View Full Version : What GPS to buy? Interface with VHF/ AIS

ronnie simpson
12-08-2011, 05:25 PM
I figure that this question is probably pretty relevant to a lot of people right now, as we prep for SHTP.

I am planning on going with the Standard Horizon Matrix VHF/ AIS combo. It's the roughly $300 VHF that is becoming very common.

My question is; what GPS' are people using that have the right NMEA output, to interface with the VHF/ AIS? I am looking for the lightest, cheapest, most simple fixed-mount GPS that I can get. I found a Garmin 128 GPS on ebay for like 80 bucks, but after reading all of the tech specs, I can't decipher if that thing will work with my VHF/ AIS. Does anyone have any insight on this topic? I'm hoping to spend less than $150 for the GPS.


Ronnie Simpson
Moore 24 "US 101"

12-09-2011, 11:24 AM
Hi Ronnie,

I have that same radio, and I am nearly certain the GPS you propose will work. I looked at the owners manual (http://static.garmincdn.com/pumac/82_OwnersManual.pdf). That GPS will put out NMEA sentences to the radio, and the radio will show the targets on the radio. I have the radio set up and working with both a Garmin GPS 12 which is a battery powered even more basic GPS and a Garmin GPSMAP 440s (2nd hand from Blue Pelican Marine). The nice thing about the fixed mount mapping GPS is the GPS will display the AIS targets. One more thing, if the GPS you are considering requires an external antenna to work, you will have to hook up the antenna. Some fixed mount GPS have optional external antenna, and at least in my boat, the GPS works fine without the optional external antenna.

Express 27 Thumper

12-09-2011, 12:03 PM
It does NMEA 0183, so it should work. I have one of these that came with the boat, but I took it out and don't use it. If you want it, PM me your address and I'll send it to you.

I had a 72 and 76cs handhelds which I put on a mount down below. They're wired into the 12V power and interfaced to the AIS, autopilot and speedo, and AIS+GPS data gets fed to the laptop chartplotter via NMEA 0183. Only downside of the handhelds is intermittent signal loss when crew or water gets between the unit and satellites (and I had to buy a separate mount and cable for them). You can probably pick up a 72 or eTrex for ~$50 now. I'm pretty sure every unit Garmin has made puts out NMEA 0183 at 4800 baud, which is what the gx2100 requires. Note that the AIS output will be at a higher 38400 baud. My AIS unit mixes in the GPS input and sends out AIS+GPS data at 38400 baud to the laptop. I'm not sure if the gx2100 does this. If you want to see AIS on your laptop, you might need two serial inputs, one at 4800 baud, one at 38400. But if you have AIS on the VHF, there's really no need for that.

The gx2100 seems like a really smart way to do AIS, hope it works out for you.

12-09-2011, 03:35 PM
Once upon a time, there were small boat sailors who raced to Pardise in Hanalei Bay using VHF radio communiction (relayed as necessary insofar as possible by some of us who were hams), sextant and paper chart navigation, no laminate sails, Walker logs, etc.
Amazingly, most of us made it there and had a great time meeting the challenges!
Having said that, I am grateful for the fancy electronics and such that make it possible for octogenarians to compete and pick up a trophy on occasion.

12-12-2011, 10:18 AM
Hi Ronnie,

I have the Standard Horizon radio Matrix AIS GX2100. It is pretty awesome, and the remote RAM mic is also pretty awesome. When hooked up to a GPS, you can see the AIS ship targets on the GPS chartplotter screen, the little display on the VHF radio itself and even on the little display on the RAM mic in the cockpit.

You can see my whole setup here


the AIS display on the mic looks like this :


The tricky part is that AIS uses a faster signal than ordinary NMEA, and lower-end GPS plotters may not have enough configurable ports to set it all up without a separate multiplexer. I also wanted to have the GPS data piped to my instruments.

I got the Lowrance GPS plotter because it fit into the existing space, and was compatible with the radar I (might) ultimately get. It wasn't too pricey, compared to a lot of stuff. But I am not that crazy about it, the map refresh rate is very very slow, and the user interface is not as easy as Garmin, and track export sucks. So I would stick with Garmin if at all possible. For a Moore 24, a lot of guys would have their plotter/radar display mounted on a swing-arm in the companionway, so they could swing it out to see it while sitting at the helm if the hatch was down. Or make a new hatch out of acrylic or with a window to see through, there's an idea.

You will have to read the Garmin manuals pretty closely to find the fine print about the configurability of NMEA ports on the plotter. After I bought my Standard Horizon AIS/VHF, I was at a loss about how to hook it up to my plotter. But Standard Horizon tech support was very helpful, they put me on to Brookhouse, a company in NZ that makes the multiplexer boxes that lets this stuff talk to each other. Depending on how much you want to do (i.e. plotter + AIS, or Plotter + AIS + instruments, or plotter + AIS + computer + instruments) you can maybe get away without buying a mux, which are like $360, more than the radio itself. I would go ahead and buy the radio, then tell Standard Horizon tech support exactly what you are trying to accomplish, and I would bet they have a list already of Garmin GPS's that have the features you want.

You can see my setup in Alameda some evening or weekend if you are interested --


Olson 34 Temerity

12-13-2011, 10:27 AM
The only problem is that the Standard Horizon radio/AIS is a bit of a current hog, over the weekend I measured it draws 600 mA in standby/receiving mode. That adds up to a lot of A-hr for a Moore 24. So you will be tempted only turn it on once in a while, or maybe when you sleep to take advantage of the AIS proximity/collision alarm. But perhaps you don't sleep? ;)

12-19-2011, 10:18 PM
Hi David,

Interesting network aboard Temerity. Does the standard matrix have a timed mode by chance that would allow you to do a minute of AIS scanning in a 4 minute window ? That would be a big power saver.

Also, does the matrix have a very rude audible alarm when a vessel is within a guard range or collosion course ?

I did a home brew AIS in long pac with scanner and ship plotter software. Sure is nice to have AIS along.


12-19-2011, 10:41 PM
I love having a multiplexer. For anyone struggling with integrating NMEA outputs with other devices, a short lesson on how NMEA works is a helpful step in solving the problem. I like Shipmodul. Simple, useful tutorial, and their product is easy to install, configure and use. You can even tell it to display all incoming NMEA sentences on your PC screen, very useful for diagnostics.


And I use this little device, which is especially cool because it has a USB output and converts SeaTalk. Ooo, just think of the possibilities. They have a Bluetooth version, too.



12-20-2011, 05:31 AM
Paul- do you have a Raymarine autopilot? if yes, is it set up to steer to magnetic courses only or for apparent wind angle, as well? If yes on the apparent wind angle option, do you have Raymarine wind instrument? The reason I ask, is I have read, and I would like to know if it is true, that Raymarine wind instrument speaking Seatalk works better with Raymarine autopilot than different wind instrument speaking NMEA with translation to Seatalk.

Brian- The radio does have an alarm, loud, than is adjustable to go off for either a closest point of approach (CPA) or time to closest point of approach (TCPA).


12-20-2011, 09:33 AM
Hi David,





I'm not sure about the timed mode. I would guess that the receiver uses the same amount of power as long as it is monitoring any one channel?? I can look this up in the manual. I've got the radio up and running, showing ships on the GPS plotter or computer, etc. but there are a lot of features I need to test. I tried making a DSC call the other day and didn't get through, I don't know how to do it right or maybe they ignored me. I will also check out the alarm feature.

However, I was out yesterday, and some guy accidentally triggered his DSC distress button, and my radio went apeshit with beeping alarms, etc. So that works! He did not have GPS enabled, but I think that in my setup I would be broadcasting my GPS coords. It is kind of tricky to test these things w/o pissing off USCG though. I really need to RTFM.

One thing I am looking into is using a VHF/DSC/GPS handheld like the SH HX851 as a MOB aid, the crew on deck wears one on the harness and if the crew goes overboard they can hit the DSC Distress button, and hopefully the MOB will appear on various other GPS/AIS displays.

The SH Matrix has a max display range of 15 nm. Targets beyond that are not plotted. However, I know that at sea you can see Class A ships out to over 100 nm, so the longer range signals are probably stripped out by firmware.

I looked at the ShipModul website, I would guess they are a better choice than Brookhouse, their unit seems more flexible. But Brookhouse was recommended to me by Standard Horizon tech support, so I started with them. The mux cost more than the radio though!

-- David

12-21-2011, 06:48 PM
...Raymarine autopilot? ...apparent wind angle? Raymarine wind instrument? ...wind instrument speaking NMEA with translation to Seatalk.

Hi Todd,

Actually the multiplexer converts SeaTalk to NMEA, but not NMEA to SeaTalk. So for example, you can connect several NMEA "Talkers" (outputs devices) plus your SeaTalk data wire pair to the multiplexer (it has 4 NMEA input ports, one of which can be substituted with SeaTalk), and it will combine all the data into 1 NMEA sentence, plus it will throw out any data that piles up in the buffer. Then it send the sentence to one or more NMEA "Listeners" (input devices), or it will send the aggregated NMEA sentence via USB to the PC.

But no, it won't take a NMEA wind instrument and convert it to SeaTalk for input to the Raymarine autopilot.

So to answer your questions:
Yes, Raymarine X-5 autopilot
Yes, apparent wind angle mode
Yes, Raymarine wind instrument
Raymarine displays
Using SeaTalk between all Raymarine devices
Also sending all SeaTalk data to the muliplexer input
Sending NMEA from my Garmin GPS to the NMEA input on the course computer AND to a Multiplexer NMEA input
AIS NMEA data goes to a Multiplexer NMEA input
Multiplexer NMEA out includes everything, and that goes to my PC via a USB port
Raymarine displays show all GPS data and SeaTalk instrument data, very nicely
All GPS-related autopilot functions work okay, but not perfectly

Here's the hitch... the autopilot will steer to a waypoint, and the displays will show the waypoint data only when I've activated an actual "route" on the Garmin device. If I use the "goto waypoint" function on the Garmin unit, apparently Raymarine doesn't know what to do with the NMEA data and the autopilot won't steer to the waypoint, and the displays show no waypoint data. It's a minor bother, and it's workable.

I have no direct experience on whether the autopilot would work well with NMEA wind data. There are 2 NMEA input ports on the course computer, and as I noted, I use one of them to get the GPS data into it. So you could try sending wind data to that. But I suspect it won't work well. This is a good question for the Raymarine tech folks, who are very helpful and knowledgeable. I suspect it would need more than basic NMEA data, and I suspect it relies on specific timing of data.