Modified 8bit FFT in c

Hi,

hope that anyone can help: will use this FFT for some HAM projects. Question: how can I reduce the bandwidth from 330hz to 3300 khz only?

Most HAM radios have audio bandwidths from 0 to 3khz.

And: how can I use 128 or 256 FFT level instead of 64?

Thank you very much fpr information.