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Old 21-06-2013, 12:06   #46
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Re: considering an ais transponder, any recommendations?

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Originally Posted by jeremiason View Post
The distances were easy since they were displayed when they lost my signal, but since they were traveling at 15 knots and my stationary boat was transmitting every 30 seconds I added a fudge factor of a mile. They reported losing my signal at 11 miles on the taller antenna.
IIRC, a Class B moving <2kts only transmits dynamic data every 3 minutes, not 30 seconds.
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Old 21-06-2013, 12:07   #47
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Re: considering an ais transponder, any recommendations?

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A networked antenna is one that acts as the antenna for and provides data to every component in the network. The Simrad NAIS 400 and the identical Lowrance/ B & G units cannot accept signal from any such antenna.

As for " I never mentioned this " try your post 24

" Also note that Raymarine is only compatible with C/E wide series only and requires the latest software. "
I presume you mean a networked GPS. every GPS has an antenna, there is no such thing as a "networked antenna".

To my knowledge no AIS used N2K supplied GPS feeds to work, because thats against the specific recommendations of the IMO. N2K is connected to AIS to allow the AIS to feed dynamic and static AIS data via PGNS to all devices on the network.

The main reason that so many issues arose with AIS and N2K , is that NMEA took ages to define the relevant AIS PGNs and manufacturers either didnt add n2K support or added proprietary PGN support ( Ray,Garmin, Simrad and others) in order to bring class B transceivers to the market.

Now that such PGNs have been defined, manufacturers have been updating software in both MFDs and AIS units to use the NMEA standard PGNS, I beleive Ray, Garmin and SIMRAD have all done so , certainly according to the most recent software updates Ive seen.

As to my comment re Ray C and E series, all I was mentioning was that Ray decided not to upgrade older C and E series to handle N2K AIS ( but even that I would need to verify as it could have changed).

SO , SAvoir, I still dont see the point you are trying to make with teh "networked antenna"

dave
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Old 21-06-2013, 12:55   #48
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Re: considering an ais transponder, any recommendations?

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Originally Posted by jeremiason View Post
Just FYI - AIS Class B transmits at 2 watts, not 3...

Yes, you are correct that many things effect VHF transmissions, but what I was trying to relate was that testing my AIS Class B Unit on two different antennas got very different results, with higher antenna producing a significantly longer range.

No, it wasn't a scientific test, it was me calling a couple buddies of mine who were operating tourist ferries on San Francisco Bay while I was parked at the dock. They were able to see my AIS signal on there receivers while they drove towards the GG Bridge.

The distances were easy since they were displayed when they lost my signal, but since they were traveling at 15 knots and my stationary boat was transmitting every 30 seconds I added a fudge factor of a mile. They reported losing my signal at 11 miles on the taller antenna.
Oops! You're right about the Class-B transmit power. I mis-remembered it.

Actually, now that you describe it, your testing seems pretty solid. Normally we "test" this stuff using targets of opportunity, and the random "can you see me now?" VHF hail. In any case, your results seem quite plausible, and are in accord with my own less-rigorous tests.
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Old 21-06-2013, 13:02   #49
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Re: considering an ais transponder, any recommendations?

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IIRC, a Class B moving <2kts only transmits dynamic data every 3 minutes, not 30 seconds.
True, and a good point! Tom, how did you deal with the slow transmit rate?
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Old 21-06-2013, 16:17   #50
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Re: considering an ais transponder, any recommendations?

Eric, they seem to have gone off on a tangent and stopped answering your question. I think you can't go wrong with the Vesper unit. I am in a similar boat with you.

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I'm hoping to use a splitter, and that the GX2150 will be smart enough to know (via the same MMSI) that "my boat" is not another contact.
Where do you get this hope from? I have the SH 2150 and am planning to add a Vesper or RM AIS transceiver. For redundancy, I was planning to use the SH AIS data for the PC and the Vesper/RM unit for the RM chartplotters. However, SH tells me that the AIS detection cannot be turned off and I do not believe it can distinguish and not display a signal from the same MMSI (if you have backup, pls let me know). Since I don't want to have the SH (and PC) show my own boat about 30' away and deal with collision alarms and ignore features, etc., I am planning to use the Vesper/RM unit for data to all devices and keep the SH as backup. The radio will show me on its little screen, but I don't care about that. The Vesper/RM AIS will have a dedicated antenna on the davits.
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Old 21-06-2013, 17:08   #51
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Re: considering an ais transponder, any recommendations?

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Eric, they seem to have gone off on a tangent and stopped answering your question. I think you can't go wrong with the Vesper unit. I am in a similar boat with you.



Where do you get this hope from? I have the SH 2150 and am planning to add a Vesper or RM AIS transceiver. For redundancy, I was planning to use the SH AIS data for the PC and the Vesper/RM unit for the RM chartplotters. However, SH tells me that the AIS detection cannot be turned off and I do not believe it can distinguish and not display a signal from the same MMSI (if you have backup, pls let me know). Since I don't want to have the SH (and PC) show my own boat about 30' away and deal with collision alarms and ignore features, etc., I am planning to use the Vesper/RM unit for data to all devices and keep the SH as backup. The radio will show me on its little screen, but I don't care about that. The Vesper/RM AIS will have a dedicated antenna on the davits.
I can verify that the 2150 is smart enough to recognize transmissions with it's own MMSI number. It won't display your own boat. Assuming you have the same MMSI number programmed into both units.
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Old 22-06-2013, 10:05   #52
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I can verify that the 2150 is smart enough to recognize transmissions with it's own MMSI number. It won't display your own boat. Assuming you have the same MMSI number programmed into both units.
Cool. Thx for confirming that. Did I understand from previous poster that the manufacturer didn't know that? That would be a serious technical flaw really.

I think ill install on the arch until I pull the stick one day. I understand the argument that it is generally unnecessary to see that far out, but Ive never complained about having MORE time to handle traffic. I presume most units allow you to use settings to clean up the display?

Having another VHF antenna on the mast adds some redundancy for comms in case the radio antenna goes out.
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Old 22-06-2013, 12:28   #53
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Re: considering an ais transponder, any recommendations?

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Cool. Thx for confirming that. Did I understand from previous poster that the manufacturer didn't know that? That would be a serious technical flaw really.
I interpreted him as saying you cannot turn off the AIS reception in the SH, which sounds reasonable.

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I think ill install on the arch until I pull the stick one day. I understand the argument that it is generally unnecessary to see that far out, but Ive never complained about having MORE time to handle traffic.
What is there to 'handle' with a vessel 25nm off your starboard beam? (gee, I better check on that guy in an hour to see if he is any closer!) Again, I see Class A's minimum 8-10nm and Class B's minimum 4-6nm. For me, that is enough time, and best bang for the buck on the installation. YMMV

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I presume most units allow you to use settings to clean up the display?
Let's hope so, although I'm generally pretty disappointed in the quality of software in the marine space. I can filter based on distance and speed. (don't show vessels further away than ?nm, and/or slower than ?kts)

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Having another VHF antenna on the mast adds some redundancy for comms in case the radio antenna goes out.
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Old 22-06-2013, 13:18   #54
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Re: considering an ais transponder, any recommendations?

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Originally Posted by cheoah View Post
Cool. Thx for confirming that. Did I understand from previous poster that the manufacturer didn't know that? That would be a serious technical flaw really.
Just to be clear, the manufacturer commented the same several months back.

Adding a Transponder to my GX2150


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Rebel Heart,

As long as you use the same MMSI you should not experience any issue.

Best regards,

Happy New Year!

Jason Kennedy
Standard Horizon
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Old 22-06-2013, 14:24   #55
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Re: considering an ais transponder, any recommendations?

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Originally Posted by DotDun View Post
What is there to 'handle' with a vessel 25nm off your starboard beam? (gee, I better check on that guy in an hour to see if he is any closer!) Again, I see Class A's minimum 8-10nm and Class B's minimum 4-6nm. For me, that is enough time, and best bang for the buck on the installation. YMMV
DotDun:

I see your point of AIS clutter in the Bays and Harbors, but offshore the greater the transmitting distance, the earlier the OTHER vessel will see you.

During our cruising, I frequently saw large cargo and passenger ships alter there course around me. Not because they had too, but because they saw me early enough to do it.

At 10 miles away, a large ship altering course just 1 or 2 degrees will open several miles by the time we are at the CPA.
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Old 22-06-2013, 20:16   #56
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Re: considering an ais transponder, any recommendations?

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DotDun:

I see your point of AIS clutter in the Bays and Harbors, but offshore the greater the transmitting distance, the earlier the OTHER vessel will see you.

During our cruising, I frequently saw large cargo and passenger ships alter there course around me. Not because they had too, but because they saw me early enough to do it.

At 10 miles away, a large ship altering course just 1 or 2 degrees will open several miles by the time we are at the CPA.
I to have witnessed a vessel altering course, but not at 10 miles away. You have witnessed such at that distance?
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Old 22-06-2013, 20:49   #57
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I to have witnessed a vessel altering course, but not at 10 miles away. You have witnessed such at that distance?
Offshore I've watched them alter course certainly before they appear over the horizon, that's from them picking me up on radar. Not lots and lots but then seeing anything offshore is a rarity.
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Old 23-06-2013, 04:46   #58
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Re: considering an ais transponder, any recommendations?

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I to have witnessed a vessel altering course, but not at 10 miles away. You have witnessed such at that distance?
Yes I have a few times, twice I think. It does seem a long way off to direvert!



I am quite sure that some shipping lines have set rules about CPA and if the CPA is less than one mile they do all sorts of things to increase it, even though still a long way off.
Often I have heard VHF conversations where one captain asks for a CPA of one mile. Often I see the CPA at exactly 2 miles too, so some companies may like 2nms.
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Old 23-06-2013, 04:52   #59
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Re: considering an ais transponder, any recommendations?

In this screenshot in Florida Straits 3 ships are diverting at the same time for Lil' 'Ol Me!


Note the Range Ring is set at 10 NMs. The was NO VHF consultation either! They just did the diverting without chat.

In the one below it shows the value of AIS in a busy harbour!
Boats appear to the tired old skipper as coming from EVERYWHERE!!!!!!!
But a look at the AIS tracks show they are really on routes of their own and can be avaoided. One can even find a route all the way up this (well known ) waterway without bumping into anything much at all.

Hows that for good use of AIS?!
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Old 23-06-2013, 05:10   #60
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Re: considering an ais transponder, any recommendations?

same happened to me yesterday, CPA was a bit over half a mile but he diverted about 10 degrees to make it a mile. He changed course about 3 miles from me. Better to change course ASAP as it doesn't increase their route much. Iwas happy enough with half a mile in the conditions though.
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