The relationship between the dielectric and radio brightness characteristics of aqueous solutions of (NH4)2[PdCl4] at low concentrations at 298.15 K were considered. The dielectric relaxation parameters representing the disturbance of the H-bond network in the transition from water to solution were calculated from experimental data on the complex permittivity near the maximum of dispersion of water and solutions. These data and the Fresnel equations were used to find the quasi-optical coefficients and radio brightness characteristics of aqueous solutions in the centimeter and millimeter bands. The radio brightness characteristics of model solutions were determined with a high-sensitivity radiometer at a frequency of 61.2 GHz. The radio brightness temperature in the model solutions decreases in the transition from water to solution according to both experimental and calculated data. It was shown that the intrinsic radiation of the solution reflects the contributions of both dipole and ionic losses, which still remain significant in the millimeter band. They may even determine the difference in the signs of the changes in the radio brightness. Basics of a new approach to studying solutions containing complex ions based on their intrinsic radiation in the millimeter band were developed.