i am also currently working on the same project ie to design a wireless transciver which could be able to snd data upto km range
i am using atmaga48 with rfm12bp
let me nu wat type of help u need
I also have developed code for RFM12 (not B or BP, but should only be a small difference). What I made can be seen when you follow the link in my signature. My project is semi-duplex (hard to get that working) and I have basic modules available that will do the trick for you.