We've had one of the early Digital Yacht transponders (AIT250) on board our sailing yacht for 3-4 years now, linked in to a Standard Horizon plotter, and a PC running OpenCPN - both work seamlessly. And service from Standard Horizon is superb.
Position the aerial as high as you can, and use the best aerial possible - AIS B transmit is only 2W (as opposed to your VHF radio's 25W max). We have a Helix stub antenna mounted on the radar arch that's fairly useless - when I delivered a friend's yacht to to Scotland last year, he had a full size aerial mounted in the same place, and the effective range of his AIS transmit and receive was far greater than ours!
__________________
|