AIS Splitter question

[jackho]

Most sailors i know who have recently fitted AIS have included the splitter option (which in some cases is nearly half the cost again).
When I purchased mine (Vesper) the agent advised a separate aerial if possible, probably mounted on the guardrail. This was based on the safety first principle of always having a backup to the main VHF aerial. especially critical if a yacht is dismasted.
Am I missing something?

 

[PaulRainbow]

Most sailors i know who have recently fitted AIS have included the splitter option (which in some cases is nearly half the cost again).
When I purchased mine (Vesper) the agent advised a separate aerial if possible, probably mounted on the guardrail. This was based on the safety first principle of always having a backup to the main VHF aerial. especially critical if a yacht is dismasted.
Am I missing something?

Nothing wrong with what you have (although i'm sure someone will be along soon with tales of woe and poor range for the AIS because the antenna isn't high enough). More and more AIS transponders are being produced now with built in GPS and built in splitters, but that doesn't mean that one cannot have a backup VHF antenna on the pushpit. I have a black box VHF/AIS, so no need for an additional antenna or a splitter, but i also have a backup antenna on the pushpit with the cable clipped next to the VHF, ready for use. Due to an issue with the masthead antenna i'm currently using the "emergency" antenna. reception is still perfectly adequate (in fact, hard to see much difference with the AIS targets), motorboats seem to manage, without masthead antennas.

 

[lustyd]

It's not either or, you can have a splitter and a spare antenna.

I went for separate on the rail for AIS. I can see (from the marina) the same range as the mast top antenna but would expect the mast top to be "better" when at sea. I have sufficient range for a ship to easily alter course while crossing the channel when they see me which is fine for me

 

[jackho]

Nothing wrong with what you have (although i'm sure someone will be along soon with tales of woe and poor range for the AIS because the antenna isn't high enough). More and more AIS transponders are being produced now with built in GPS and built in splitters, but that doesn't mean that one cannot have a backup VHF antenna on the pushpit. I have a black box VHF/AIS, so no need for an additional antenna or a splitter, but i also have a backup antenna on the pushpit with the cable clipped next to the VHF, ready for use. Due to an issue with the masthead antenna i'm currently using the "emergency" antenna. reception is still perfectly adequate (in fact, hard to see much difference with the AIS targets), motorboats seem to manage, without masthead antennas.

yes agree with all you say but my issue is why are sailors paying up to £300 for a splitter - enough to pay for 3or 4 antenna. is there some benefit thats not obvious.

 

[lustyd]

Yes. It took me almost three days to install my stern mounted antenna and GPS puck, and I now have two more potential leaks in my deck and two more bits of kit in places where they could be more easily damaged. The extra puck is realistically not optional (although the built in GPS works surprisingly well below decks) but the VHF antenna is and could reduce effort to use a splitter. the difference between a £100 antenna plus fittings (approx £50) and sealant (£10) plus labor (£who knows!) and a splitter is probably approaching zero.

 

[PaulRainbow]

yes agree with all you say but my issue is why are sailors paying up to £300 for a splitter - enough to pay for 3or 4 antenna. is there some benefit thats not obvious.

The only "benefit" is that you don't have to run the cable to the pushpit.

But, as i said previously, many of the latest AIS have (or are have as an option) built in splitters. For instance, the Emtrak B921 does not have a splitter, but the B923 does and only costs just over £100 more. I can't remember the last time i fitted one with the built in splitter, the extra cost is less than buying an antenna and mount, let alone the labour of fitting it. Both models have built in GPS, so with the built in splitter there is no need for extra holes in the boat, unless one wants a backup VHF antenna.

 

[lustyd]

Oh, I also did approximately 30,000 steps walking, plus 60 flights of stairs according to my Garmin. The boat is 36' and has 4 steps to the cockpit as well as the drop into the stern locker. It also has factory fitted cable ducts to make cabling "easy". The factory also, apparently, had something of a fetish for zip ties!

 

[jackho]

The only "benefit" is that you don't have to run the cable to the pushpit.

But, as i said previously, many of the latest AIS have (or are have as an option) built in splitters. For instance, the Emtrak B921 does not have a splitter, but the B923 does and only costs just over £100 more. I can't remember the last time i fitted one with the built in splitter, the extra cost is less than buying an antenna and mount, let alone the labour of fitting it. Both models have built in GPS, so with the built in splitter there is no need for extra holes in the boat, unless one wants a backup VHF antenna.

Think my question is answered. No additional benefit apart for the obvious. Also price difference perhaps less now than when i last checked.

 

[Bathdave]

I weighed this up and concluded a separate aerial with a cable run by the guy installing the AIS would cost pretty much the same as the splitter ...the guy was pushing to go the splitter route (surprise - same money less work and running cables can be fiddly)

I don’t recall the splitter being £300 either ...

biggest downside as far as I am concerned is you don’t have contingency/resilience with your VHF masttop ariel.

 

[lustyd]

One other thing to consider is that unless you have a new antenna up the mast you might want to take the opportunity to at the very least re-cable that if using it for both and not having an alternative option. Once you've seen the inside of an old antenna cable (mostly white dust, formerly metal) this becomes much more of a concern! Usually the first two feet are beyond usefulness after a decade or so, at both ends of the cable.

 

[prv]

Yep. I'm using a splitter because I didn't want to clutter up the stern with extra gubbins and warp-catchers and flag-tanglers. Or have to squeeze yet another cable through the over-full space above the heads locker and around all the plumbing in the cockpit locker. Keeping all the work within the electrical space behind the chart table was well worth the price difference for me.

I don't see the extra range of a masthead AIS antenna as particularly important, and my backup VHF antenna is one of those packed-in-a-tube ones, in a locker.

Pete

 

[Kerenza]

unlikely to interest you, but cat 3 and above offshore racers are required ether a splitter with the masthead vhf or separate aerial more than 3m above the water and less than 40% power loss cable. i guess they have their reasons.