Although AIS transmitters are great if you can afford them, an AIS receiver is worth its weight in gold – or at least the $200 which seems to be about the minimum for a new model. The ships appear as triangular objects on your navigation software, pointed in direction of travel, with the ship’s name and a trajectory if available. Clicking on the ship symbol reveals the additional information such as destination and departure ports, mmsi call sign, time to closest approach (and distance at that time), current distance, etc. in a side data panel.
Your navigation software can set alerts as well – say an alert if you are due to cross paths within a mile (which sounds far but is REALLY close for a big tanker). It is a great comfort at night to know you can glance at the screen and see if there’s a large commercial boat headed your way. The alert works nicely too – you can set it to go off if a boat enters within a radius of your boat (say 10 or 20 miles), or only if the boat is expected to cross within a certain distance of your boat (say 3/4 mile). If you are alerted that a ship will cross paths with you uncomfortably close, you can use the MMSI number to call the ship and alert them to your position. Often they will not have noticed you. If you’re lucky they may be able to see you on Radar (our steel hull helps with that). Then if you say “We are due to intersect within a quarter mile. I am going to alter course slightly south, to increase that distance” then you can feel comfortable he is not also going to alter his course south without noticing you.
Before our last voyage AIS was fairly new and we used the low cost SR161 from Milltech Marine – $189. It requires an RS-232 (see below) connection to your computer, and should share your VHF antenna. It can only receive on one channel at a time, but alternates back and forth to receive Class A (large commercial) and Class B (fishing and small paying-passenger boats). This voyage I hope to use the McMurdo SmartFind M15 AIS Class B Receiver which uses USB instead of RS-232. Yeah! It also receives simultaneously on the two channels. It is $194 at the link above from Amazon or just a little higher from Landfall Navigation.
Antenna for an AIS Receiver
Of course AIS is only as good as your antenna. We share ours with our mast-head VHF antenna by means of an Antenna Splitter. The antenna splitter sits between the VHF radio and the AIS. A couple of inexpensive solutions are provided by Milltech Marine. We used the “Smart Radio VHF/AIS” model, but there is also an Comar version available at the same price, about $120.
Total Minimum Cost for AIS Receiver system
For interfacing with your PC navigation software, and assuming you already have a VHF antenna, the cost to add AIS to your navigation system is:
- AIS receiver $189
- Antenna splitter $119
- Serial-to-USB cable (unless you already have a serial-to-usb hub for other devices) $30
- TOTAL: $340