Thanks for all the suggestions.

For the record, the AIS, depth transducer and radar are the only devices connected to the HDS, I have set the baud rate to 38,400 and it has an integrated GPS.

As an aside, I had no problems installing the broadband radar antenna. It worked first time and so far I am pleased with it. The close in resolution is impressive. I haven't had a chance to take it out and experience it's ability to distinguish between clutter and small targets at a distance, multiple close together targets, etc. and only time will determine its long term reliability.

Tomorrow, I will have the ProAIS software on the laptop and a be able to connect it to the AIS rs-232 port to verify that it is at least putting out the data. I think I'll also take my oscilloscope down with me so I can verify that *something* is being sent out the rs-422 wires (which connect to the HDS). I can also use it to verify my wiring job by checking that the data is present at the HDS input wires. I'll be prepared to use jumpers to bypass my wiring job. Once that's verified, I can assume that the problem is with either the HDS, or the settings in the HDS. The Lowrance support line will be open (they're only manned M-F) and they will hopefully be able to give me some help with the HDS settings.

My general experience with support lines over the years has not been good. Usually, the only people that you can get through to know nothing about the product and all they can do is read the manual to you. A notable and surprising exception was Raymarine. The one time I tried to use their support, I was in Panama and had just bought an ST-3000 wheel pilot that wouldn't work. When I called, I was actually able to get an engineer on the line and was given instructions that allowed me to open up the control unit and reverse two connections to correct the problem.