Radio flux densities as a function of the observed (bottom x-axis) and rest-frame (top x-axis) frequency of PSO J191+86 from 0.150 to 4.85 GHz. The spectrum shows a peak around ∼1 GHz, and therefore the source can be classified as a GPS. The corresponding indices of the low- and high-frequency parts of the spectrum are reported together with the reference surveys. The red dashed line represents the possible spectral index according to the TGSS upper limit.