed that I needed to make a course adjustment quickly. When in safe waters, I determined the number of targets tracked by my Raymarine eSeries to be 100 at 1.6 NM or less. Once the ferry got within 1.5 miles it showed up as an AIS target but not before. As of February 2024 LH version 4.6.74 increased the buffer to 200 targets which may or may not help. Ideally the user should be able to filter the targets by CPA, distance, speed or a combination of those. Not by distance alone. FWIW I counted approximately 240 targets being received using the USB o/p from my Vesper splitter and ProAIS2. Over 80% of the targets had a speed of 0 kts and were thus tied up alongside or at least of little concern.

 

[dLj]

I wish all boaters would disable their AIS transponder when alongside.

If you own a Raymarine MFD that runs Lighthouse 4.6.74 or older you will be limited to the closest (CPA) 100 targets. On a recent passage I was within 2 NM of a large passenger ferry doing 19 kts coming straight for me. Mark 1 eye ball and ARPA confirmed that I needed to make a course adjustment quickly. When in safe waters, I determined the number of targets tracked by my Raymarine eSeries to be 100 at 1.6 NM or less. Once the ferry got within 1.5 miles it showed up as an AIS target but not before. As of February 2024 LH version 4.6.74 increased the buffer to 200 targets which may or may not help. Ideally the user should be able to filter the targets by CPA, distance, speed or a combination of those. Not by distance alone. FWIW I counted approximately 240 targets being received using the USB o/p from my Vesper splitter and ProAIS2. Over 80% of the targets had a speed of 0 kts and were thus tied up alongside or at least of little concern.

I'm with Captain Larry on this one and would prefer to have all boats have their AIS turned on - and that all boats would have one, especially in congested waters. But my AIS transponder does not have a limitation of how many boats it displays. Another good point is knowing what the limitations of your equipment actually is. Which brings me to another point of why I don't care for multifunctional pieces of equipment - I prefer standalone units that do what they do best. If that one multifunctional piece of electronics goes down, I've now lost all the functions it was providing. Whereas, with standalone units, if one goes down, I still have my other units.

I set my AIS to alarm if there is a calculated POA (point of approach) to be below a defined threshold. Depending upon where I am, I set that at different distances typically ranging from 2 nm to 0.5 nm. Doing it this way, the ferry in the above example would have given me an alarm when that ferry was about 26 NM away, or when it came close enough for my AIS to detect it - typically about that distance. I'd then have it earmarked for monitoring from quite a long distance away. No surprises at close range.

Just my 2 cents...

dj

 

[Hello Below]

I can only speak for Raymarine users with Lighthouse software pre-Feb 2024. Unfortunately for those users hiding the targets using CPA (Closest Point of Approach), speed or distance does not help. Doing this only hides those targets on the chartplotter but they still appear in the AIS targets list and continue to be counted toward the 100-target limit. In my example if I set a speed filter of say 1 kt I would see approx 20 targets on my chartplotter but not the ferry barrelling down on me. It have been target #148.

Edit: With my LightHouse version I can only set time and distance to define a Dangersous Target. I cannot set a speed filter.

 

[dLj]

I can only speak for Raymarine users with Lighthouse software pre-Feb 2024. Unfortunately for those users hiding the targets using CPA (Closest Point of Approach), speed or distance does not help. Doing this only hides those targets on the chartplotter but they still appear in the AIS targets list and continue to be counted toward the 100-target limit. In my example if I set a speed filter of say 1 kt I would see approx 20 targets on my chartplotter but not the ferry barrelling down on me. It have been target #148.

Ah right, CPA, I never remember these correctly, thanks for putting the right one up.

Also, for sure anyone running the same software as you should be made aware of this.

I don't understand your speed filter? Does that mean all boats traveling less than 1 kt are not displayed? How does it relate to CPA? Does this mean in your software, even filtering such that there are fewer targets, It won't alarm for targets that might trip the CPA alarm if they are say boat #148 in that program? Dang! That's a serious problem!!!

dj

p.s. I'm not filtering on CPA - only alarming... I typically don't filter at all.

 

[Captain Larry-DH]

I wish all boaters would disable their AIS transponder when alongside.

If you own a Raymarine MFD that runs Lighthouse 4.6.74 or older you will be limited to the closest (CPA) 100 targets. On a recent passage I was within 2 NM of a large passenger ferry doing 19 kts coming straight for me. Mark 1 eye ball and ARPA confirmed that I needed to make a course adjustment quickly. When in safe waters, I determined the number of targets tracked by my Raymarine eSeries to be 100 at 1.6 NM or less. Once the ferry got within 1.5 miles it showed up as an AIS target but not before. As of February 2024 LH version 4.6.74 increased the buffer to 200 targets which may or may not help. Ideally the user should be able to filter the targets by CPA, distance, speed or a combination of those. Not by distance alone. FWIW I counted approximately 240 targets being received using the USB o/p from my Vesper splitter and ProAIS2. Over 80% of the targets had a speed of 0 kts and were thus tied up alongside or at least of little concern.

I just don't see how this is a problem. The tools are there to focus on what's important to you, just as with Mark 1 eyeball.
You can disable display of stationary targets. You can also display them in order of CPA. You can also overlay them on your chart and see only those in view, with appropriate filters applied. In a dense harbor with lots of converging traffic I'm generally not at all concerned with anything beyond about 1/4-1 NM. I've drifted/anchored in the general ship anchorage south of the NY Battery with freighters, tugs and barges and the SI Ferry crossing in every direction and never had any issue while waiting for the East River current change.
I'm curious what screen displays you used and where this was an issue, as I've been up and down the entire East Coast US a few times and it was never a problem for me even on the busiest harbors. (e.g. Ft Lauderdale, Miami, Charleston, Norfolk, Annapolis, Baltimore, NYC, Newport, Boston etc.)
(PS - I update my CP at every opportunity.)

 

[Captain Larry-DH]

p.s. I'm not filtering on CPA - only alarming... I typically don't filter at all.

I don't alarm on anything. It would drive me crazy and I'd just be ignoring them, unless we were out in an open sea area. I just keep watch

 

[dLj]

I don't alarm on anything. It would drive me crazy and I'd just be ignoring them, unless we were out in an open sea area. I just keep watch

I set the alarm when I'm out of the harbor or sailing at night. When running in highly congested, especially when running in shipping channels with ships all around I may turn it off. As you say, it depends upon how much of the time it's going off. Sailing through the shipping channels of Gibraltar I just turned it off - there were way too many boats and it was just a nuisance. But most of the time it was very useful.

dj

 

[colemj]

I wish all boaters would disable their AIS transponder when alongside.

If you own a Raymarine MFD that runs Lighthouse 4.6.74 or older you will be limited to the closest (CPA) 100 targets. On a recent passage I was within 2 NM of a large passenger ferry doing 19 kts coming straight for me. Mark 1 eye ball and ARPA confirmed that I needed to make a course adjustment quickly. When in safe waters, I determined the number of targets tracked by my Raymarine eSeries to be 100 at 1.6 NM or less. Once the ferry got within 1.5 miles it showed up as an AIS target but not before. As of February 2024 LH version 4.6.74 increased the buffer to 200 targets which may or may not help. Ideally the user should be able to filter the targets by CPA, distance, speed or a combination of those. Not by distance alone. FWIW I counted approximately 240 targets being received using the USB o/p from my Vesper splitter and ProAIS2. Over 80% of the targets had a speed of 0 kts and were thus tied up alongside or at least of little concern.

This sounds like a Raymarine problem, or at least a problem of choice. It would be silly for everyone to disable their AIS transmissions just because one particular piece of equipment can't handle it, while all others can.

AIS has been around for a long time, which spans many generations of software development for those devices incorporating it. It has become universal, and several countries even require it on all boats and to be on at all times, so there really is no excuse for not handling it well today.

We have 6 separate and different non-Raymarine devices encompassing plotters, apps, programs, and standalone units from different manufacturers, and all of them handle this easily. They all also have an "ignore stationary vessels" setting too, along with complete customization of what to display, alarm, and ignore. The Furuno plotter on our previous boat handled this with ease, and that was 5 generations and 14yrs in the past.

Mark

 

[colemj]

I don't alarm on anything. It would drive me crazy and I'd just be ignoring them, unless we were out in an open sea area. I just keep watch

We don't have alarms set also for the same reason. Most of our devices that display AIS have settings to allow target COG lines to be extended for a user-adjustable length based on either time or distance. We just have those set for 30min, and it is easy to see if/when any of these lines appear in your immediate area.

Mark

 

[Hello Below]

This sounds like a Raymarine problem, or at least a problem of choice. It would be silly for everyone to disable their AIS transmissions just because one particular piece of equipment can't handle it, while all others can.

AIS has been around for a long time, which spans many generations of software development for those devices incorporating it. It has become universal, and several countries even require it on all boats and to be on at all times, so there really is no excuse for not handling it well today.

We have 6 separate and different non-Raymarine devices encompassing plotters, apps, programs, and standalone units from different manufacturers, and all of them handle this easily. They all also have an "ignore stationary vessels" setting too, along with complete customization of what to display, alarm, and ignore. The Furuno plotter on our previous boat handled this with ease, and that was 5 generations and 14yrs in the past.

Mark

This is definitely a Raymarine problem, I spent the best part of an hour talking to the leads for Raymarine sales, software and engineering at the 2023 Annapolis boat show. In short I told them that limiting the number of targets to 100 was a show stopper for me buying a Raymarine MFD. They admitted they were working on a fix and a new LightHouse update in Jan (2024) would increase the target limit to 200. That did happen in Feb this year. Obviously 200 is better than 100 but not the answer.
With the older Lighthouse software (pre-2024???), users can choose to display only Dangerous AIS Targets with both the time and distance settable. All that does however is reduce the clutter outside of your settable safe distance and time parameters. And since the 2024 LH software release, speeds under 2kts can also be hid from the display. However, in both cases that does not increase the allowable number of vessels in the target list. That is 100 for me and 200 for the newer version.
An example of a problem was as above. A high speed target (ferry) doing 19 kts out of view behind an island was not in the target list thus not displayed on the screen. When it finally became target number 100 (or less) it popped up on the display at about 1.5 Nm and less than 4 minute time to CPA (TCPA). Stressful.
Another area where I have exceeded 100 targets was around Anacortes. Two large marinas within 2 Nm overwhelmed the 100 count AIS target list. A Washington state ferry was closing at a distance of 2.5 Nm but did not show up on my display until it closed to 1.6 Nm obviously now number 100 target or less. Fortunately this ferry was visual and caused little stress.
In closing, until a release of LightHouse software limits the target list by distance rather than a finite number and allows the user to choose the time, distance, speed settings to display targets then I would not consider purchasing a Raymarine chartplotter.

PS - I updated my CP at every opportunity also. However like iPhones age catches up and updates are no longer offered.
PSS - Although I disable the audible alarm, the screen does display a flashing red vessel icon if it is in the dangerous target area.

 

[dLj]

This is definitely a Raymarine problem, I spent the best part of an hour talking to the leads for Raymarine sales, software and engineering at the 2023 Annapolis boat show. In short I told them that limiting the number of targets to 100 was a show stopper for me buying a Raymarine MFD. They admitted they were working on a fix and a new LightHouse update in Jan (2024) would increase the target limit to 200. That did happen in Feb this year. Obviously 200 is better than 100 but not the answer.
With the older Lighthouse software (pre-2024???), users can choose to display only Dangerous AIS Targets with both the time and distance settable. All that does however is reduce the clutter outside of your settable safe distance and time parameters. And since the 2024 LH software release, speeds under 2kts can also be hid from the display. However, in both cases that does not increase the allowable number of vessels in the target list. That is 100 for me and 200 for the newer version.
An example of a problem was as above. A high speed target (ferry) doing 19 kts out of view behind an island was not in the target list thus not displayed on the screen. When it finally became target number 100 (or less) it popped up on the display at about 1.5 Nm and less than 4 minute time to CPA (TCPA). Stressful.
Another area where I have exceeded 100 targets was around Anacortes. Two large marinas within 2 Nm overwhelmed the 100 count AIS target list. A Washington state ferry was closing at a distance of 2.5 Nm but did not show up on my display until it closed to 1.6 Nm obviously now number 100 target or less. Fortunately this ferry was visual and caused little stress.
In closing, until a release of LightHouse software limits the target list by distance rather than a finite number and allows the user to choose the time, distance, speed settings to display targets then I would not consider purchasing a Raymarine chartplotter.

PS - I updated my CP at every opportunity also. However like iPhones age catches up and updates are no longer offered.
PSS - Although I disable the audible alarm, the screen does display a flashing red vessel icon if it is in the dangerous target area.

I had heard about this kind of limitation a while back, not as clearly as you have explained. So I checked several times with my AIS to see if I had a similar limitation. I have not found one - thankfully. But this is clearly something that folks need to be aware of and I thank you for bringing it up.

dj

 

[Hello Below]

I had heard about this kind of limitation a while back, not as clearly as you have explained. So I checked several times with my AIS to see if I had a similar limitation. I have not found one - thankfully. But this is clearly something that folks need to be aware of and I thank you for bringing it up.

dj

I kind of strayed a little from the OPs question. Although looking at older (2017-) Standard Horizon VHF/AIS Rx combos, it is unlikely that his display will show more than 15 targets at once at least on the unit. Maybe more if put out on NMEA to an MFD. In 2017 a lot of surface area would have been required to receive 15 targets. Today it maybe possible to do that in a stones throw of your own slip. Depending on where he sails, a standalone antenna cut for AIS and mounted on the pushpit would be more than sufficient. If he plans on going offshore in the future then a mast head antenna via a splitter (maybe integrated in the unit) maybe a thought. If the mast is coming down then now is the time to do mast cabling.

 

[jssailem]

Len, I read your report about the BC and Washington Ferries. They are the very reason I bought my AIS. Both times that I have sailed the same waters they were traveling, they have called me. They saw my AIS signal, and we discussed our intentions and how we would avoid each other's path. The BC ferry was coming up Captain Passage on the West side of Prevost, heading for Long Harbor. We were making our way down Trincomall Channel on the East side of Salt Springs, turning West heading for anchorage in Annette Inlet on Prevost.

The BC Captain called our boat by name. We agreed to pass Starboard to Starboard. The fog and snowfall were so dense all we observed was a large dark shadow passing.

AIS is a powerful safety tool. I often check it. Sitting in a marina, I see multiple targets. When out on the water, it has not been an issue. I am usually set on a 10nm radius unless I am crossing waters where I know the ship traffic will be at high speed, like the Juan D'Fuca or Haro Strait.