AIS Transciever - Page 8 - SailNet Community
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post #71 of 136 Old 10-31-2019
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Re: AIS Transciever

AIS in navigation mode should only show targets in some reasonable range.

pay attention... someone's life depends on it
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post #72 of 136 Old 10-31-2019
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Re: AIS Transciever

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Originally Posted by SanderO View Post
AIS in navigation mode should only show targets in some reasonable range.
It does AIS is VHF technology. Range is similar to DSC Radio calls. The higher the antennas (receive and transmit) the greater the range. An antenna at kayak height would significantly less range than an antenna on a 60 ft mast.

Last edited by Arcb; 10-31-2019 at 06:28 PM.
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post #73 of 136 Old 10-31-2019
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Re: AIS Transciever

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Originally Posted by chef2sail View Post
Suppose on Saturday in July, 20% decided to turn them on. That’s 600 AIS signatures in a very confined area. It will look like a video game . The “ dangerous target” alarm sounding like a submarine klaxon every three seconds.
I have no dog in this fight, I don't care either way about AIS.

But the above nightmare scenario is just a software issue. The current interfaces assume a small number of targets, but if they become more common the interfaces will be updated to handle the larger number.
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post #74 of 136 Old 10-31-2019
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Re: AIS Transciever

We "broadcast" information already, in some awfully primitive ways: day shapes and lights. I'd say it's about time we begin broadcasting safety data at a 21st century level.

Often, you can't see them and virtually no one understands the this light stacked over that light, etc. Modern safety protocol doesn't require flip cards to try to remember. It just works.
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post #75 of 136 Old 11-04-2019
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Re: AIS Transciever

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Originally Posted by SanderO View Post
AIS in navigation mode should only show targets in some reasonable range.
Quote:
Originally Posted by Arcb View Post
It does AIS is VHF technology. Range is similar to DSC Radio calls. The higher the antennas (receive and transmit) the greater the range.
Except that AIS is a "mesh" network. The AIS contacts in range of you are rebroadcasting contacts that are more distant and out of reception range. So you don't really need a tall antenna to get long range contacts.

So being VHF technology doesn't limit contacts that it will show.

EDIT: see below, I am wrong!
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Last edited by TimMarks; 11-04-2019 at 08:46 PM.
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post #76 of 136 Old 11-04-2019
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Re: AIS Transciever

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Except that AIS is a "mesh" network. The AIS contacts in range of you are rebroadcasting contacts that are more distant and out of reception range. So you don't really need a tall antenna to get long range contacts.

So being VHF technology doesn't limit contacts that it will show.
You sure about that? Have a source that confirms that? My understanding is it is NOT meshed.
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post #77 of 136 Old 11-04-2019
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Re: AIS Transciever

Yeah, turns out I am wrong.

It is a mesh network in the way the transceivers work together, but there is no rebroadcast. So VHF range = on-hull contact display range.

I kind of assumed that "mesh" meant rebroadcasting. But it is just how the transceivers work together to time-share broadcast spaces.

Funny, because I swear that my AIS sees a lot further out than I would expect.
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post #78 of 136 Old 11-04-2019
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Re: AIS Transciever

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Originally Posted by MastUndSchotbruch View Post
You sure about that? Have a source that confirms that? My understanding is it is NOT meshed.
You are correct. For some reason, that false information got a life on the internet and has been impossible to eradicate. AIS is not a mesh network, and the data are not rebroadcast, except in rarer shore-based repeater systems around major commercial harbors. The satellite systems like MarineTraffic would not be considered a network.

Mark
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post #79 of 136 Old 11-04-2019
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Re: AIS Transciever

Oops, sorry Tim, we cross-posted.

If you are seeing large ships from a long distance, it is because their antennas are very high comparatively. If you are seeing buoys, it is because they are being transmitted from high shore-side antennas. We often see Miami harbor buoys in the Exumas Bahamas.

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post #80 of 136 Old 11-04-2019
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Re: AIS Transciever

Ive added and deleted marinetraffic a few times finding the delays in reporting to make it useless..for me.
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