Strong fluctuations of lower hybrid waves (LHW) amplitudes inside the plasma have been observed in experiments with different types of launchers. The fluctuation frequency is much higher than the frequency of plasma density fluctuations. This effect is explained by the presence of plasma fluctuations along the whole ray path. LHW spectrum broadening has been found by means of a double radiofrequency probe. This experimental result supports the assumption of spectral gap filling between the electron velocity distribution function and the spectrum launched into the plasma.