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While redesigning my navigation system, I realized that I wanted several instruments to share information with my chartplotter, while also being able to share information between themselves. In addition, I also wanted a PC to be able to receive information from these instruments.

After some investigation, I found a whole product line of NMEA multiplexers from Shipmodul.  I chose the MiniPlex-42BT.  This version allows for 4 “talkers”, compatibility for SeaTalk and AIS, several “listeners” depending on your configuration, and Bluetooth support for your computer.

My goal was to connect my Tacktick NMEA interface, autopilot, chartplotter, AIS receiver, VHF radio, and my PC all to the same system.  After a lot of trial and error, and using MPXConfig from Shipmodul which allowed me to see the exact traffic passing through my multiplexer, I ended up with a slightly modified configuration.

Most notably, I was unable to connect my AIS receiver to the multiplexer – not because it wouldn’t work, but because it sent so much data out so fast, that it caused “overflows” – where data from the slower NMEA 0183 instruments was being dropped in favor of the AIS data.  Although AIS is nice information, I would rather have my chartplotter talking to my autopilot than know what’s around me.

Final configuration was to have the chartplotter, VHF radio, and Tacktick NMEA interface all connected as “talkers” so that other instruments could see their data.  The chartplotter, VHF radio, Tacktick NMEA, and autopilot were also “listeners” chained off of one port of the multiplexer.  The AIS system was directly connected to my chartplotter over a NMEA 0183 high speed port.   My PC used Bluetooth to see all of this data, and also transmit waypoints and routes if needed.

The only disadvantage to this system is the fact that the AIS data is not visible on my PC, which is running Rose Point Navigation’s Coastal Explorer software, which supports AIS.  I don’t use my PC while underway, but it would be nice to see things at anchor or when planning a short trip.

By far one of the most useful utilities when building this configuration was the MPXConfig utility available for download from Shipmodul.  If you purchase one of the newer AIS/Bluetooth units, you will need to download a newer version of the utility from the link above, as the one included on the shipped CD does not allow you to toggle AIS.

When setting the unit up, you have a number of options – Server, Hub, AIS, and Auto.  I chose Hub mode because I wanted everything that came in all talker ports to be repeated out the listener ports.  By default the system comes setup as Auto mode, which will toggle between these.  One of the things I wanted to work all of the time was for the autopilot to receive wind angle data and waypoint information (if a course was set) regardless of what else was going on.  Leaving the system in Auto or Server mode would have possibly caused some of the messages coming through to be dropped in the event that another instrument got chatty.  Hence the reason for choosing Hub mode.

However, when using Hub mode, you have to be careful.  NMEA 0183 is limited to 4800 bits per second, which is pretty slow.  With the Tacktick NMEA interface transmitting wind, compass, and fast heading information, along with the chartplotter and VHF.  With the default configuration on my chartplotter, I ended up having a lot of overflows – where data is dropped from one talker because there’s too much going on.

After examining Garmin’s configuration reference, and reading about NMEA sentences and which ones meant what, I chose to disable some of the Garmin proprietary sentences to slow down the amount of data going to the multiplexer.  This ended up solving my overflow problem.

Overall I have been very happy with the multiplexer.  Being able to connect to it via Bluetooth is very convenient, and helpful for planning trips and reviewing data.  Having all of the instruments connected together makes things so much easier to use.  Now my wireless Tacktick instruments display waypoints, XTE and other useful information when a course is set, and the autopilot steers towards it correctly, all while the chartplotter is getting depth, speed, and sail angle information which it never had before.

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I was going through a major overhaul on my navigation system and decided to install an AIS receiver. There are only a few of them out there, and some of them are way overpriced for the featureset. After reviewing a bunch of online reviews, I choose the Smart Radio SR162 and the Smart Radio VHF Antenna Splitter both sold by Milltech Marine in the U.S. After a few questions to the folks at Milltech, who answered same-day with detailed technical information, and copies of the newest manuals, plus some tips, I ordered it direct.

I chose the SR162 over the SR161 since I sail and motor in a congested, busy area, and want the assurance of both A and B channels used for AIS being caught by my systems. The SR161 only listens to the A channel, which limits the amount of boats it “hears” in busy areas.

The manual online is slightly better than the printed one that comes with the unit. There are a few confusing things in it, but overall if you know NMEA 0183 and basic VHF antennas, you can set this up. First was the VHF splitter – I opted to use this since I have a single VHF antenna on the top of my mast, and I didn’t want to add a second antenna dedicated to the AIS system. The splitter installs upstream of your other VHF devices, in my case my VHF radio, and allows the AIS receiver to use an existing antenna, while still allowing you to use the antenna for other things such as VHF radios, and VHF broadcasts. The splitter was easy to install, and required power as well as re-routing my existing VHF cable. Once that was installed, the resulting cables coming from it went to my VHF radio, and to the AIS unit.

Install of the AIS unit went pretty smoothly too. It required power, the input from the splitter, and output to my chartplotter. Initially I wanted to send the AIS output to my Shipmodul NMEA multiplexer, but after extensive testing, the high speed 38,400 baud rate of the AIS receiver added too much traffic to the rest of the data going back and forth, and caused overflows. Eventually, I chose to send it directly over a high speed NMEA 0183 port directly into my Garmin 5208 chartplotter. After using a multimeter to figure out which pins were which (you need pin 2 and 5), and cabling it up, all that was left was to power it and my chartplotter up, and configure my chartplotter to show AIS information. In about 30 seconds, I started to see AIS targets and information. That was it for configuration in terms of the AIS receiver.

A few notes:

First, your chartplotter or other software needs to support AIS. Check your specs first.

Second, my chartplotter did support AIS, but it does add delay to the system overall when it’s running in a wide scan mode. One thing I don’t like about the Garmin solution is that you can’t see AIS wider than 2 nautical miles maximum. In addition, their alarms are based on MMSI or AIS targets that are within a specific distance, not necessarily based on TCPA. If you don’t know what those acronyms mean, go look on some AIS sites.

It takes quite a while for the AIS target information to update to a decent usable level – this is by design of the AIS spec, so I’m not surprised. I would recommend turning these systems on early when you think you’re going to navigate sometime soon.

In general, I’ve been very happy with the unit, and AIS in general. It’s basically set-and-forget technology, and it allows me to see things around corners and ahead of time that I would have listened for on the VHF in the past. It doesn’t replace being attentive at the helm, but it sure adds more safety to sailing. It’s already helped me prevent course changes into shipping lanes in the few weeks I’ve been using it.

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Part of my navigation systems overhaul was to replace my handheld Garmin 76C GPS with something larger and more reliable, fixed mounted, that could drive my autopilot and allow me to see electronic maps as well as plot courses.

At first, being in the computing industry for my day job, I started looking at a PC solution.  There’s lots of very well thought out software out there, and a lot of it doesn’t require expensive charts or hardware.  However, I was not comfortable trusting my entire navigation to a PC knowing what can happen to them both in general use, as well as on a boat.  One of the other concerning things was power draw.  Although a laptop can run and use a low wattage charger, I wasn’t thrilled about the prospect of inverters and such running all of the time to keep my navigation system going.

In the end, I still bought PC software which I cover in a different post, but I bought a purpose-built chartplotter as my primary device.

I reviewed solutions from Raymarine and Garmin - I casually looked at a number of others, but due to the fact that I have had both Raymarine and Garmin products in the past, and also had a Raymarine autopilot, I wanted to keep in that family of products. 

I reviewed the Raymarine E and C series chartplotters, and after building an appropriate system that included future things I wanted to expand into (radar, etc.) I was surprised at the cost.  Several parts of the system were proprietary SeaTalk protocols when they really didn’t need to be.  Regardless, the system was very well designed and met my requirements.  I went to several local stores and reviewed the units in person, and was very impressed with their options.

I also reviewed the 4000 and 5000 series chartplotters from Garmin.  The 4000 series is a non-touch screen version of the 5000 series, which is touch-screen.  Both allow you to use both NMEA 0183/0183 High Speed, NMEA 2000, and the Garmin Networking protocols.  After reviewing these units in person as well, I opted for the Garmin GPSMAP 5208.

After reviewing both manufacturers, the Garmin had a lot of features I liked.  The touchscreen interface is the single best feature in the unit over the Raymarine.  I can touch the screen no matter what condition it’s in – wet, dirty fingers, etc.  No buttons taking up unit space, and very simple design of the interface.  Moving around in the maps was a concern to me, and even some of the store clerks said in detail mode they have seen it slow down.  So far in the month of use it’s had, I have only seen the display slow down when too many AIS targets are being tracked (in excess of 40!). 

Install was a breeze, and connecting it up to my multiplexer and AIS systems, as well as the GPS antenna it came with was easy.   Within an hour I had the system mounted and running. 

I also opted for the g2 Vision card for my area, which gave me more details on port entries, aerial photos, satellite maps, and guide information for creating courses, among other things.  A lot of this information is really nice to have when visiting a strange port.

The unit is well  made, and has plenty of connectors on the back for everything you would need.  The features within the software are great – tides, currents, locations, auto navigation, clear charts, and AIS support.  I have no complaints for the featureset at all.

The system has driven my autopilot and the other parts of the system without any problems so far.  It even has settings that match my Raymarine autopilot for naming waypoints – something that plagued me in past setups.

The only issues I’ve had with it include a whine when it’s been on for a while and has lots of AIS targets, and problems with the GPS coming on initially.   The whine I’ve traced to a fan within the unit that is trying to keep it cool.  This is not annoying too much, although listening to it overnight at an anchorage might be.   The amount of AIS data it has to track in Puget Sound, specifically Elliott Bay, is pretty amazing, so the whine is fine for me. 

The second issue is one I’m still researching.  So far 5 times when I’ve turned the circuit breaker on  for the whole system, and then powered on the unit, the GPS antenna hasn’t come on.  This antenna has 5 wires – 2 for power, 2 for NMEA into the chartplotter, and one for “remote power on” which I assume is the GPSMAP unit sending a signal to the antenna to come on.  I’m not sure if it’s something related to the Garmin version of software (v2.20) that it’s running, but I can’t find any updates or similar problems.  I’ll post more if I find out.

I am extremely happy with my purchase.  I have a unit that will drive my autopilot when motoring, uses a small amount of power when sailing, supports AIS for collision avoidance, and has a wealth of other features I’ve not even figured out yet.  The touchscreen interface is amazing, and I look forward to other devices that adopt this technology.

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I decided it was time to re-wire and re-tool my entire navigation system.  I’ve written articles on parts of each of these, and they’re linked below.  Here’s a general overview of what I had, and what I wanted to do.  I started with:

• Raymarine ST2000+ autopilot with wireless remote
• Tacktick wireless instruments for depth, speed, GPS, wind, compass, heading, including NMEA interface
• Handheld Garmin 76 GPS
• Uniden VHF radio with wireless remote

None of the systems above really worked well together, other than the Tacktick instruments and the autopilot.  I used those two to sail a specific set degrees off of the wind when under sail.  The purpose this process was to increase the capabilities of the system, and make sure everything talked with everything else.

I ended up with:

• Raymarine ST2000+ autopilot with wireless remote
• Tacktick wireless instruments for depth, speed, GPS, wind, compass, heading, including NMEA interface
• Uniden VHF radio with wireless remote
• Shipmodul NMEA multiplexer with Bluetooth
• Smart Radio AIS receiver and VHF splitter
• Garmin GPSMAP 5208 chartplotter
• PC using Coastal Navigator software

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