  The microwave absorption R in the Y-Ba-Cu-O single crystals was investigated
near {T_c \approx 92 K} and in the external magnetic field {0<H \leq 9 kOe}. A
modified ESR spectrometer was used in the experiment. The method of temperature
modulation, along with the usual method of magnetic-field modulation, was first
applied in studying of the microwave response of these crystals. Peaks in the
temp erature dependencies of the signals {\partial R}/ {\partial H} and
{\partial R} /{\partial T} observed in the vicinity of {T_c} were differently
shaped and slightly shifted one with respect to another. The evolution of the
peaks with variation of the magnetic field and angle {\theta} between {\bf H}
and the {\bf c}-axis was traced. It has been shown that the observed difference
of the temperature dependencies of the derivatives {\partial R}/{\partial H}
and {\partial R}/{\partial T} occures due to the field-induced broadening of
the superconducting transition, which is inherent in the high-{T_c}
superconductors.
