The paper contains an analysis of the classical Preisach model from a frequency point of view. A Fourier analysis retrieves the necessary and sufficient conditions on the Preisach weighting function to have an output with half-wave symmetry, i.e. only odd harmonics to be present. For a wide class of weighting functions, it is shown that all odd frequencies are present. As a consequence, a filtering method is suggested that enhances time-series data from sinusoidal input, which can be used for Preisach model identification.