  Quantum oscillations amplitude of multiband metals, such as high T c
superconductors in the normal state, heavy fermions or organic conductors are
generally determined through Fourier analysis of the data even though the
oscillatory part of the signal is field-dependent. It is demonstrated that the
amplitude of a given Fourier component can strongly depend on both the nature
of the windowing (either flat, Hahn or Blackman window) and, since oscillations
are obtained within finite field range, the window width. Consequences on the
determination of the Fourier amplitude, hence on the effective mass are
examined in order to determine the conditions for reliable data analysis.
