kohlmeise:
I build a some oscillating circuit which i would like to measure with the arduino DUE.
30MHz would be the optimal state .... 15MHz is also ok.
What is the 'it' you want to measure. If it is frequency I think you will struggle.
I am very new on this field and not very familiar to many electrical components.
So you will not know that 30MHz is a very high frequency for beginners to be playing about with. All sorts of other things affects your work at these frequencies and you will need to know a lot more than you do at the moment.