If you could do AIS from the start. Which setup makes sense.

[rslifkin]

Agreed on the separate antenna as well. I'm currently working on finding a spot for a 3rd VHF antenna for when I do an AIS install, as I don't want to run a splitter on either of my existing VHFs.

 

[Frosty]

One note on the separate antenna. It's preferable unless you don't have a good way to install two (on many of your trawlers you will have acres of choices, I realize).

You want separation of around 4' between the two antennae. If you can't achieve that it may be better to have one antenna and a good (eg Vesper) splitter. (In fact Vesper is using a splitter built into their new ~$1500 unit).

You can still mount a second antenna for a spare and have it at the ready.

Another situation might be if you have a tall mast with room for only one antenna (with proper separation). You could put VHF antenna there and AIS down lower; or, if you wanted both up high, then use the mast top antenna with a splitter and keep the lower antenna (if mounted) as a spare.

When I started shopping for AIS I was of the mind that "no way am I using some cheesy splitter!" As it turns out they are not cheesy, and also I don't have a good setup for proper antenna separation. I still mounted and ran cable for the second antenna, but as a spare.

Again, may not apply if you have a lot of real estate, but just to say separate antennae may not always be better if you can't get adequate separation.

 

[sunchaser]

We cruise in inclement weather. Our send receive AIS is hooked into radar and several plotters. We've kept up with updating the vessel information reminders. My guess is we've been hailed by commercial traffic a dozen times or more regarding our intentions in the past five years or so. Then add in the smaller vessels owned by friends picking us up and calling us to get updates etc. Many times fishing vessels have called to alert us to net and float placement.

Today's AIS units are cheaper than an Apple, have no monthly fees and work just fine where there is no cell coverage. In our cruising areas we are invisibly monitored (historic and current) by the eye in the sky 24/7, a great safety tool if ever needed.

Along with a PFD, life raft and ditch bag, we consider AIS an essential device for our cruising plans and locations. But that is just us.

 

[rgano]

If you are going to be running waters with lots of bends and/or commercial traffic, a transceiver is invaluable. I run my current boat in local VFR conditions and feel "over-propped" with a receive-only unit. I once ran a boat halfway from the Gulf coast to Lake Michigan with no AIS. Then the owner called to tell me he wanted me to install a full suite of AIS transceiver interfaced to a new AIS capable radio and also connected to the Garmin plotter. Holy cow, what an improvement in the connection to everybody else with AIS. I especially liked being highly visible to commercial vessels rumbling by in the night while I remained anchored just off the channel due to shallow water that year.

 

[twistedtree]

I too think every effort should be made to install a dedicated AIS antenna. I realize it’s not always going to be possible or practical to do this, but long term worth while.

People get all in a dither over the very, very remote chance that a Class B transmission gets blocked due to congestion. Yet the chances seem much higher that transmissions will be lost because you stepped on them with your own VHF transmissions that
Blocked your AIS.

 

[Codger2]

I too think every effort should be made to install a dedicated AIS antenna. I realize it’s not always going to be possible or practical to do this, but long term worth while.

People get all in a dither over the very, very remote chance that a Class B transmission gets blocked due to congestion. Yet the chances seem much higher that transmissions will be lost because you stepped on them with your own VHF transmissions that
Blocked your AIS.

I agree with the above but the real estate available for a 3rd antenna was suspect at best. I connected my transceiver to the SH VHF antenna that resides on the left side of my panel, saving my primary VHF for voice communications, hailing, fog horn, etc., thus mitigating stepping on the AIS transceiver.

 

[Streff]

Thank you all for the fantastic guidance and opinions. I ended up buying a 5W AIS trans receiver and splitter that came as a bundle on a great sale. I also purchased a dedicated OEM GPS made by the AIS manufacturer. When I got home, I realized that a small square GPS was included in the AIS box. It looks like one of those gps thingy that car gps system use. Not sure how effective they are.

I have room to mount an AIS dedicated antenna on the radar arch but it will be 3’ feet away from the VHF antenna. I have 2 VHF antennas for 2 VHF units. I will probably buy the dedicated Antenna and see if I can mount it with 4’ separation.

My question is, these dedicated antennas are not going to extend anywhere as high as the VHF antennas so there is a bit of compromise on that front. Unless I am missing something.

Thank you all again

 

[BDofMSP]

The small gps antenna doesn't really need to be super "effective". It's not transmitting long distances or anything. As long as it can see the sky it should do the job.

 

[firehoser75]

Streff,
Prior to my AIS install, I experienced my then only GPS kicking off if I did a "lengthy" VHF broadcast. Interference from the VHF antenna. As part of my upgrade, I replaced the old VHF antenna with a Morad unit mounted on an extension pole to give the maximum broadcast range (a bit more). Another benefit, is that now the VHF antenna is 5 feet above the GPS antenna, no more interference!! My AIS antenna is mounted lower than the VHF antenna, but above the GPS. I also now have GPS antenna redundancy. All is well.

 

[ScottC]

Hello Streff,


I fully agree with those in this thread in favor of a full AIS Class B transceiver. I generally boat in an area prone to fog and large ships and have a Class B transceiver fully integrated with my Raymarine e127 MFD. I too had the decision to make about dedicated antenna or vhf splitter. In the end, I went with the splitter and can relay here that it has worked seamlessly for me for the ~6 years I've had it. One does not need to turn off the VHF for switching to occur. It happens behind the scenes in a fully automatic way. Never have to think about it. I can also say it's nice to have one less antenna to put down for going under low bridges. Finally, I have been surprised to see, on occasion, a feature that I was unaware of. AIS Distress alert. A boat in distress (I presume hitting the VHF DSC/Distress switch) will show up on my e127 MFD in flashing red and allow me to simply use the "go to" function.


Best regards,
Scott C

 

[Codger2]

Hello Streff,


I fully agree with those in this thread in favor of a full AIS Class B transceiver. I generally boat in an area prone to fog and large ships and have a Class B transceiver fully integrated with my Raymarine e127 MFD. I too had the decision to make about dedicated antenna or vhf splitter. In the end, I went with the splitter and can relay here that it has worked seamlessly for me for the ~6 years I've had it. One does not need to turn off the VHF for switching to occur. It happens behind the scenes in a fully automatic way. Never have to think about it. I can also say it's nice to have one less antenna to put down for going under low bridges. Finally, I have been surprised to see, on occasion, a feature that I was unaware of. AIS Distress alert. A boat in distress (I presume hitting the VHF DSC/Distress switch) will show up on my e127 MFD in flashing red and allow me to simply use the "go to" function.

I have exactly the same set up on my boat but did not know about the "AIS distress alert."
Thanks, Scott for the heads up!

 

[ranger58sb]

I have exactly the same set up on my boat but did not know about the "AIS distress alert."
Thanks, Scott for the heads up!

It depends on your whole set-up. Your plotter has to be able to recognize and handle that from other boats and it may well do that... but you also may need the correct connections from VHF to plotter to get a VHF distress call displayed.

Our plotter will do the same thing BUT... in our case I'd need to connect the NMEA0183-out wires from VHF to plotter. For some reason our installer didn't do that, and the plotter won't receive AIS sentences via the already-connected NMEA2000-out from radio to plotter.

It took me some years to figure that out. Now that I've understood... I still haven't bothered to make the physical connection.

-Chris

 

[DDW]

When I got home, I realized that a small square GPS was included in the AIS box. It looks like one of those gps thingy that car gps system use. Not sure how effective they are.

Pretty much every AIS has it's own GPS receiver. The small square thing is the patch antenna for the GPS. They are quite sensitive these days. You can probably mount it underneath the overhead (ceiling, for you powerboat guys ) as fiberglass its pretty transparent to GPS frequencies. It won't go through a wood deck or a bunch of superstructure well but no problem with even thick deck laminate. Of course try it first.

 

[ScottC]

I digress, but this discussion made me reflect on just how many gps receivers I now have on board: MFD, AIS, VHF, VHF-Hand Held, YachtSafe alarm w/ GeoFence; Victron Global Remote w/ GeoFence, ZipWake interceptors, 2 iPhones and a partridge in a pear tree...


Seems to be fewer and fewer opportunities to exercise dead-reckoning & position bearing skills these days ;-)

 

[twistedtree]

I believe the whole distress thing is based on DSC in your VHF, and has nothing to do with AIS. Or let's put it another way. DSC definitely has that capability, and is a good reason why you should correctly hook up your VHF and chart plotter. If someone pulls the alarm on their boat, the alarm and their location will show up on your chart plotter.


Their might be a parallel capability in AIS, but I'm thinking no. Does anyone know otherwise?

 

[rslifkin]

I believe the whole distress thing is based on DSC in your VHF, and has nothing to do with AIS. Or let's put it another way. DSC definitely has that capability, and is a good reason why you should correctly hook up your VHF and chart plotter. If someone pulls the alarm on their boat, the alarm and their location will show up on your chart plotter.


Their might be a parallel capability in AIS, but I'm thinking no. Does anyone know otherwise?

As far as I know, you're correct, it's just DSC, not an AIS function. AIS receivers do receive DSC distress calls, however, so even if the VHFs aren't connected you'll get the alert on the plotter from the AIS.

 

[ScottC]

I believe the whole distress thing is based on DSC in your VHF, and has nothing to do with AIS. Or let's put it another way. DSC definitely has that capability, and is a good reason why you should correctly hook up your VHF and chart plotter. If someone pulls the alarm on their boat, the alarm and their location will show up on your chart plotter.


Their might be a parallel capability in AIS, but I'm thinking no. Does anyone know otherwise?

Hi Twisted Tree - I suspect you are right, but that leaves me puzzling why the alert on my e127 MFD actually says "AIS Alert" on the little boat symbol on the screen. While my Ray63 VHF has GPS, it does not have AIS.
My AIS is a CTRX Graphene and nowhere in the documentation does it mention anything about a distress alert. So honestly, I do not really know which piece of equipment is primarily responsible for this seemingly undocumented feature. Nice that it works, however!

 

[ranger58sb]

As far as I know, you're correct, it's just DSC, not an AIS function. AIS receivers do receive DSC distress calls, however, so even if the VHFs aren't connected you'll get the alert on the plotter from the AIS.

Yes. I mis-spoke a bit earlier; I was thinking about DSC position reports received by VHF and then to be displayed on the plotter.

-Chris

 

[twistedtree]

Hi Twisted Tree - I suspect you are right, but that leaves me puzzling why the alert on my e127 MFD actually says "AIS Alert" on the little boat symbol on the screen. While my Ray63 VHF has GPS, it does not have AIS.
My AIS is a CTRX Graphene and nowhere in the documentation does it mention anything about a distress alert. So honestly, I do not really know which piece of equipment is primarily responsible for this seemingly undocumented feature. Nice that it works, however!

I think rslifkin has the explanation, and as I think about it, I experienced exactly this on my boat. I had a faulty VHF that would occasionally generate DSC distress calls. I know, not a good thing. I now recall that it was my AIS that went bonkers when the alert came in, and aft a little bit I realized the call was from MY mmsi . Then it happened again a few days later which is when I realized I had a defective VHF, actually a defective remote. Replaced that and all was well.


But yes, the AIS receives the alerts, and it creates a data path for those alerts back to the chart plotter that might not otherwise exist directly from the VHFs.

 

[ScottC]

I think rslifkin has the explanation, and as I think about it, I experienced exactly this on my boat. I had a faulty VHF that would occasionally generate DSC distress calls. I know, not a good thing. I now recall that it was my AIS that went bonkers when the alert came in, and aft a little bit I realized the call was from MY mmsi . Then it happened again a few days later which is when I realized I had a defective VHF, actually a defective remote. Replaced that and all was well.


But yes, the AIS receives the alerts, and it creates a data path for those alerts back to the chart plotter that might not otherwise exist directly from the VHFs.

Wow - I didn't know such a defect was possible! What an unfortunate and embarrassing situation. My first thought after reading this was 'good thing that all the rescue forces did not descend upon you!' But, after thinking about this, it's quite disturbing that it did not produce a bunch of immediate responses offering help.



I know, for the few times I've seen this alert on my MFD, that it wasn't my MMSI, because I happened to note the numbers and the locations (which, in all cases, were too far away for me to provide any quick on-site help, given how slow my boat goes). Anyway, I now know to be on the alert for the possible scenario you described!

 

[twistedtree]

Wow - I didn't know such a defect was possible! What an unfortunate and embarrassing situation. My first thought after reading this was 'good thing that all the rescue forces did not descend upon you!' But, after thinking about this, it's quite disturbing that it did not produce a bunch of immediate responses offering help.

Oh, but it did.


The first time I was at a dock in Dana Point, and within just a few minutes the Harbor boat and sheriff's boat were off my stern asking what was going on.


The second time I was passing Long Beach at night and the Coast Guard was on the VHF to me in about 5 seconds. And they recognized me from a few days earlier. That's not a good thing.


I'm not remembering all the details, but I think the first time I somehow knew it was the remote that had triggered the alarm, so I swapped with another remote to see if the problem followed the remote or stayed with the VHF (two VHFs, two remotes). The Long Beach incident confirmed it was the remote so I disconnected it and returned it to iCOM. It was brand new. Everyone was puzzled over the fault, but they sent me a new one and it never happened again.

 

[Xsbank]

What I am reading here is opinions on whether a dedicated antenna is better than a splitter. Anybody got any evidence or is this a synthetic oil/anchor opinion? How could a splitter get certified if it wasn’t reliable? Same as Standard Horizon couldn’t get their AIS combo radio certified.

 

[rslifkin]

Splitters are reliable, but they usually cause a small amount of signal loss for both vhf and AIS. On top of that, you lose AIS transmit and receive while transmitting on that VHF. Because of those factors, if it's reasonable to run a separate antenna, it's better. Plus, if you damage an antenna somehow you'll lose less functionality.

 

[LarryM]

I believe the whole distress thing is based on DSC in your VHF, and has nothing to do with AIS. Or let's put it another way. DSC definitely has that capability, and is a good reason why you should correctly hook up your VHF and chart plotter. If someone pulls the alarm on their boat, the alarm and their location will show up on your chart plotter.


Their might be a parallel capability in AIS, but I'm thinking no. Does anyone know otherwise?

Like you, I'm not aware of any AIS distress signaling capability for vessels, but AIS MOB beacons have been available since about 2011. The earliest was the McMurdo S10. More recently, I'm seeing the the ACR AISLink as a popular MOB rescue device. Unlike PLB's which signal orbiting SAR satellites, these devices immediately send an alert to all vessels within about 4 miles that are equipped with AIS receivers and/or AIS-enabled plotters. They can also alert the crew to the MOB by activating the DSC alarm on the vessel's VHF.

Could this be a possible source of the "AIS Alert" ScottC and others were discussing?

 

[ScottC]

In my particular case, Larry M, the few alerts I've seen were all much further than 4 miles away.

 

[Cigatoo]

What I am reading here is opinions on whether a dedicated antenna is better than a splitter. Anybody got any evidence or is this a synthetic oil/anchor opinion? How could a splitter get certified if it wasn’t reliable? Same as Standard Horizon couldn’t get their AIS combo radio certified.

I talked with a well respected Marine Electronics installer. They said that overall they have had less problems with splitters than with multiple antennas causing interference.
Sailboats only have room for one antenna for the most part so splitters are the norm in that world.

 

[rslifkin]

I talked with a well respected Marine Electronics installer. They said that overall they have had less problems with splitters than with multiple antennas causing interference.
Sailboats only have room for one antenna for the most part so splitters are the norm in that world.

I'll absolutely agree that a splitter is better than multiple poorly installed or haphazardly placed antennas. But with a little thought and care, most decent size powerboats can handle somewhere between 2 to 4 VHF antennas with appropriate spacing. Even a sailboat can manage more than 1, but only 1 will be at the top of the mast for maximum range.