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We studied the radio properties of optically selected quasars with z ≥ 3. The sample constructed with quasars having theflux densities S 1.4GHz ≥ 100 mJy at z ≥ 3 and S 1.4GHz ≥ 20 mJy at z ≥ 4. The observations were conducted in 2017–2021with the radio telescope RATAN-600. Using the multifrequency quasi-simultaneous data we revealed that a peaked spectralshape is a common feature for 50% of bright high-redshift quasars, the majority of them are radio-loud with log R > 2.5. Ourdata did not reveal any significant correlation between the redshift and spectral index. The average flux density variabilityof quasars are about V ar S = 0.2 − 1.0 at 4.7–11.2 GHz.

We present the results of pilot observations of the OH megamaser (OHM) sample carried out with the radio telescopeRATAN-600 at 1.2, 2.3, 4.7, 8.2, 11.2, and 22.3 GHz in 2019–2021. When comparing the radio continuum properties ofthe OHM sample and the control sample of galaxies without detected maser emission, we determine the median spectralindex at 4.7 GHz α 4.7 = −0.59 for the OHM sample, and α 4.7 = −0.71 for the non-OHM galaxies, and steep radiospectra prevail in both samples. Subsamples of OHMs powered by active galactic nuclei (AGN) and star formation have nosignificant differences in their radio properties. AGN-powered galaxies exhibit larger scatter in a range of parameters andtheir standard deviations.