Three different Antiferroelectric Liquid Crystals, synthesized in Military University of Technology were investigated by dielectric means. Some of them are orthoconic. The structures of studied compounds are very similar. The only one difference is presented in rigid core. The position and number of Fluorine atoms in rigid core changes. Very rich dielectric modes are detected with frequencies from 50 Hz up to 40 MHz. In this paper, dielectric spectroscopy of investigated materials is presented.