A method for calibrating a radio frequency test instrument is described wherein a first frequency response is measured using a radio frequency and coarse intermediate frequency grid. A first matrix is created comprising data obtained from said first frequency response measuring. A second frequency response is measured using a radio frequency and fine intermediate frequency grid. A second matrix is created comprising data obtained from said second frequency response measuring. Said first matrix and said second matrix are processed and combined in order to determine a frequency response for a radio frequency desired, said first matrix and said second matrix comprising data obtained from measurements performed with different radio frequency and intermediate frequency grids. Further, a radio frequency test instrument is described.