Nigel,
You won't be able to get RAI FTA in North America. Rai International started to encrypt their signal about 2 years ago, I think. There is a NTSC feed called Rai Italia on AMC-1. But, it is a promo channel more than anything for Rai International and they only transmit 16 hours a week. For some people that's enough. You will need a C-Band dish to receive this channel and an anolog C-Band receiver.
Now, if you live in Europe RAI's major networks are FTA on Hotbird 3. These are on Ku-Band. Hence, you can see the different between Europe and North America.