AIS antenna splitterNov 12, 2012
Occasionally I run across a product that so impresses me that I take the time to thoroughly research it and then pass on my conclusions to you. The Si-Tex Metadata AIS Antenna Splitter is one of these exceptional products and in fact it is included in one of 23 featured products that were recently nominated for the NMEA Technology Award for 2012. It could be a good product for you and your boat and here’s why.
Although some countries have mandated that all or most vessels carry an Automatic Identification System (AIS) transponder, here in the U.S. carriage requirements for recreational boaters are on a voluntary basis, at least for now. This could change in the future especially with full implementation of the U.S. Coast Guard’s Nationwide Automatic Identification System which already currently receives 64 million AIS messages per day from approximately 7,900 unique vessels. Of course it is just common sense and good prudence for all recreational boaters to want to carry their own Class B AIS on board for safety’s sake.
The Class B, which was introduced in 2007, is a low-cost AIS transceiver designed for non-SOLAS ships. These transmit at only two watts, typically once every 30 seconds giving them an effective horizontal range of five to 10 miles which makes them perfect for smaller craft who want to know the location of other traffic and, even more important, want the other traffic (especially big ships) to know their location. The Class B are comprised of a VHF transmitter and two VHF receivers, one of which is hard-wired to the DSC receiver and an active GPS antenna. Because these AIS use VHF transceivers to transmit and receive data it is most convenient to use the already installed VHF voice communications antenna. This is where the Si-Tex Metadata Antenna Splitter comes in handy.
The Si-Tex unit is actually a smart device that acts like a traffic cop to always give priority to the VHF digital selective call radio for transmitting. When not transmitting, both radios receive signals simultaneously and the AIS transmits data every 30 seconds. If there is ever a conflict between which transmitter gets the antenna it is always the voice DSC that wins out. If for some reason the unit has a failure, the voice communications radio is locked on to the antenna so there is no danger of losing ship to shore communications. In addition, this smart unit also provides enough receive amplification to negate any possible loss of signal due to insertion or antenna line attenuation. Two other really nice features are the colored LED indicator lights and the connection for an FM broadcast radio if the boater so desires. The LEDs let you know that there is power to the unit and that both the VHF DSC radio and AIS are transmitting.
With the use of an antenna splitter, the boater saves a lot of hassles that come with sitting another VHF antenna in an already crowded topside environment, not to mention the cost of the additional antenna, coaxial cable and connectors. With one less VHF antenna topside you could be alleviating any potential interference from another transmitting antenna desensitizing or overloading a nearby receiver. If you would like to check out the Metadata AIS Antenna Splitter go to: