This article solves the problem of determining the influence of an extended plasma jet on the radiation pattern of a short-grounded antenna in the frequency range of 1-3 GHz. The electron density and the electron collision frequency are set such that they correspond to atmospheric plasma jets of a barrier discharge in a helium flow. The problem of determining the radiation pattern is solved numerically using ANSYS HFSS and analytically using simple theoretical expressions for the field of a short antenna. The results using these two approaches are consistent with each other well. Based on the obtained results, a novel microwave diagnostic method for the atmospheric plasma jets was proposed.