 The fast Fourier transform is a wonderful tool, but it can be a daunting one. All it does is return a long list of complex numbers. To find the frequency of each item in the list, you have to take that item's position, k, divided by the number of items in the list, n, and multiplied by the sampling frequency, fs. But the FFT will only test n different frequencies, with the jump between frequencies being equal to the sampling frequency divided by n. How can you reduce the size of this jump and increase the frequency resolution of your FFT? You have to increase the size of the list. But remember, for your FFT to work, the number of samples or points in your FFT must be a power of 2. Therefore, if you sample your signal for twice as long, you'll halve the size of the jump between frequencies and double the frequency resolution of your FFT.