Ni-Co-Zn nanosized particles of composition Ni0.5Zn0.3Co0.2Fe2O4 were successfully prepared by co-precipitation method. After sintering the average grains size is about 100nm. The material obtained after adequate heat treatment lies between ceramic (with porosity equal to 15%) and composite medium. It shows almost constant complex permeability and permittivity in the frequency range from 100MHz to 1 GHz, and equal to ~3.5-j0.15 (loss tangent~0.04) and ~6-j0.13 (loss tangent~0.02) respectively. The refractive index n is close to 4.85. Relaxation phenomenon takes place at 2.34 GHz, an unusual high value for spinel ferrites. These electromagnetic properties, in particular the low levels of losses, show that this material could be useful to the design of miniaturized antennas in the VHF-UHF (30MHz-500MHz) range of frequency.