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Old 10-02-2010, 08:55   #1
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Comar AIS Receiver and Splitter

I am actually evaluating AIS receivers. Does anybody have experience with Comar AIS receiver & splitter? Is this a good choice or is the ICOM MXA-5000 the better one? Thanks for any reply.
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Old 10-02-2010, 10:58   #2
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We are in the process of evaluating AIS also here at the Naval Academy for the new fleet of sailboats. I have little hands on experience with this so I can't speak for one unit or another but the one thing that I do not like about Comar splitters is that they come with pigtail cables instead of jacks on the unit. The cable for attachment to the VHF is 1 meter long and for the AIS unit, 2 meters. This limits where you can put the thing unless you want to use extension cables which I don't like to do. We've been looking at the EasySplit splitter.

Eric
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Old 10-02-2010, 11:51   #3
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Drop an e-mail to Mike Mills at Milltech Marine. He sells several different units and can advise you on which one is best for your boat. Many members of our Yacht Club have bought from him and are very happy with the selection.

Welcome to Milltech Marine - your AIS experts
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Old 10-02-2010, 13:11   #4
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I am fitting a 'Digital Yacht' AIS Transponder on Chesapeake and will report results in two weeks. Reportedly now fitted on UK coastguard vessels following trials. Looks professional kit but will report. Retails below 500 from Marine Electronic Services (mes.co.uk).
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Old 11-02-2010, 14:53   #5
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given the technology, are you not considering Class B transponders
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Old 11-02-2010, 22:24   #6
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Last two boats I have raced offshore & delivered have had the comar receiver and splitter. It's a good piece of kit.

Three things I'd consider:

1. Consider spending a bit more and going for the Transponder - you can see the big ships, the problem is that they may not see you.

2. For the price of the splitter, you can almost get a 2nd VHF ariel. Then you don't have the dilema of "do I listen to 16 or do I see what ships are around?" You can't do both. Having said that, it's only really a problem in very congested water ways (for me - Singapore - you really need to be on both at the same time - we used handheld vhf and AIS permanantly on)

3. Consider 2nd hand. ISAF have just made AIS Transponders a requirement for Cat 1 races. There are a lot of race boats getting rid of their Recievers at the moment - ask around.
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Old 12-02-2010, 00:30   #7
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We have a NASA Marine AIS Engine II interfaced to a Northstar cahrt plotter that sits in the cockpit and is always on...we have a separate VHF aerial on the pushpit...the Northstar plotter allows you to set alarms for distance, speed, bearing, circle and combinations of these for approaching vessels...it's very good.

I'm not so sure about having a Class B transponder on a small yacht....the problem is that these big ships often don't keep proper watches...the age old problem...just 'cos your transmitting a signal, doesn't mean that they're gooing to see you....much better I think to avoid them !
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Old 12-02-2010, 02:27   #8
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Quote:
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I'm not so sure about having a Class B transponder on a small yacht....the problem is that these big ships often don't keep proper watches...the age old problem...just 'cos your transmitting a signal, doesn't mean that they're gooing to see you....much better I think to avoid them !
Much better to avoid them - I'm definately with you on that one - most of the time you can avoid a 'risk of collision' situation before it even develops.

But the reference to big ships not keeping a proper watch - what are the views on this? I would have thought that now that AIS is required on everything over 300 tonnes (I think) that it actually improves the situation. Wouldn't they just set the proximity alarm on the AIS, set the proximity alarm on the Radar and then anything that has a decent radar signal and AIS transponder is pretty much always going to set off an alarm.

Can anyone with experience of being on the bridge of these types of vessels comment? What is standard operating procedure?
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Old 12-02-2010, 04:07   #9
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2. For the price of the splitter, you can almost get a 2nd VHF ariel. Then you don't have the dilema of "do I listen to 16 or do I see what ships are around?" You can't do both.
Yes, you can do both. That's what the splitter is for. There are splitters for use with AIS transponders. The transmission time for AIS is so brief, around 26 milliseconds, you barely notice it even when listening to a conversation on your VHF.

Eric
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Old 12-02-2010, 05:10   #10
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I can recommend the Comar CSB200 Class B AIS Transponder. I was initially a little disappointed with the range of my transmitted signals as reported by other yachts, but have found that I rarely get any better results myself from other Class B transponders - typically no more than 8nm although have received Class A transmissions up to 70nm with the antenna on the backrail!

BTW strongly recommend a separate antenna for AIS whether plain receiver or transponder. IMO splitters are just a bodge albeit a sophisticated one to suit lazy people.
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Old 16-02-2010, 18:31   #11
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Re the splitter.

The two I have used to date have been a physical switch that you operate by hand that connects the VHF antenna to either the radio or the AIS unit.

Sounds like technology has moved on and fairbank56 may have the answer for this dilemma - he describes a unit which automatically switches to AIS when the unit needs to send.

However (and with no knowledge of this system I should stress) I'd enquire how often it switches over to receive - if it is sophisticated enough to switch to AIS every time it receives, then this is OK for the AIS - but may interfere with radio calls - especially in busy areas where signals are being received every few seconds.

Even with this technology, I would personally be more comfortable with a 2nd antenna - simply because I live in an area with high boat traffic - low traffic areas it would be less of an issue and if you carry a handheld vhf, less of an issue still.
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Old 16-02-2010, 18:56   #12
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Both your normal VHF and AIS can receive simultaneously. The splitter immediately detects transmission from either and disconnects the other. Your AIS transmission is extremely brief, around 26 milliseconds, so even if you are carrying on a conversation on your VHF, you'll barely notice the dropout when your AIS transmits. It's not about being too lazy to install another antenna. You'll get the greatest range with antenna on the masthead for a sailboat and you can't have both antenna's up there.

Eric
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Old 16-02-2010, 19:06   #13
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Kind of hard to justify the cost of some of the AIS receivers with the drop in price of AIS class B transceivers. I had a Smart Radio SR161 receiver (~$189 + shipping from Milltech Marine) for several years and decided to upgrade to a class B unit in my high traffic area. Bought a West Marine AIS-1000 for under $500 (and less with a few West discount offers) that came with its own GPS and used the same VHF antenna. Even sold the old SR161 on eBay for $125, so not much of an upgrade cost. And a friend just went for an ACR transceiver for $700 that included both of the antennas. Looks like the receiver vendors have simply held on to their old pricing.
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Old 16-02-2010, 19:32   #14
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Guys why are you even talking about antenna splitters with all their expense, complexity & potential unreliability.

PLEASE just route your AIS receiver or transponder to a dedicated antenna. It really will work out cheaper. One mounted on the back rail will be more than adequate to give you plenty of warning of potential traffic threats.

Lets face it - do you really want to compromise a not inexpensive device designed to improve your safety at sea?
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Old 16-02-2010, 19:49   #15
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Now fairbank56 has explained the system, I can see benefits of both set ups:

Use a splitter and get better range

Use a dedicated antenna and have less bits to go wrong (and have a 2nd emergency antenna ready to go incidentally).
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