Quasi-simultaneous measurements of the ocean wave-radar modulation transfer function (MTF) were performed from the German North Sea Research Platform (FPN) at 1.0 GHz (L-band), 5.3 GHz (C-band), and 10.0 GHz (X-band) at HH and VV polarization by using one antenna. MTFs obtained at different radar frequencies and polarizations are compared. Our results show that the coherence between the radar backscatter and the long ocean wave field is a strongly decreasing function of radar frequency. A residual MTF, Mres, is calculated which is obtained by subtracting the theoretical tilt and range MTFs from the measured total MTF. The differences between Mres obtained at HH and VV polarization can partly be explained by a three-scale composite surface model.