An important change to AIS installations has now come in to effect for Mono and Multi-Hull Category 0, 1 and 2 offshore racing yachts. The new 2014-2015 International Sailing Federation (ISAF) Offshore Special Regulations (click here to download), that became effective as of 1st January 2014, include an important note that all AIS antennas (VHF not GPS) must now be fitted to the top of the mast.
Due to space and antenna separation issues (see previous post on this subject), it is not possible to have both a VHF and an AIS antenna mounted at the top of the mast, so in order to meet these new regulations, a yacht will need to fit a suitable antenna splitter. It is important that this splitter is suitable for use with an AIS Transponder and we would recommend one of the latest generation of “Zero Loss” splitters that do not attenuate the VHF Radio or AIS reception.
Our SPL2000 splitter is an ideal solution and can even be used with a Class A transponder, which Category 0 Mono and Multi-Hulls are required to fit. Installation is very straight forward (all of the cables are included) and the unit should be mounted close to the VHF radio and transponder. 
Once installed, the SPL2000 will automatically feed the received radio signals to both the VHF radio and the AIS. As soon as either the radio or AIS starts to transmits, the SPL2000 instantly disconnects the other device that is not transmitting. Priority is given to VHF calls and two LED indicators on the front of the unit show when either device is transmitting.
The benefit of using a splitter, and probably the reason for this change to the regulations, is that you get maximum AIS transmit and receive range. This is obviously important when racing offshore, and with the latest “Zero Loss” technology there is now no attenuation of the received signals, which traditionally has been the biggest dis-advantage of using a splitter.
Below is a wiring diagram showing how a splitter is connected to a typical AIS Class B transponder system.
