This part of IEC 61788 describes measurement of the surface resistance of superconductors at microwave frequencies by the standard two-resonator method. The object of measurement is the temperature dependence of Rs at the resonant frequency. The applicable measurement range of surface resistances for this method is as follows: - Frequency: 8 GHz < f < 30 GHz - Measurement resolution: 0,01 milliohm at 10 GHz.