 Two AIS Installation Scenarios: Receivers and Transponders
By Doug Miller, Milltech Marine Inc.
At Milltech Marine, I often get asked if I have a boat and do I use the products we sell. The answer to both questions is yes.
I have a 1988 C&C Landfall 39 center cockpit, cutter-rigged sailboat named “Significant Other”. I bought the boat second hand (actually third hand) and have been sailing her in the waters around Puget Sound, San Juan Islands, and into the Canadian waters around Vancouver Island including the Gulf Islands, Desolation Sound, Barkley Sound and a couple of offshore trips. The boat is a “go anywhere” boat and was well equipped when I bought her. However, she needed an electronics upgrade which I have been actively working on pretty much since I bought her. Since we specialize in Automatic Identification System (AIS) solutions I thought I write a few words about what I have onboard.
I originally had just an AIS receiver but have recently upgraded with an AIS transponder so I’ll divide this into some discussion on the previous setup and then some info on what I have now.
AIS Receiver Scenario
Up until a couple of months ago, I had the following marine electronics on the boat:
This diagram outlines how the devices are interconnected:
This setup works quite well and allows me to send the serial output from the SR162 AIS Receiver to both the chartplotter network and the the computer. I am also able to use the GPS and depth information from the chartplotter network in Coastal Explorer and upload waypoints from the computer to the chartplotters. The VHF Antenna Splitter really works well. I can use the best antenna at the top of my mast with both my VHF radio and the AIS receiver. I have seen speculation from some folks on various forums that the splitters do not work well. I suspect these people have never actually tried using this particular splitter. Yes, you lose a bit of signal or range but the advantages of using the best antenna on the boat outweigh the signal degradation the results from sharing the antenna. For example, I get better AIS target range with the shared antenna on the mast head than I get with a dedicated VHF antenna connected only to the AIS receiver on the stern rail. And it makes the installation much easier. The Garmin 3000 series chartplotters work well although they are clearly first generation AIS displays and do not support some basic AIS features such as having an alarm go off when an AIS target is on a collision course with you.
AIS Transponder Scenario
With the availability of Class B AIS transponders, I decided I should upgrade my setup and add the following:
- I replaced the AIS Receiver with an Comar CSB200 AIS Class B Transponder. This product and the ACR Nauticast-B AIS Class B Transponder are multi-function devices. Not only does it transmit your position and information to other vessels but it is also a dual channel AIS receiver and GPS receiver. I had originally used the ACR Nauticast-B Transponder but decided instead to use the Comar CSB200 unit.
- Since the Class B transponder can be switched into “silent mode” (i.e. turn off the transmit feature but still act as a receiver), I decided to install a switch that I can use to turn the transmit function on and off.
- I added a Vesper Marine AISWatchMate display in the cockpit which gives me an approaching vessel alarm capability and allows me to monitor AIS traffic while consuming very little DC power.
- I upgraded my VHF Antenna Splitter to a Comar AST 100 VHF Antenna Splitter so that I could now share my mast head antenna with the radio and the new AIS transponder. The older VHF Antenna Splitters will not work with AIS devices that transmit.
- I also wanted to feed the GPS data from the transponder into my DSC enabled VHF radio. This would allow me to send out an emergency broadcast with my position using my VHF radio with the touch of one button.
So, my new setup consists of the following:
This diagram shows how the new devices are interconnected (click the picture for better detail):
This new setup works well and has a bunch of advantages over the previous setup.
- With the AIS transponder I can now not only see vessel traffic around me, I can also be seen.
- I can run in silent mode if I do not wish to broadcast my position or if I want to save power.
- The AIS transponder has both a serial output and a true NMEA 0183 output. This allows me to connect the device to other onboard devices with the appropriate signal configuration.
- With the AISWatchMate if have a collision avoidance alarm system that consumes so little power I can afford to use it all the time. Since the transponder outputs both GPS and AIS NMEA data streams, I only need to connect the output NMEA pair from the transponder to the input on one port on the AISWatchMate. This makes it a very simple installation.
- I now have a backup GPS since the transponder also outputs GPS NMEA sentences. Note that with the NMEA data stream being fed from the transponder to the chartplotter I end up with two GPS feeds which is not desirable. Therefore when I have the transponder on I select the option in the Garmin network to use a NMEA GPS rather than the Garmin GPS 17.
- I decided to leave the SR162 on the boat and will keep it as a backup AIS receiver.
These are a couple of possible configuration of devices for these two scenarios – many others will work depending on the equipment you have and the functionality that you need.
More information on these products can be found on our product pages. |
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