Ferrite nanoparticles with a composition of Ni0.5Zn0.3Co0.2Fe2O4 were prepared by a co-precipitation method. The sample obtained after treating at approating conditions had almost equal real permeability and permittivity, of 4.8+j0.15 (loss tangent~0.04) and 4.9+j0.10 (loss tangent~0.018), respectively, over 100MHz to 500 MHz,. This material had a refractive index n of close to 5 and a reduced impedance Z/Z0 of close to 1. These properties make the material useful to the design of miniaturized antennas at VHF-UHF (100MHz-500MHz) bands.