Em Trak Marine Electronics S100 AIS Antenna Splitter Reviews:
Works as advertised, and then some.
I purchased this along with the B100 AIS transceiver from the same manufacturer. It seems to work OK so far, with no noticeable loss of range. With a new AIS antenna, the VSWR reading is 1.1:1 or 1.2:1, and seems to be the same with or without the splitter installed.
The unit is very small, and shares the same form factor with the B100. One cautionary note is that despite the small size of these units, rigid connectors radiate around them in every direction. Therefore, the actual space required for installation may be much larger than you might think. Another quibble is that the main output from both of these units includes numerous tiny conductors bundled into a single cable. You will probably have to supply a terminal strip to bind these and sort out all of the possible connections. This takes even more room in the installation. Finally, assuming that the unit is mounted on a vertical panel, the indicator lights are on the bottom, where they may be impossible to see. Not that you really need to see them unless you are trouble-shooting a problem.
Two pleasant surprises. First, all of the cables that you need are included in the package, so there is no need to order or make coax patch cables. Second, though not advertised in the product description, the unit does include terminals to connect your FM stereo to the antenna as well.
Good unit, get it if you have a cabin or waterproof area for it to be installed. The FM radio antenna connection is in the power connector, having it on it's own RF connector would be better. But it works well!