Integrated radio spectrum of the inner lobes of NGC 6086. Red circles show the flux density measurements presented in this paper, blue circles show the flux densities listed in Murgia et al. (2011) connected without fitting, and the black point is the flux density measured by the TGSS all-sky survey of the GMRT at 147 MHz and 25 arcsec of resolution (Intema et al. 2017). The green line represents the best linear fit using the values in the range 144–1400 MHz (with dashed extensions to emphasise the spectrum curvature and difference with respect to the literature flux density values). The best-fit spectral index is shown in the legend.