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Discussion Starter #1
Good afternoon on this windy wet Sunday.
I am considering getting a EM Track AIS with antenna splitter to use the excising masttop VHF antenna. I have a SH 2200 VHF with AIS receiver will this cause any problems since then the AIS transponder uses the same antenna as the VHF radio with AIS receiver?
How about the CPA alarm?
Is there anybody with a comparable set up?

Sail Ahoy, Hein :2 boat:
 

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Why don't you get a separate antenna.... you can use as a spare if the other fails.
 

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I have a Vesper XB 8000 AIS and their splitter with my VHF antenna on top of my 63' mast and have experienced no problems. Make sure you use high quality cables and quality connections and you should be fine. I do carry a spare antenna that can be mounted on my pulpit should I have a problem but never have had an issue.
 

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Sanders point is mine also .

I have my Vesper AIS set up on a separate antenna on my rail. I have no issues getting 24-36 miles and offshore almost 48 nm. Plenty of time for any avoidance.

That was if the one antennae should fail I have a backup. Redundant systems in a marine environment make sense.

As far a difficulty to self install, it one of the simplest DYI installations there is. It’s not hard at all to install an antenna to the rail and lead the cord back to where you are going to install the AIS unit.

BTW if/ when your mast top antennae fails wither it’s a contact or bird induced you could tale the wire from the VHF and put it temporarily to the rail unit easily.
 

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Discussion Starter #6
Guys thank you for the advice, but with a separate antenna I am sure the SH 2200 with AIS receiver will have a CPA of 0 and therefore a continuos alarm going off.
 

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Guys thank you for the advice, but with a separate antenna I am sure the SH 2200 with AIS receiver will have a CPA of 0 and therefore a continuos alarm going off.
I doubt that. Ours doesn’t show that reading on the rail
Our radar is pole mounted 15 ft above rear rail. It scours at 48 miles. If CPA was 0 I would have moved the AIS antennae there. I am posting this as others may have similar questions. I was at this question a few years ago when I purchased my Vesper. I like having the backup already in place and installed. Before that I used to carry an emergency antennae, a safety consideration as our handheld gets maybe 3 miles range. Now I don’t have to, it’s already in place.

You’ve already identified you are following the procedure you came here with looking for affirmation to. We given you some alternatives Let us know in 5 years whether you have experience any issues
 

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We have the SH 2200 sharing an antenna through a Vesper splitter with a Vesper 8000 AIS transponder. Works fine. As long as you have the same MMSI number in each unit, the SH2200 will ignore the AIS transponder. If connected to a plotter or other display, you can only connect the transponder, or you will see yourself chasing yourself around on the plotter.

IMO height trumps a separate antenna mounted lower. There are no losses through a good splitter (some actually provide additional gain), and the installation can be much easier depending on the boat setup. For example, running a separate antenna system on our boat would put the spreader as the least onerous place to do so. Having a backup antenna is over-rated - how many times has yours failed? If a failure does occur, most people have a handheld, and most cruising boats carry a spare antenna and some coax anyway. Splitters have a lower failure rate than the radios connected to them.

The one downside of using a splitter is that the AIS does not transmit while the VHF is transmitting. So if you talk for long periods of time without releasing the mic key, you will lose AIS transmission during the talk period. Since talking on the VHF is not a habit of ours (quite the opposite), it is not an issue for us.
 

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Guys thank you for the advice, but with a separate antenna I am sure the SH 2200 with AIS receiver will have a CPA of 0 and therefore a continuos alarm going off.
You would think that by sharing an antenna the AIS receiver would not pick up the AIS transmission, but reception does occur while transmission is active. So if you connect your SH2200 to your chartplotter, you will see yourself on it.

The SH2200 is smart enough to know it is you and not display ownship on its display, nor cause alarms - as long as the MMSI number is the same on both.

So if you want the data on a chartplotter, connect the transponder's output to the plotter, and connect only the SH2200 DSC data wires to the plotter. Leave the SH2200 AIS data wires disconnected.

Mark
 

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Third vote for a separate antenna. A range of 6 to 8 miles is more than enough especially when coastal. We have a splitter but also cabling to another antenna on top of Bimini. It’s two seconds to switch to which ever of the two antennas for whatever function you what. Belt and suspenders. I mostly want to see ships when at sea and local traffic when coastal. A strong reliable signal with quickly getting course and closest intercept at a range that’s relevant is what’s important. See ships 10-16m reliably or better or even farther with the lower antenna. That’s plenty. Even 6 m is plenty when coastal. Suspect you’ll get that wherever you put the antenna. It’s line of sight. So the height of the sending antenna as well as receiving both are important.
 

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Fourth vote for separate antenna.

I have a Vesper XB-8000, and a Raymarine VHF 50. Both my Shahespeare antennas are mounted on the pushpit, and they are mounted co-axially. If there is ever any problem with either VHF or AIS, I don't have to go up my 47' mast.
 

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For antennas on a pushpit, at a height of 6' each, a perfect AIS signal will be received between them at 6nm. Rarely do people have perfect antenna systems, so count on some power loss of that whopping 2W, and reception is probably less than 6nm. Class B AIS power output is less than half of a handheld VHF - and many people struggle connecting with them at 6' heights over any reasonable distance.

Some may argue that 4-6nm is fine for them, but I don't. I want to see as far as possible - particularly in less than perfect conditions with multiple targets. For example, I don't want to be working a fast class A ship avoidance tactic and suddenly need to recalculate and change at the last minute because another smaller ship appeared at 4nm interfering with my original plan. This is a common situation entering busy harbors and ports.

Those of you thinking you are transmitting 6nm, I suggest getting a good report verifying this. So many boaters have poor antenna systems that we encounter many AIS signals popping up at 2-3nm from boats thinking they are being seen 10nm+.

I've yet to hear a convincing argument against higher antennas or using splitters for AIS. The argument of a splitter degrading the signal is bogus for today's splitters. The argument of redundant systems only rings true if that is carried further than just a cable and antenna - do you have redundant VHF and AIS radios? Redundant autopilot? Redundant engines? Redundant rudders? Where does this line of reasoning stop, and why only at AIS? Is it because redundancy throughout all boat systems is too onerous, so one just picks something easy and places a flag on it?

FWIW, we have redundant systems for all the above and more, except for a redundant AIS transponder (have a second AIS receiver, though).

The only valid argument is if one talks on the VHF so much, and so long, that it precludes their ship's AIS transmissions.

Mark
 

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Pretty easy to do. Use the d-man thing. Tap AIS data. See how far away the ship is. You get everything you need to avoid it. Easy to place a vector line to show. Even without that not hard to dodge multiple ships or targets after you’ve look at the data for each. We have the vector line setting on always. Always a good idea to recheck as just like us ships have rudders. Unlike us they change speed more frequently. So I’m checking them out continuously. And it’s when they get close that it really matters. Don’t see how range makes any difference in a harbor. Is helpful offshore but that’s a different kettle of fish. Then I’ve yet to have more than two or rarely three targets so a degree or two change on the AP or vane serves. Only tap +10 in the setting you raise where range doesn’t matter.
Found using the masthead antenna and splitter targets would show then disappear. Then show again once they got closer. Troubleshooted it to the point of replacing the coax. Now have access to the masthead antenna if I want it for AIS but usually used the dedicated antenna. Don’t know if the longer run is the issue (65’ plus ~20’), interference someplace in the run (have ferrites everywhere I think their needed) or what. But have never had issue with the lower down one. It’s run is maybe 15-20’. So we’ll agree to disagree. Still, like the idea of 2. Redundancy for both VHF and AIS for a days work and a couple of hundred bucks.
 

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. Still, like the idea of 2. Redundancy for both VHF and AIS for a days work and a couple of hundred bucks.
...and cheaper to boot! (price of an antenna and requisite coax is FAR less than the price of a good splitter)

I do what works for me, you do what works for you. There is no one right answer.

I don't need VHF to communicate at 6+ miles where I sail. I am not taking my 33+ year-old O'day 35 offshore to Bermuda, but I sail a lot coastally (Narragansett, Cape Cod & Buzzards bays, Long Island Sound). Most of the time I use a handheld VHF to communicate with a nearby marina or harbor master. One thing that annoys me is hearing people repeatedly hailing the Newport Harbor Master (usually on 16) while I am sitting on my mooring 12.5 miles away:rolleyes:.

My pushpit mounted antenna works great at 5 watts (low power) over land (hills, trees and houses blocking the signal) over 3.8 miles (Sea-Tow radio check nearest my mooring). The pushpit mounted AIS antenna picks up ships at over 5 miles, and class B targets at over 3. If it stops working great (as my mast mounted VHF antenna did, 6 years after installation), I can replace the entire works without pulling or climbing the mast (and I carry a spare antenna onboard). Removing the mast mounted VHF antenna lowered my air draft from 49 to 47 feet, thereby enabling me to clear the Port Mayacca Railroad Bridge on the Okeechobee Waterway (planned for later this year) without question.
 

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FWIW, combination VHF/AIS transponders are starting to come to market now, and surely will become a major product in the near future. These have integrated splitters and share the same antenna for both functions. They won't be a viable product for people adamant about keeping these technologies separate.

However, there are still those who would never combine a radar and chart plotter, nor an inverter and charger, nor a phone and computer, nor an autopilot and navigation equipment - so the market serves everyone.

Summarizing for the OP (based on 8yrs of experience with the system he asked about):
1. There is no issue at all using either a splitter, or a separate antenna system for your proposed combination of the SH2200 and AIS transponder. Your choice.
2. As long as the SH2200 and the AIS are programmed with the same MMSI number, the SH2200 will not alarm or show your boat on its data display regardless of your choice in #1.
3. If you display AIS data on your chart plotter or other devices (computer, etc), only one of the radio's AIS data can be connected to the network. Probably best to connect the AIS unit and leave the SH2200 disconnected, particularly if you are using NMEA2000 - but that choice is yours.
4. If you connect the AIS to the network, then only disconnect the SH2200 AIS data wires. Leave the DSC data wires connected to the network so that you will get DSC position data and alerts on your chart plotter or other devices.

Mark
 

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...and cheaper to boot! (price of an antenna and requisite coax is FAR less than the price of a good splitter)
Depends. Several times a year - holidays, black fridays, cyber mondays, boat shows - many AIS transponder companies offer a free splitter with purchase of AIS. This is so common that outside of these numerous times a year, one just needs to ask for the special to be extended. That's how we got ours.

But let's say one buys it anyway. The splitter is $250. That's fixed for everyone. The cost of the coax and antenna, however, varies for people. For us, we use LMR400UF @$1.59/ft and would need ~60' for a separate antenna run. We also use a good antenna @$95. Others may choose to use lower performance gear, of course, and the costs would be less - as long as one isn't purchasing from West Marine.

So we would be in for $190 to run a separate antenna system (I'm throwing in the cost of good connectors for free) vs. $250 for a splitter. Not a whole lot cheaper, and definitely not "FAR less".

For us. But this is a case by case thing dependent on boat and choice of quality.

Mark
 

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Question for the mods; Is this thread in the right place?
SailNet Community > SailNet Website Help Desk > SailNet Website Technical Support > AIS antenna splitter question
 
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