(a) FFT pattern of a ducted whistler, measured on board of Compass-2 satellite on 28.02.2007 07:32 UT by the SAS2-K2 instrument. Logarithmic power spectrum of electric and magnetic field components are displayed in relative scale, (b) the FFT patterns of the computed (UWB modeled) theoretical whistler components, propagating between two layers of inhomogeneities, the E _y (upper panel) and E _z (lower panel) components, and (c) the H _y (upper panel) and H _z (lower panel) components. The y direction is orthogonal to the direction of propagation and to the layers of inhomogeneities; the z direction is orthogonal to the direction of propagation and parallel with the layers of inhomogeneities. Above the FFT pattern of the modeled UWB signals the computed time functions of the modeled field strengths are presented (Ferencz et al. 2009).