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Old 06-07-2015, 12:38   #31
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Re: AIS antenna: masthead or rail mount

Thanks all.... the consensus seems to be that higher is better but rail mount may be sufficient for starters at least. I couldn't seem to see a consensus on splitter or not. I suppose having a completely separate antenna (no splitter) is prudent in the unlikely event the main stick falls down.
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Old 06-07-2015, 14:13   #32
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Re: AIS antenna: masthead or rail mount

Very interesting and informative thread---

Sorry for being dumb about this but I have a couple of basic questions about AIS:

1) if you use a splitter on your VHF antenna will you still be able to automatically hear and transmit on VHF while you are using your AIS or do you have to manually switch back and forth from AIS to VHF to AIS etc?

2) is it difficult to install a splitter, can it be installed next to your VHF radio set, and does it require any special programming ? I have a 55 ft mast and really at my age (72) I do NOT enjoy going up a 55 ft mast

3) what if you are also using your VHF antenna as a AM/FM radio antenna--will that be a problem?

4) Lastly any particular brand and model people can recommend for a AIS/VHF splitter --money isn't a real concern (within reason) but as it would be a DIY installation simplicity of installation is highly desirable (I am not particularly electronics savvy but can read instructions -for example I have successfully installed my own autopilot and wind, depth and speed instrumentation)

Thanks ahead of time for any help or advice

John
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Old 06-07-2015, 14:20   #33
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Re: AIS antenna: masthead or rail mount

Masthead. AIS can work farther either receiving or transceiving at the mast top than radar can at the spreaders and can give you a TCPA of huge ships you want to avoid (or to be seen by).

It is a great compleiment to radar in this way. Consider that if you are approaching land you can't yet see with radar, but you can see by AIS a pretty clear TSS in front of the land, you get more information than just a GPS lat/lon that tells you "you are 40 miles from shore". The AIS reveals that you are perhaps 25 miles from the sealanes. Those are things I want to know.
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Old 06-07-2015, 14:32   #34
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Re: AIS antenna: masthead or rail mount

There is an alternate solution not yet mentioned...give your masthead antenna over completely to AIS, then use handheld VHF. Cheap solution.
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Old 06-07-2015, 15:04   #35
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Re: AIS antenna: masthead or rail mount

Quote:
Originally Posted by foothillsailor View Post
Very interesting and informative thread---

Sorry for being dumb about this but I have a couple of basic questions about AIS:

1) if you use a splitter on your VHF antenna will you still be able to automatically hear and transmit on VHF while you are using your AIS or do you have to manually switch back and forth from AIS to VHF to AIS etc?

2) is it difficult to install a splitter, can it be installed next to your VHF radio set, and does it require any special programming ? I have a 55 ft mast and really at my age (72) I do NOT enjoy going up a 55 ft mast

3) what if you are also using your VHF antenna as a AM/FM radio antenna--will that be a problem?

4) Lastly any particular brand and model people can recommend for a AIS/VHF splitter --money isn't a real concern (within reason) but as it would be a DIY installation simplicity of installation is highly desirable (I am not particularly electronics savvy but can read instructions -for example I have successfully installed my own autopilot and wind, depth and speed instrumentation)

Thanks ahead of time for any help or advice
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G'day John,

Those are reasonable questions. My answers are based on my two installations, one an ICOM receiver with built in splitter, and my current one with a Vesper splitter. The Icom splitter claimed ~1 db insertion loss, the Vesper has a built in preamp and has zero uns.

1. Yes, your VHF functions continue normally. No operational changes are required.

2. In the case of the Vesper, it is a small black box with four connectors. One goes to the antenna, one to the VHF set, one to the AIS unit and one optional one to your AM/FM set. It also requires 12 volts. Connecting it up is pretty simple. In our case, it sits right next to the VHF set.

3. See above... not a problem.

4. I find the Vesper unit to be excellent, and the Vesper folks good to deal with. There may be other similar units available.

Sounds to me like your previous experience with installation should make this a piece of cake!

Cheers,

Jim
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Old 06-07-2015, 15:27   #36
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Re: AIS antenna: masthead or rail mount

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Originally Posted by S/V Alchemy View Post
Masthead. AIS can work farther either receiving or transceiving at the mast top than radar can at the spreaders and can give you a TCPA of huge ships you want to avoid (or to be seen by).

It is a great compleiment to radar in this way. Consider that if you are approaching land you can't yet see with radar, but you can see by AIS a pretty clear TSS in front of the land, you get more information than just a GPS lat/lon that tells you "you are 40 miles from shore". The AIS reveals that you are perhaps 25 miles from the sealanes. Those are things I want to know.
Wouldn't a chart show the sealanes?

Can you tell us what you do with traffic information 3-4 hours before you get to the sealanes? (assuming your vessel is doing 6-8kts) That is obviously a long time and lots of things change.
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Old 06-07-2015, 16:31   #37
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Re: AIS antenna: masthead or rail mount

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Originally Posted by Calypso52 View Post
Thanks all.... the consensus seems to be that higher is better but rail mount may be sufficient for starters at least. I couldn't seem to see a consensus on splitter or not. I suppose having a completely separate antenna (no splitter) is prudent in the unlikely event the main stick falls down.
I'm very much a novice with electronic gear, but I've had two AIS receivers. The first was the NASA connection to chart plotter and the instructions very specifically stated not to use a splitter. Ariel was on pushpit. I don't know why it said not to use a splitter, but I just followed the instructions. My second AIS is now incorporated in the Standard Horizon vhf radio which is on my main mast.

I will no doubt upgrade to a transponder though as they are getting cheaper. So, I'm guessing I'll then need to go back to a separate ariel. I'll probably do that when I eventually get to overhall my Mizen.
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Old 06-07-2015, 16:33   #38
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Re: AIS antenna: masthead or rail mount

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Originally Posted by hamburking View Post
There is an alternate solution not yet mentioned...give your masthead antenna over completely to AIS, then use handheld VHF. Cheap solution.
I'm not sure why you think this is an 'alternate' at all, let alone a cheap one. My hand held's have very little range, about 10 miles.
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Old 06-07-2015, 18:16   #39
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Re: AIS antenna: masthead or rail mount

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IMO, it's a waste of time making navigation decisions more than 10 minutes from TCPA. There are simple too many variables to use a AIS borne TCPA more than 10 minutes and then using that information to make changes to direction/speed.

If you are not confident to avoid a collision within 10 minutes, please keep the docklines on and don't venture out.

Point: rail mount AIS is all you need for collision avoidance. But, if you get off on seeing ships far away, certainly the top of mast will give you a much better range. But, choosing longer AIS at the determent of VHF comms* is completely foolish, again IMO.

*A buddy boat recently chided me for my rail mount AIS, he could only see me 8 miles out. Same friend then mentioned he could only hear my side of VHF comms when we were right next to each other. I had no problem carrying out VHF comms @ 20nm. He could not hear the other half but refuses to believe his antenna splitter has anything to do with it.

Using an X switch as MarkJ does is the best of all worlds, it allows you to manually switch between the 2 antennas.
With all due respect, AIS is to see and to BE SEEN. Speaking as a Cruise Ship Captain, I want to SEE everything out there as soon as possible with as much good data as to type of vessel, course and speed so that I can make navigation decisions as soon as possible. The writer seems to be concerned only with his needs not those of other vessels. AIS is an important safety tool for all mariners and the more information commercial vessels have on vessels operating nearby the better. The fewer unidentified "targets" on the radar screen the better. I cannot begin to tell you how frustrating it is to call a "target" on VHF 16 by giving Lat & Lon coordinates and not receive a response because the mariner in charge is not monitoring the radio or is not aware of his location to respond to my call for clarification of his intent. A change of course and speed 10 minutes from my desired minimum CPA is a big concern for commercial vessel operators.

So, the answer is mount the antenna HIGH and mount it securely. It may help save your life or someone else's.
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Old 06-07-2015, 19:45   #40
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Re: AIS antenna: masthead or rail mount

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With all due respect, AIS is to see and to BE SEEN. Speaking as a Cruise Ship Captain, I want to SEE everything out there as soon as possible with as much good data as to type of vessel, course and speed so that I can make navigation decisions as soon as possible. The writer seems to be concerned only with his needs not those of other vessels. AIS is an important safety tool for all mariners and the more information commercial vessels have on vessels operating nearby the better. The fewer unidentified "targets" on the radar screen the better. I cannot begin to tell you how frustrating it is to call a "target" on VHF 16 by giving Lat & Lon coordinates and not receive a response because the mariner in charge is not monitoring the radio or is not aware of his location to respond to my call for clarification of his intent. A change of course and speed 10 minutes from my desired minimum CPA is a big concern for commercial vessel operators.

So, the answer is mount the antenna HIGH and mount it securely. It may help save your life or someone else's.
If you believe my course corrections at 10 minutes will be detrimental to your desired CPA, no worries, if we ever cross paths, I'll let you handle all the collision avoidance course corrections, I'll stand on.

Not sure why you are referencing radar targets, AIS Class B with rail mounted antennas will be seen long before you see them on radar.
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Old 06-07-2015, 20:00   #41
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Re: AIS antenna: masthead or rail mount

Greater range is better. Ours is at 80 feet. We see class A at about 70 miles. In open ocean, the large guys may be running on auto-pilot with great circle rout correction. They may make auto-course corrections without regard to your class B and in fact, the bridge & watch may not be manned. I'd like to see the course change ASAP.
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Old 06-07-2015, 20:03   #42
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Re: AIS antenna: masthead or rail mount

I plugged my EM Trak into the laptop without connecting the antenna at all and turned it on. It, the EM Trak was inside the boat at the navstation and I received several targets as far as 21 miles away. I'm not saying that's an optimum install...Just saying like most things here there's no hard and fast answer.
I plugged in a rail mount antenna and saw the same targets. I plugged in the masthead VHF antenna and nothing changed.
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Old 06-07-2015, 21:05   #43
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Re: AIS antenna: masthead or rail mount

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Not sure why you are referencing radar targets, AIS Class B with rail mounted antennas will be seen long before you see them on radar.
Many if not most commercial vessels have ARPA and/or integrate the AIS signal with the radar targets thereby identifying those targets with vessel type, course and speed. This informs the bridge watch as to what actions may be necessary to maintain safe passage. Frankly many pleasure vessels can be unpredictable and radio calls or sound signals may be necessary to clarify intent. An AIS signal with vessel name is helpful when using the radio to confirm passing arrangements. If you take the time to monitor VHF 13 you will hear this procedure between commercial vessels almost always.
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Old 06-07-2015, 22:06   #44
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Re: AIS antenna: masthead or rail mount

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Many if not most commercial vessels have ARPA and/or integrate the AIS signal with the radar targets thereby identifying those targets with vessel type, course and speed. This informs the bridge watch as to what actions may be necessary to maintain safe passage. Frankly many pleasure vessels can be unpredictable and radio calls or sound signals may be necessary to clarify intent. An AIS signal with vessel name is helpful when using the radio to confirm passing arrangements. If you take the time to monitor VHF 13 you will hear this procedure between commercial vessels almost always.
As another professional mariner on a large ship, I couldn't agree more with this and your previous post. Our radars and ecdis unit are integrated with AIS so targets are AIS too if the vessel is equipped.

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Old 07-07-2015, 05:48   #45
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Re: AIS antenna: masthead or rail mount

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Many if not most commercial vessels have ARPA and/or integrate the AIS signal with the radar targets thereby identifying those targets with vessel type, course and speed. This informs the bridge watch as to what actions may be necessary to maintain safe passage. Frankly many pleasure vessels can be unpredictable and radio calls or sound signals may be necessary to clarify intent. An AIS signal with vessel name is helpful when using the radio to confirm passing arrangements. If you take the time to monitor VHF 13 you will hear this procedure between commercial vessels almost always.
But this thread is about where to mount an AIS transceiver antenna. I'm proposing that a rail mounted AIS antenna provides you visibility of that vessel before you'll acquire it as an ARPA target. The thread is not about non-AIS equipped boats.
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