A study of the spectral properties of positive spots on multifrequency Planck maps near RCR sources showed their identity with the spectral properties of NVSS sources and closest objects of the Planck catalogue associated with them. In both cases, a linear correlation was found between spectral indices of radio sources in the range of 0.15 - 3.94 GHz and spectral indices of closest spots (of Planck objects) in the frequency range 30 - 217 GHz. The compare of the combined spectra of RCR sources and closest positive spots with the combined spectra of NVSS sources and associated with them objects from the Planck catalogue suggests that the spots found near RCR sources may be manifestations of them in the sub-millimeter range, and most of the spots are extragalactic in nature. Part of the combined spectra of RCR objects and nearby positive spots can be explained by the variability of radio sources. The spectrum of averaged temperatures of hot spots detected near RCR sources was constructed, which showed a quantitative excess over those obtained earlier by modeling, which can be explained by the influence of synchrotron background or the contribution of radio source to radiation in the submillimeter range. The contribution of these unaccounted for radio sources to the foreground background can affect the resulting map ofthe cosmological microwave background.