BioSemi.nl

I have newly bought a Biosemi active two system, and set it up according to the instructions written in the manual. But I have some problems, in my study I would like to see the spectral changes during mental tasks in the brain. The problem is when I choose some electrode channels for spectral analysis, ı only see a continuous noise
I can't get the differencebetween frequency bands. Hence it has to be..
It is maybe because of my configuration, could any one has any idea about it?
Thanks in advance..

Nurhan