Tag Archives: VHF

Terrapin Electronic Upgrade, Part II

I see you, do you see me?

In phase 2 of my electronic system upgrade on Terrapin, I installed a Vesper XB8000 AIS transceiver. Automatic Identification System (AIS) is a means of broadcasting the location and information about a ship using VHF radio frequencies.  It is used world-wide by commercial ships as well as recreational boats, and increasingly, other objects like buoys and personal locator beacons.  However, there are a lot of boats that do not have an AIS transmitter, so you can’t rely on AIS to see all ships in your vicinity.  It is nonetheless useful to see commercial ships and large yachts who typically broadcast AIS. If you want to see other vessels transmitting AIS, you only need a receiver, but if you want others to see you, you need a transceiver.  AIS transmits vessel data such as name, size, type of vessel, speed, heading and the Maritime Mobile Service Identity number (think cell phone number for your boat).  The really cool thing is that a vessel transmitting AIS data shows up as a little triangle on your chartplotter, so you can see exactly where it is relative to your own boat.  If you put the cursor over the boat icon, you will see all the information about the boat.   I was sold on AIS when we chartered a catamaran in the Caribbean that had AIS and I could “see” our friend’s boat from 5 miles away on the chartplotter as we rendezvoused.  The AIS unit is basically a small device that can be mounted out of sight and connected to the N2K backbone with a drop cable.  It also needs to be connected to a VHF antenna, preferably at the top of the mast, and an external GPS antenna.  An AIS transceiver can also share the same VHF antenna as the VHF radio using a splitter.  I chose the Vesper Marine AIS transceiver because it had a great reputation and it also had WiFi, so that the AIS data and N2K data could be transmitted to the WiFi system on Terrapin (See blog post How to Get WiFi on a boat).  The Vesper AIS also has a great anchor watch app that will track the location of the boat during anchoring and alert you if the boat drags anchor.

Because of the importance of GPS for an AIS system, they are designed to have a dedicated input from a GPS “mushroom” antenna located in an outside area with a clear view of the sky.  The vesper came with its own GPS antenna which I mounted on the stern rail and routed the coaxial cable to the inside locker where the AIS device is located. An added benefit is that this GPS antenna became the main GPS source for the Zeus chartplotter as well.  Again, this illustrates the benefit of the N2K system.  Because the AIS unit is attached to N2K, the chartplotter has access to not only the AIS data, but GPS data as well.  The Zeus 2 chartplotter also has it’s own GPS antenna, but it is built into the chartplotter itself which is under the solid fiberglass bimini.  It works, but it is not as sensitive as the dedicated AIS GPS. 

The Vesper VHF splitter is a small device that allows the use of the same mast top VHF antenna for both the VHF radio and the AIS transceiver. It is a powered unit that has several great features and is well worth the expense.  It actually amplifies the AIS signal and improves the sensitivity of the AIS.  It also gives the VHF radio priority and maintains an antenna connection for the VHF radio even when power to the splitter is off.  The splitter also has indicator LEDs that indicate whether the AIS or the VHF is transmitting and a red LED to warn if there is a problem with the antenna circuit.  Hookup was easy.  I removed the VHF antenna cable from the VHF radio and attached it to the Antenna Out on the splitter.  The VHF radio was then attached to the splitter “VHF IN” connector and the AIS unit was attached to the splitter via the “AIS IN” connector.  The splitter than needs to be connected to a 12Vdc source, switched on the same breaker as the AIS unit itself.  This is important because the AIS can be damaged if it tries to transmit without an antenna connected.

Initial configuration of the Vesper XB8000 was a little bit convoluted but not too bad if you follow the directions in the on-line manual.  Basically it involves downloading a configuration utility onto a laptop or ipad and connecting to the Vesper AIS directly with a USB cable.  Once I did this, I was able to update the firmware, and configure the WiFi to connect to the Terrapin WiFi router.  I then installed the Watchmate app on my smartphone and was also able to see AIS data and use a very good anchor watch program.

Last but not least, the AIS unit was easily attached to the N2K network with a short drop cable and tee. When I powered up the Zeus chartplotter I was able to see AIS targets all around my area, very cool!  In the settings menu, the Zeus chartplotter also recognized the GPS antenna connected to the AIS unit and asked which GPS I wanted to use: the Vesper or the Zeus.  For reasons described above, I chose the Vesper GPS. 

The Vesper Marine AIS installed on Terrapin has been working flawlessly now for three seasons. Most boats in my sailing area, south-west Florida, do not have AIS so it is not particularly useful for collision avoidance or tracking other boats.  However, as I cruise in areas with more commercial traffic, I will be glad to be able to see these ships.  I believe there are a lot more recreational vessels that have AIS receivers because many VHF radios now have built-in AIS receivers.  In this case, many more vessels will be able to see me.  In one situation, we were following friends on another boat to one of their favorite anchorages off Boca Grande.  Since they were a power boat, they got ahead of us and we lost sight of each other.  However, they could easily see us on AIS and gave us a few course alterations as we approached.