[en] Superconducting YbCO-layers on various substrates (MgO, Si und GaAs) were investigated at 35 GHz and in the temperature range from T_c to 4.2 K. For films on semiconductor substrates it was found that for thickness≤100 nm the leakage transmission into the semiconductor is so large that their application in an integrated super-semi-conductor arrangement makes little sense. Successful measurements were made of an effective surface resistance which combines transmission losses and resistive dissipation by using a TE₀₁₁-resonator is a conventional arrangement (film thickness 200, 300 and 400 nm on MgO). The comparison makes clear that Rs includes transmission losses. The intrinsic resistance R_s(T) and the penetration depth λ_L(T) cannot be determined simultaneously in such an experiment. We have developped a microwave Fabry-Perot type of measurement for this purpose. In this arrangement the wavefield are transformed into a circularly polarized mode and coupled via impedance transforming resonators to the main cavity. With this three resonant cavities arrangement we have succeeded in obtaining the resonant Fabry-Perot transmission signal and with it we determine both R_s(T) and λ_L(T). The variation of these quantities for the best of the TBCO on MgO substrates closely follows the behaviours for single crystals. It provides the first such evidence for thin films. We report the measurement of surface impedance changes caused by a magnetic field using the triple resonator Fabry-Perot system. (orig.)