When it comes to safety on the boat, one of the fastest growing products is AIS (Automatic Identification System). It’s a great tool and aide when navigating on the water. One bit of confusion with boaters, is what do I use as an antenna? First things first, you need to know what type of AIS your using. Not the brand, but if it’s receive only or transmit/receive. Knowing this is half the battle with antennas.
Receive only AIS units are being integrated into many of the newer VHF radios. It will have an internal splitter between the two and only one antenna input. For this scenario a VHF antenna is needed. You’re not transmitting your position via AIS, so VHF being the most critical communication is what the antenna is primarily needed for. This is fairly straight forward.
Where this all gets tricky and the confusion lies, is when a transponder is added to the mix. This is for transmit/receive set up boats. Ultimately there should be independent antennas on the boat. One VHF antenna and one true AIS antenna. An AIS antenna will be tuned to AIS frequency of 162 MHz. VHF antennas are tuned to 156.8 MHz. Though the two frequencies are close, having an AIS antenna for your AIS system, will optimize performance. VHF antennas can work on AIS, yet the frequency of 162 MHz they will be operating at, is at the high end of the operable bandwidth of the antenna, where performance is not ideal. Many of the AIS transmit/receive units are also coming with splitters now, to utilize the same antenna as your VHF radio. The ease of not having to add another antenna to an already crowded radar arch or hardtop can seem enticing to a lot of boaters. At Shakespeare, we don’t recommend using splitters and always recommend using independent antennas, especially when it comes to VHF communication. Except for life jackets, VHF has saved more lives at sea than any other safety equipment. It is also noted that independent antennas will not always be possible. In the scenario where you are utilizing just one antenna for both VHF and AIS, the use of a VHF antenna is what the boater will need. As previously stated VHF is the most critical communication.