The article describes experimental and theoretical researches of interaction of the microwaves (from 2.0 to 4.2 GHz) with silicon carbide powders characterized by fractal structure and water solutions NaCl and LiCl. The changes of the form of registered signals and the spectrum displacements in the Stocks area of frequencies were experimentally observed. The peak-frequency characteristics of signal spectra were analyzed. The high precision in the definition of frequency (10^-9-10^-10) allowed to reach the sensitivity of spectrum displacement in the Stocks area of frequencies (5-6)*10⁹ Hz/m = 5-6 Hz/nm.