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Old 13-07-2015, 01:19   #16
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Re: Starting from scratch

Wow. Having been in electronics and programming all my life I can say I feel your pain and frustration. And of course it then makes me wonder how to proceed. You obviously have much more money than I. I will not be doing the level of redundancy you are attempting but it sounds as if the individual items you are working with just don't work anyway.
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Old 13-07-2015, 02:23   #17
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Re: Starting from scratch

I do PC based systems Basic PC draws 10w. You can use any monitor you want, or one of ours. Have a look at PC Based Yacht Systems Boating Gear fit for the King Sorry but there is a database issue on my site right now, we are working on it. You can see the basics though, and I'm happy to answer any questions. matt@neptunes-gear.com. I have one of these on my own boat, with repeater screens in the cockpit and wifi to tablets/phones.
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Old 13-07-2015, 04:24   #18
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Re: Starting from scratch

Hi Matt. How does your 12v pc, plus monitor compare in real life power consumption to a small laptop? I can definitely see the benfits of a small fixed unit in terms of, dampness and space. We used one on the 60 footer I sailed in Antarctica, with a cheap silicon keyboard. Worked great and freed up lots of space on the chart table. Wet hands were not an issue.

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Old 13-07-2015, 07:58   #19
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Re: Starting from scratch

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Originally Posted by jwcolby54 View Post
Wow. Having been in electronics and programming all my life I can say I feel your pain and frustration. And of course it then makes me wonder how to proceed. You obviously have much more money than I. I will not be doing the level of redundancy you are attempting but it sounds as if the individual items you are working with just don't work anyway.
I too spent my career designing, building, selling, servicing electronics products. That's probably why I feel compelled to dig into each issue that I see.

I bring up redundancy only because that's when some of the problems turn up. But not all of them. The NavPilot, for example, sends periodic broadcast requests for the Humidity PGN. Why it needs to know the humidity is beyond me, so I presume that's a bug in and of itself. But these broadcast requests require every device to stop and reply either with the PGN or with a NACK resulting in a mini traffic storm. If you have enough devices on the network, it really starts to add up. Also, on power up, it sends out a PGN using a different and illegal source address. Different devices respond differently to the appearance of this illegal PGN. It used to cause address claim storms which are highly disruptive, but Rose Point put in some defensive code to stop it. Go Rose Point! These are just some examples of issues that show up even without any redundancy.

Where I think I'm probably going to end up is with most if not all of the nav equipment on 0183, and just the Maretron monitoring gear on N2K. I'll still have a converter or two, but they work much better going from 0183 to N2K than in the other direction, mostly because none of them can do source selection of N2K devices.
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Old 13-07-2015, 08:17   #20
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Re: Starting from scratch

Put your VHF antenna at the top of the mast, and use a splitter for the Vesper AIS. That way your VHF and AIS transpond will be at maximum distance. I didn't see the splitter on your list.
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Old 13-07-2015, 09:35   #21
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Re: Starting from scratch

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Put your VHF antenna at the top of the mast, and use a splitter for the Vesper AIS. That way your VHF and AIS transpond will be at maximum distance. I didn't see the splitter on your list.
I kind of wanted to use separate antennas for the VHF and transponder. My reading indicates that the splitter is an intelligent device that electronically switches the antenna between the two devices. When the VHF is being used, the transponder cannot get at the antenna and vv.

If I use a dedicated 6' Whip for the transponder, even if mounted on a rail on deck, it will still be seen 5-10 miles away. AFAICT the biggest use for the transponder is to tell other boats where I am for collision avoidance. They don't need to see me 30 miles away to avoid colliding with me.

My VHF will have AIS collision stuff in it so I will still see others (with AIS transponders) and get collision alarms etc. using the VHF AIS.
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Old 13-07-2015, 09:40   #22
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Re: Starting from scratch

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I kind of wanted to use separate antennas for the VHF and transponder. My reading indicates that the splitter is an intelligent device that electronically switches the antenna between the two devices. When the VHF is being used, the transponder cannot get at the antenna and vv.

I think that is right, except for the vv (vice-versa). I think the VHF transmit takes priority over the AIS transmit.

In an emergency scenario offshore, it might be nice to both see (AIS) and hail (VHF) ships that are far away. By name.
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Old 13-07-2015, 09:53   #23
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Re: Starting from scratch

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Originally Posted by sailjumanji View Post
I think that is right, except for the vv (vice-versa). I think the VHF transmit takes priority over the AIS transmit.
So the switch just cuts away in the middle of the AIS transmission by the transponder? I doubt that. However the messages transmitted are just short strings of data (a handful of bytes AFAICT) so the total wait to get at the antenna for the VHF would probably be milliseconds.

The other way around not so much. Get a chatty person keying the mike for 10 minutes and the AIS transmission doesn't go out.

Quote:
In an emergency scenario offshore, it might be nice to both see (AIS) and hail (VHF) ships that are far away. By name.
Yes, but the transponder is not necessarily about my seeing anything, it is (mostly) about others seeing me. I CAN "see" other transponders using my VHF AIS receiver, which of course comes from "up the mast" if my VHF antenna is in fact "up the mast". Theoretically that VHF data can be sent to my chart plotter. AFAICT the transponder does in fact "see" and can send whatever it sees to the chart plotter. I assume that I would have to tell the chart plotter which AIS stream to use.

And the "hailing" part is via my VHF radio which is "up the mast".
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Old 13-07-2015, 10:02   #24
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Re: Starting from scratch

Ok, I think I had the transmission priority right. It's VHF, and then AIS. At least for the Vesper splitter I am using. From their website:

VHF-in-use indicator appears on the screen of the AISWatchMate 850 and WatchMate Vision AIS transponders whenever the VHF radio is being used. This unique feature indicates when AIS traffic is delayed due to the antenna being in-use by the VHF radio and is also an excellent indicator if a stuck-mic condition exists.
Fail-safe VHF priority

VHF radio always has priority and the VHF can always transmit even if the power to the splitter fails.

Regarding the need to see them, yeah, I had that mixed up, thinking the antenna location was going to be swapped.
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Old 13-07-2015, 10:08   #25
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Re: Starting from scratch

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Originally Posted by jwcolby54 View Post
I am buying a boat with no electronics worth keeping.

My objectives are:

1) Have electronics which can be used standalone, but which also integrate. 2) Have the N2K backbone, short, and inside at nav station.
3) Have modules cabled directly to the short backbone such that all connections are at the nav station. Single point of failure is preferable to possible points of failure all over God's green earth (the boat). Make the Nav station the focal point.
4) Redundancy wherever possible.
5) Have displays at nav station and tablets using wifi.
6) Allow system not locked in to a single manufacturer.

So my thoughts:

1) Standardize on N2K
2) Standardize on OpenCPN run on a PC
3) New PC - All in one Dell or HP, 19" or 24".
4) Existing Android (Samsung) pads as backup displays.
5) Actisense NGT1 N2K - USB. PC to N2K interface.
6) N2K Backbone
7) Vesper Marine XB-8000 AIS transponder - Provides GPS 1 data (primary). Provides AIS 1 data (primary).
8) Standard Horizon GX2200 MATRIX VHF/AIS/GPS - Provides GPS 2 data (backup). Provides AIS 2 data (backup). Provides DSC (primary)Yea I know, not N2K But everything else!
9) Standard STD-CMP30B RAM3 remote control mike for the cockpit
10) Standard Horizon HX870 hand held. Provides GPS 3 data (backup). Provides DSC (backup)

That covers the basics AFAICT.

Assuming the previous:

1) Mount the XB-8000 at Nav station with a separate antenna mounted on the bow. This avoids the antenna mux stuff as well as "one or the other itis". Use the built-in wifi to get the data to/from the nav station. Cable to N2K backbone for redundancy.
2) Mount the GX2200 at the nav station with the antenna up the mast (if possible) or on the aft rail - to provide physical separation between VHF radio and AIS transponder.
3) Mount the PC in the nav station with a usb / serial interface to the GX2200.
4) Wire up a basic N2K backbone at the nav station. So far not used. Interface to sensors.

Here is where my research breaks down. I have not yet found N2K compatible sensors, though I am sure they are out there.

Add N2K wind speed / weather station stuff.
Add N2K Sonar.

I have heard bad things about through hull water speed and temp sensors (sea life attachment).

OK so now it is time for your thoughts.
I did the exact same thing, rewired the entire boat from scratch with an N2K backbone and mode B AIS, radar, sonar/wind sensors etc.

Tiring, long process but worth it. And N2K actually rules. I went with Simrad stuff with the exception of the AIS (Digital yachts).

I would use two antennas, not a splitter. I have my VHF on my masthead and my AIS one on a spreader. An added bonus is if one gets trashed, I can easily move my VHF to the AIS one and vice versa.
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Old 13-07-2015, 10:10   #26
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Re: Starting from scratch

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I would use two antennas, not a splitter. I have my VHF on my masthead and my AIS one on a spreader. An added bonus is if one gets trashed, I can easily move my VHF to the AIS one and vice versa.
Oh, very nice. Got your redundancy, and better range for AIS vs deck or arch mounted.
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Old 13-07-2015, 10:11   #27
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Re: Starting from scratch

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Originally Posted by sailjumanji View Post
Ok, I think I had the transmission priority right. It's VHF, and then AIS. At least for the Vesper splitter I am using. From their website:

VHF-in-use indicator appears on the screen of the AISWatchMate 850 and WatchMate Vision AIS transponders whenever the VHF radio is being used. This unique feature indicates when AIS traffic is delayed due to the antenna being in-use by the VHF radio and is also an excellent indicator if a stuck-mic condition exists.
Fail-safe VHF priority

VHF radio always has priority and the VHF can always transmit even if the power to the splitter fails.

Regarding the need to see them, yeah, I had that mixed up, thinking the antenna location was going to be swapped.
Yep. Notice though that the "VHF Priority" thing specifically says that in the case of "stuck mike" the AIS transponder never gets the antenna. Stuck mike can be a literal "stuck mike" or it might be a chatty person simply keying the mike for 10 minutes. In either case the transponder never gets the antenna.

And it says that should the power fail to the antenna switch, THEN the VHF gets the priority (and the transponder never gets the antenna).

Both of these things are what drives my decision to use separate antennas.
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Old 13-07-2015, 10:16   #28
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Re: Starting from scratch

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I would use two antennas, not a splitter. I have my VHF on my masthead and my AIS one on a spreader. An added bonus is if one gets trashed, I can easily move my VHF to the AIS one and vice versa.
From my reading that works well. The location on the spreader provides vertical separation from the VHF antenna. The only real issue is the deformed radiation pattern due to the proximity of guy wires and the mast, something that really should be tested somehow. Not sure how.
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Old 13-07-2015, 12:17   #29
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Re: Starting from scratch

The core problem with N2K is the limited bandwidth (it's only 265Kbps) being exacerbated by "blind senders" which stomp on the bus instead of waiting for silence, thereby talking over the reports of other units.

Ultimately yes, it's bad software design by vendors and bugs causing transmission storms.

The "right" way to solve the problem is with N2K bridges to isolate bad talkers, but just figuring out who those bad talkers are is problematic. Ultimately the real solution will be the same as it was for Ethernet: True fire-walling switches (multi-port bridges) that can isolate traffic and eliminate overzealous reports from chatty talkers, and prioritize important traffic such as information needed for auto-piloting, depth sounders, etc. The switch would simply replace the major backbone.

The CAN bus used by NMEA2000 is the same as J1939 for Semi-trucks and their trailers, but running at half the speed. The PHY layer chipset is $2 in quantity. No reason why someone couldn't build a device that solved all these problems using off-the-shelf components. A simple ARM-based logging device with an "access list" that prevented unnecessary blind senders from storming the bus would solve most if not all problems.
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Old 13-07-2015, 12:22   #30
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Re: Starting from scratch

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Hi Matt. How does your 12v pc, plus monitor compare in real life power consumption to a small laptop? I can definitely see the benfits of a small fixed unit in terms of, dampness and space. We used one on the 60 footer I sailed in Antarctica, with a cheap silicon keyboard. Worked great and freed up lots of space on the chart table. Wet hands were not an issue.

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Depends on how you build the PC. Processors can vary quite a bit, and so do HDDs. Mine was 25 watts but build for low power using a older system-on-a-chip from a taiwanese mfr. The hard drives take most of the power.

If you could find a laptop that ran on 12VDC it would be idea, but they're all up around 18..22 volts for battery charging.
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