Detection of phase transitions in high-Tc superconductors by means of microwave radio pulses

YBaCuO ceramics bridge is used for investigation of Josephson transitions (JT). At 77 K, JT critical current was 1.3 mA. JT VAC consisted of 2 sections: the first one had 30 mOhm differential resistance at currents ranging from the critical one to 6.5 mA, and the second section - 64 mOhm resistance. Microwave power of about 15-20 MW with 7.8 GHz carrier frequency modulated by 1 kHz meander was applied to the bridge through microband transformer of PTL impedance (50/3 Ohm). The experimental results show that V(T) dependence has two maximums at 81 and 91 K which can correspond to the temperatures of superconductivity phase transitions. In addition, voltage pointing to the existence of a SC state, was recorded up to 130 K which could be explained by the presence of SC phase fragments and quantum fluctuations