Best Practice AIS Installation for Satellite Reception

Recreational vessels fitted with Class B AIS transponders can be tracked by satellite receiving stations provided the installation is completed to a high standard.

The two popular configurations are;

  1. AIS transponder and VHF radio sharing a common masthead antenna
  2. AIS transponder connected to a dedicated antenna mounted on a post or radar arch at the stern.

For both configurations I recommend the Vesper VA159 Shared AIS + VHF Antenna.

In the case of a masthead configuration, it is IMPERATIVE the antenna chosen is designed for both VHF Radio and AIS transponder use.  

You can use an AIS only designed antenna for the dedicated antenna configuration, but consider a shared AIS + VHF antenna, as this becomes a great backup for your VHF radio should your vessel be dismasted.

If you use an incorrect antenna type, the signal transmitted by the AIS will be impaired to the extent that it is not received reliably by satellite receivers.

In both configurations, low loss coaxial cable is required to minimize signal loss.  I recommend Ancor RG-213 marine grade coaxial cable.

This is particularly important on the long run from the masthead to the splitter device located below deck.  

Do not be tempted to save money and use RG-8X or RG-58CU cable.  Satellite reliability will be severely impacted.

In a shared masthead configuration, you need a splitter to connect both the AIS transponder and the VHF radio to the same antenna.

If your AIS transponder does not have an internal splitter, I recommend the Vesper SP160 AIS / VHF Splitter.

If any of your AIS equipment is supplied with flimsy short coaxial patch leads, do not use them.  Instead have a technician make up leads of the required length using RG-213 cable.

Make sure that all cables / connections are sealed from the weather using self amalgamating tape.  If you are upgrading an existing installation, I recommend you replace it all.  Don't trust what you cannot see.

Finally, upgrade to a Class B+ (SOTDMA) AIS transponder.  The higher output power of 5 watts (compared to 2 watts for Class B) increases reliability for satellite reception.

Following the above best practice will give your vessel the best possible chance of being seen from the sky no matter where you are.  It will also enhance the range of your AIS for collision avoidance at sea.