Three new antiferroelectric mixtures W-1000, W-1000A and W-1000B and their components W-1, W-2 and B-3 synthesized at Military University of Technology were investigated by dielectric spectroscopy. Typical relaxation modes in smectic phases and one mode in isotropic phase never observed before were detected. Obtained results were discussed in terms of composition of investigated mixtures and molecular structures of their components.