Computation of the horizontal size of the RATAN-600 beam pattern for the “Southern Sector with a Flat Reflector” mode with allowance for the parameters of primary feeds

We report the spectra of the horizontal size of the beam pattern of the RATAN-600 radio telescope operating in the “Southern Sector with a Flat Reflector” observing mode computed in the geometrical optics approximation with allowance for the beam patterns of various primary feeds used in observations with the solar receiver facility in the 3–18 GHz frequency interval. In particular, we show that in the case broadband, spiral, or sinuous feeds are used, the width of the horizontal beam pattern of the antenna decreases with wavelength in the low-frequency part of the spectrum.We compute the spectra of the sizes of two compact local sources on the Sun, which show that the results obtained have to be taken into account when determining the parameters of local sources.