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In this paper, a low-loss Ni-Mn-Co ferrite (Ni0.76Mn0.24-xCoxFe2O4 with x = 0-0.04) has been developed for miniaturization and performance improvement of mobile handset antennas. The developed ferrite material has almost equal permittivity and permeability of 7-9, as well as sufficiently low dielectric and magnetic loss tangent less than 0.001 and 0.01 below 200 MHz, respectively. Miniaturization factor of about 8 and normalized impedance of about 1 were obtained at 200 MHz. A helical antenna operating at terrestrial digital multimedia broadcasting (T-DMB, 174-216 MHz) band was fabricated on the ferrite substrate, which has compact size, low loss, wide bandwidth, and good radiation performance.