  We report a procedure to determine the frequency-dependent conductance of
quantum Hall structures in a broad frequency domain. The procedure is based on
the combination of two known probeless methods -- acoustic spectroscopy and
microwave spectroscopy. By using the acoustic spectroscopy, we study the
low-frequency attenuation and phase shift of a surface acoustic wave in a
piezoelectric crystal in the vicinity of the electron (hole) layer. The
electronic contribution is resolved using its dependence on a transverse
magnetic field. At high frequencies, we study the attenuation of an
electromagnetic wave in a coplanar waveguide. To quantitatively calibrate these
data, we use the fact that in the quantum-Hall-effect regime the conductance at
the maxima of its magnetic field dependence is determined by extended states.
Therefore, it should be frequency independent in a broad frequency domain. The
procedure is verified by studies of a well-characterized $p$-SiGe/Ge/SiGe
heterostructure.
