pick up a copy of "radar for mariners" by david burch (glen from tht suggested) it is very useful and worth reading before you spend the money if you are that unfamiliar with radar. one caution; there is some EXTREMELY technical sections that might make your head hurt. the majority is very straightforward and will definitely help in making your decision. some of the info is a little dated (recent advances not fully covered), but it is great reference. ron