While the technology may be simple, there are still issues to consider if you're buying an AIS-enabled receiver. For instance, debate continues on whether a VHF antenna should be shared between an AIS receiver and a VHF radio. Some companies are supplying signal splitters with their AIS receivers, so if you have two VHF radios aboard, the radio that shares the antenna with the AIS unit should probably be your backup set. Raymarine's AIS250 receiver module, for example, uses a signal splitter. Other companies, including SeaCAS, one of the first to market AIS to the recreational-boating market, have decided that AIS works better with its own dedicated antenna. To help reduce the clutter aloft, SeaCAS offers a dual GPS/VHF antenna for its AIS system. "Using an antenna splitter isn't recommended because it prevents you from receiving AIS position updates from a vessel while you're using your voice VHF to make passing arrangements," says SeaCAS founder Fred Pot. "The antenna splitter will reduce the sensitivity, or range, of both your voice VHF and your AIS receiver by 3.5 decibels."