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Old 02-05-2022, 16:32   #1
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How to test AIS output

I've got an Icom MXA-5000 AIS receiver, hooked to a Garmin GPSMap 5208.
I had to re-organize my nav station layout, but now can't seem to get AIS data delivered to the Garmin chartplotter.
Wondering if there is some way to test the output of the AIS unit to make sure it's actually outputting correct data on NMEA 0183?
It's very possible I just hooked it up wrong, but it would be nice to know if the unit is actually working before I start completely re-wiring it.

Thanks.

ps: I'll try to post a diagram of my wiring setup later tonight.
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Old 02-05-2022, 17:47   #2
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Re: How to test AIS output

I assume you have power to the unit.

You could find a USB to serial converter for a laptop and connect the PC out wires to it and watch the messages on a terminal program. You can also buy a NMEA 0183 to USB converter to be sure the actual NMEA connection is correct.

Another option is to get an analog multimeter and check the output. If there are messages you will see the needle bounce. You won’t know what they are saying but at least you can have some confidence that it is sending something.

Pin outs are in the manual.

However if it has power and no error lights, if there are any, it is probably a bad connection somewhere.
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Old 02-05-2022, 18:07   #3
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Re: How to test AIS output

Thanks for this. I have a digital multimeter, so will see if I get fluctuating readings indicating some sort of signal.
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Old 02-05-2022, 18:12   #4
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Re: How to test AIS output

I've attached a simplified wiring diagram below. I consulted the 0183 docs, and looks like AIS data is transferred on White - Orange&White.
I have a VHF also attached via 0183, and it is receiving valid GPS data from the plotter.
I've also tried switching the +/- wires on AIS, but still nothing showing.
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Old 02-05-2022, 18:26   #5
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Re: How to test AIS output

The NMEA standard is 4800 baud, but that is too slow for AIS data. The default used by nearly every AIS system is 38400 baud. On the Garmin in the Configure:Communications:NMEA 0183 Setup:Port Types you have to select NMEA HighSpeed for whatever port is connected to the AIS.

If that’s done the next easy thing is to swap the two data wires, there’s not really a standard as to which is data plus and data minus between talker and receiver (well, there is a standard but it is not well observed).

Those two are so simple I’d try them before breaking out the computer, a serial converter/port, and the software to check directly.

A multimeter is hard to use, particularly digital, the bit length at 38400 is 26 microseconds (even at 4800 it is only 2ms). Since talkers in NMEA tend to talk constantly you’ll generally just see the average between high and low.

[Edit] you posted as I was typing, wiring looks as expected. You’ve tried the swapping, would still check configuration. If that’s not right then might have to try swapping again once configuration is right.
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Old 02-05-2022, 20:51   #6
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Re: How to test AIS output

Most likely your problem is that the GPSMAP 5208 port that you connected to is not set for 38.4 kbps. This is simple to fix.

The ICOM MXA-5000 outputs NMEA 0183 at 38.4 kbps - as do most AIS units.

The GPSMAP 5208 has four NMEA 0183 ports, which likely are defaulted to 4800 bps (eight times slower).

Instructions from your Garmin 5208 manual page 105:

"Setting the Communication Format for Each NMEA 0183 Port"

1. From the Home Screen, select Configure > Communications > NMEA 0183 Setup > Port Types

2. Select the input port number you used for the AIS input.

3. Select the input format as "NMEA High Speed" (versus NMEA Standard).

You should have connected to the "DATA OUT" terminals on the ICOM (and not the PC DATA OUT).

Garmin's 5208 installation manual example for AIS has the ICOM + going to white and the - going to orange/white in the Garmin cable.

Only one input device can be on a port.

If those checks don't fix your problem, then the next thing to try is to reverse the input wires (white and orange/white) since determining + and - can be confusing (and sometimes inverted).

Garmin says your cable should be shielded with both ends grounded (although this is unlikely to cause the connection not to work at all).

And before this, you should check that the green power LED is lit on the top of the ICOM unit when it is fed 12 volts and the fuse is good.

And that you have a good antenna connection. Assuming you're passing the VHF connection through the ICON to your radio, then if the radio is picking up clear signals, the ICOM AIS would be also.

And last, but not least, there needs to be a transmitting vessel in range! My boat is still on the hard in Haverstraw, NY, and when I upgraded the software in my chart plotter last weekend there was indeed only a single tug transmitting on the Hudson river within AIS range - 30+ miles north of the City!
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Old 03-05-2022, 06:54   #7
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Re: How to test AIS output

What about checking with another AIS equipped boat in your area to see what information they are receiving from you? Wouldn't that confirm your system's installation?
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Old 03-05-2022, 07:56   #8
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Re: How to test AIS output

Not if it's just a receiver as the OP stated.
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Old 03-05-2022, 08:35   #9
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Re: How to test AIS output

Just looking at your wiring diagram for the first time. Your GPS wiring doesn't appear to make sense to me. It seems you've created a message loop.

There is no apparent reason that the ICOM should have a connection to the output of the Garmin for GPS. It would merge that Garmin data with the AIS data and resend it back to the Garmin unit. An apparent problematic loop.

The Garmin output (which contains the GPS messages) should go directly only to your VHF to support DSC transmissions.

There should be NO connection to the DATA IN connections on the ICOM and the pink and gray connections from the ICOM should be removed from the ICOM. The Garmin output should go directly to your VHF data input so the radio will have GPS data.

Again, make sure you've set the correct input port number on the Garmin to High Speed which represents the white and orange/white connections. The output port going to the VHF should still be at Standard Speed (4800 bps).

The ICOM manual is a bit confusing in this regard. It says "GPS receiver is connectable. When a GPS receiver is connected, the GPS information is added to the received AIS information, and can be sent to the connected PC or navigation system."

In your case, the GPS is ALREADY connected directly to the Garmin per your diagram via NMEA 2000. The ICOM has no need to have GPS data itself. This model does NOT transmit any AIS messages.

The ICOM feature of accepting an NMEA 0183 input at 4800 bps and merging this data into the AIS output stream can be useful for installations where it would free up a chart plotter input port for other devices. In your case, the GPS is being fed via NEMA 2000, so this feature is of no use. For boaters with an NMEA 0183 4800 bps GPS, however, this feature can be very helpful.

I have an ICOM MXA-5000 in my home which serves to feed both the AISHUB and Marine Traffic Web sites with NYC harbor AIS data over the internet. It's a nice reliable and affordable unit. On my boat, I have a Raymarine AIS 700 transceiver which just plugs into the NMEA 2000 bus (as SeaTalkng). Using NMEA 2000/SeaTalkng indeed makes device hookups much easier and quicker than NMEA 0183. There are no hidden speed settings, no issues with plus and minus signal connections, and a single connection takes care of both inputs and outputs. Great progress -- although, indeed, at some incremental hardware expense.
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Old 03-05-2022, 09:56   #10
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Re: How to test AIS output

@gmgershon
Thanks for the detailed reply. That did the trick; I had reset all 0183 ports to default. When I switched Port 1 to High Speed - nothing happened! But then I re-read your post, and switched the +/- wires, and now I'm showing a marina full of targets!

Thanks for the help.
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Old 03-05-2022, 09:58   #11
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Re: How to test AIS output

@PippaB,
Excellent - setting port to high speed, then swapping wires, solved the problem.
Thanks
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Old 03-05-2022, 10:04   #12
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Re: How to test AIS output

@GMGershon,
It was a little unclear whether the Icom needed GPS input. I wasn't aware that the AIS didn't need GPS to function.
So far, after your earlier suggested fix, the unit seems to be working. But I will try disconnecting the Data In wires later and see if it has any effect.

Thanks again.
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Old 03-05-2022, 16:58   #13
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Re: How to test AIS output

Quote:
Originally Posted by maclysaght View Post
I've got an Icom MXA-5000 AIS receiver, hooked to a Garmin GPSMap 5208. Wondering if there is some way to test the output of the AIS unit to make sure it's actually outputting correct data on NMEA 0183?
It's very possible I just hooked it up wrong, but it would be nice to know if the unit is actually working before I start completely re-wiring it. Thanks. ps: I'll try to post a diagram of my wiring setup later tonight.
I am in the process of installing four AIS Class A units on four different vessels for the same company. I have three done. The speed that these units communicate is called a baud rate. Click on the fastest.. 38,000 I believe. and you can check the output to and from the plotter and the AIS. The voltage is low, from 0 to 3 volts. Also if you installed a new antenna, check that the connection is properly made and soldered. If you unit starts and restarts and goes into a loop situation, the ground is not good enough. If and when the units are running it will show on your screen. Their is a time delay for the info to show up on the screen. Give it time, it is not instant. If you see BS and a number, it indicates a Base Station and not a vessel. A vessel will show up, a name of ship, vessel, the heading, and nautical miles from your position as a triangle point. On the chart plotter it will display the direction of that triangle, headding. By tapping your screen will display the name and info of the vessel. Also, If it does not show up on the GPS plotter, an update might be nessessary. Take you serial number and call Garmin... they are very helpfull and you can get the upgrades at no charge online. Let me know if I can help more... Good luck...
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Old 03-05-2022, 17:06   #14
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Re: How to test AIS output

Quote:
Originally Posted by Scrimshaw4 View Post
What about checking with another AIS equipped boat in your area to see what information they are receiving from you? Wouldn't that confirm your system's installation?
On a Class A AIS... yes another vessel can send you a signal and you will see it. We had two units working on each side of a dock and both were telling the other that they were too close. We have to program the parameters... distance off other vessels and I believe the depth alarm as per the chart plotter...
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Old 03-05-2022, 17:59   #15
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Re: How to test AIS output

@maclysaght,
@PippaB

Glad to hear your receiver is now working!

Yes, @PippaB was spot on when he and I were concurrently composing our responses - the port speed and reversed +/- signal connections are often the problem with NMEA 0183 hookups.

I can assure you that an AIS RECEIVER does NOT need GPS input in theory and practice. A TRANSMITTER does.

The received messages contain the location coordinates of the target vessels and your chart plotter calculates distance-to-target using its own GPS input connection - the AIS receiver doesn't do this calculation.

And in practice, my identical ICOM unit is sitting next to my workbench with no GPS and is faithfully sending AIS messages to the Web and displaying targets on an iPad via a Raspberry Pi!

OTOH, an AIS TRANSCEIVER/TRANSPONDER (a Class B AIS device) DOES need GPS input in order to transmit your vessel's location to other vessels.

If you eventually replace your AIS receiver with an AIS transceiver this is a consideration.

Almost all new Class B transceivers come with a GPS receiver built-in and you just need to install an (often included) GPS antenna. I think this is good since it does somewhat simplify installation, but more importantly reduces points of failure or outages for the AIS, which serves as an important modern vessel safety device.

My chart plotter has a good internal GPS receiver which is accessible to all devices on the NMEA 2000 network, but the separate GPS in my Class B AIS transceiver allows my boat to be seen even if there was an NMEA network problem, the chart plotter with the internal GPS failed, or the chart plotter was simply powered down at night while moored outside an anchorage area.

- Gary
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