AIS & Splitters - Update?

Athene V30

Athene V30

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Last year there was a thread about AIS and splitters. 2007 thread The comments tended to be against splitters. I am looking to fit AIS and display on Standard Horizon CP300 and use it with CPA alarm as a 'lookout' when in less congested waters. Not got loads to spend (probably £250 max) - cannot afford (or really want) radar. Should I hold off and save up for the transmitting type as well?

One year on presumably there is more, newer and maybe better kit about. What is the thinking now?
 
If possible I would install a second aerial to receive AIS. Mine worked well enough on a bracket 10 feet up the backstay.
A splitter may be economical if you have to pay someone to route the cables though! Or if routing the cables is too hard!
 
1) I'd use a separate antenna - the arguments have been gone through enough times ... redundancy and reliability should be all that's needed to say

2) I'd now go for one of the duplex receivers - not convinced about the transceiver yet. The NASA units receive on both channels, but one at a time. The more expensive units receive on both channels - testing in the Solent shows that there can be a significant delay in receiving all the data when using the single channel type - less important if you're sailing in open water - but then in the Solent AIS is hardly collision avoidance, but it does give early warning on when the big ships are on the move.

I'd not go for a transmitter type atm as I don't believe the "benefits" are worth it ... may be if I was running flotillas - it could be used to keep an eye on the fleet, or if sailing regularly "in company" - but I don't think it'd form part of my "collision avoidance" - reason being is that big ships I'd start looking at MILES away as I want to miss them by a large margin, where as small vessels can be missed by small margins and I'd be looking at a more literal interpretation of the colregs ....
 
I use a Comar AIS transceiver unit with and Easysplit unit. My Icom radio shares the masthead aerial with the AIS. I have had no problems with this set up and the AIS reception is fantastic (compared to previous NASA unit).
 
I got a splitter with a bundle deal so effectively very cheap. Eventually though I installed my new DSC radio to a dedicated masthead radio and installed a second antenna on the rear arch for AIS. I then put the splitter in the AIS line and used the other outputs for my old non DSC radio and FM radio. It all works OK and I have the old radio as back up if I was ever dismasted or something went to poo with my DSC one.
Lessons learnt?
1. The splitter does not degrade the AIS function and AIS does not need an antenna at masthead to work OK.
2. There is no noticable difference on old VHF with or without splitter in circuit
If it was the only radio I had I would either
a) fit a second antenna for AIS lower down rather than a splitter
or if this was difficult
b) use the splitter but install it very near the VHF so that if it goes to poo you can put the antenna directly into the VHF.

AIS is good to have but VHF is essential
As far as AIS b is concerned (the transmitting type) IMHO forget it. If you are that paranoid about collision avoidance save up for a SeaMe instead.
 
just to mention I see Icom now do an AIS with splitter built in. Not sure its any cheaper, but I guess easier to fit, and well,it is Icom ! About £300
 
I have some patch leads that allow me to switch AIS reception from masthead to stern rail.

The masthead range is excellent. Last year 8 miles south of Portland Bill I was picking up two Land based AIS stations on the other side of the Channel. (Why don't the authorities name them!)

I was going to buy a splitter until I realized it was a powered device.

The case for a class B transmitter is getting stronger each year. A couple of years ago the feeling was most merchant ships just had minimal AIS equipment on the bridge. But now I hear more ship to ship close encounter conversations where the officers quote their AIS CPA's.
 
The case for a class B transmitter is getting stronger each year. A couple of years ago the feeling was most merchant ships just had minimal AIS equipment on the bridge. But now I hear more ship to ship close encounter conversations where the officers quote their AIS CPA's.
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Don't agree. Ship to ship AIS is class A. Very few have the capability of seeing class B (not quite sure of my facts here but would be interested to hear from any commercial bods on the subject as I know there are some on here)
What I do know is that the latest ship sets are able to turn off B and I can see why they would want to as if everyone had B from 20ft up it would be totally overwhelming. I know as far as I am concerned I don't want to see other yachts as they are seldom a threat. What I want to see is big fast chaps that could kill me and if I could switch off B I probably would if everyone and his little sister was transmitting on it..
 
To add to this. I've got an Standard Horizon CP300. With the current firmware on the set (the original one from manufacturing date) it actually ignores all Class B transmissions anyway. I'm happy with this because of the reasons already mentioned.

And yes I'm using dual antenna as well. The AIS one can also serve as a backup for the VHF in case the mast decides to go overboard (hopefully never!)

Arno
 
Agree....
I have the SH 500. didn't know that it ignores B but glad it does! Thanks /forums/images/graemlins/smile.gif
 
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Don't agree. Ship to ship AIS is class A. Very few have the capability of seeing class B (not quite sure of my facts here but would be interested to hear from any commercial bods on the subject as I know there are some on here)

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I am not sure of my facts either but from a technical perspective class B essentially alters the rules for broadcasting into a free AIS slot. I suspect on the display side a software developer would have to put code in to filter out AIS broadcast slots that contain details from a class B source.

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What I do know is that the latest ship sets are able to turn off B and I can see why they would want to as if everyone had B from 20ft up it would be totally overwhelming.

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Nonsense. 20 miles offshore leisure boats are few and far between. Running down a sailing yacht mid channel could seriously blight a merchant officer's career so I doubt class B filters will be applied offshore unless a ship is in the middle of the JOG race fleet.

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I know as far as I am concerned I don't want to see other yachts as they are seldom a threat.

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It proved useful to me last year. Mid Channel in the dark with 20 kts up my tail I had to cut across the path of a class B yacht that had been gaining on me, in order to reef my main. The AIS gave an exact picture of events.

Then there is the value of keeping track of yachts by name. After that reefing incident I lost touch with "Nordic Lady" but then 12 hours later we converged entering Plymouth. AIS gave me added value that even though during the night Nordic Lady had tracked down the Alderney separation zone and I had gybed off into Lyme Bay neither of us gained an big advantage.
 
Well my little old NASA "Radar" AIS sees Class B transmissions as well as Class A. Handy because a lot of fishermen are fitting Class B transponders and I like to see them coming too.

I thought the RTCM specified ability of a Class A transceiver to switch out "silent" targets would only temporarily suppress the the Class B targets, after 30 seconds they would start popping up again.

I use an easy AIS splitter, but have two VHF antennas. The splitter separates my two VHF tranceivers and the AIS has an antenna to itself. I'll go for Class B when the prices stabilise.
 
I bet you'd find a decent second-hand radar for £250. Much better than AIS.
 
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