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Old 04-09-2016, 02:41 PM   #1
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AIS transponder GPS strength

I am considering replacing my AIS receiver with a transponder. It is equipped with a built in GPS but also has a port for an external GPS. I want to switch it out with my receiver that is located in the pilothouse next to the onboard PC. It is basically inside a cabinet behind the helm. In your experiences, do you think I would need to add an external GPS, or is the internal GPS generally powerful enough for reporting my AIS position? Thanks
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Old 04-11-2016, 09:54 AM   #2
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"It is equipped with a built in GPS" must be the contemplated transceiver, right? And you're wondering if it will receive position from a cabinet "behind the helm" - you mean forward of the helm?

I'd guess it would be 50/50. I'm under cover in my slip, and my GPS (which feeds my AIS) is located on my pilothouse roof. When I come back to my boat after a week I see radial track positions going out a half-mile in random directions. I sometimes get a notice from Marine Traffic saying my boat is located in the middle of the nearby city and proceeding at 10 knots towards Canada.

If you could mount the transceiver near the ceiling of your pilothouse you would get better results.
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Old 04-11-2016, 12:57 PM   #3
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You can never have too many GPS.
How many do you have now?

I would add an external one. I did and now I have one each for:
Raymarine Chartplotter,
Digital Yacht AIS Transceiver
Maretron system which then supplies data to ComNav Autopilot and Coastal Explorer
VHF radio

Also, I also have three GPS pucks for laptop (they are $28 each from Amazon).

Yes, I know, when the North Koreans detonate the EP bomb none of them will work.

So I ought that plastic Davis Sextant. At least I will know what hemisphere I am in.
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Old 04-11-2016, 01:15 PM   #4
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I have one GPS on the radar mast and a puck for backup. I suppose it would be a good idea to have a second on the mast.
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Old 04-11-2016, 02:02 PM   #5
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Brand and model of the AIS is?
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Old 04-11-2016, 02:12 PM   #6
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The transceiver I am considering is the Si-tex Metadata Class B transceiver. I currently have the Si-tex receiver only and would prefer to switch out the models, keeping it in the same location in the cabinet forward of the helm.
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Old 04-11-2016, 02:57 PM   #7
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"It is basically inside a cabinet behind the helm. In your experiences, do you think I would need to add an external GPS, or is the internal GPS generally powerful enough for reporting my AIS position? Thanks"


I have the Digital Yacht Class B mounted at the com center where I can easily monitor the lights. Being able to see the lights proved helpful because the unit would go into status red mode which according to the instructions meant I was not broadcasting position/course/speed. The AIS target displays on the chartplotter continued to function normally. If it had been mounted in a cabinet I would have never noticed the status lights or the need for repair. Food for thought.


Also, I am probably reading this wrong but you ask if the internal GPS is powerful enough to report your position? On a transponder the GPS reports only to the AIS which in turn broadcasts the position via VHF (or at least close to VHF) to stations close enough (VHF range) to receive this signal through a dedicated antenna or signal splitter shared with an existing VHF radio.


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Old 04-11-2016, 05:13 PM   #8
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Quote:
Originally Posted by steelydon View Post
I have the Digital Yacht Class B mounted at the com center where I can easily monitor the lights. Being able to see the lights proved helpful because the unit would go into status red mode which according to the instructions meant I was not broadcasting position/course/speed. The AIS target displays on the chartplotter continued to function normally. If it had been mounted in a cabinet I would have never noticed the status lights or the need for repair. Food for thought.
I had the same situation - except I wasn't checking the lights and I only noticed when I stopped appearing on Marine Traffic (which only registers if you're in a populated area). And some of the members on this forum have whinged about boats that are docked appearing as possible collisions on their AIS console / app with primitive target detection and have asserted that everyone should turn their AIS transmission off when at the dock (there's usually a button on the front to control this).
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Old 04-11-2016, 05:45 PM   #9
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rule of thumb. Metal and wood attenuate gps signals, plastic (fiberglass) and glass does not.

Metal is intuitive wood however isnt, but it only takes a couple cm's of wood before the signal is dead.
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