Top panel: spectral index profile between 1030 and 1398 MHz computed along the filament at the locations shown by the slices in the inset (see text for details). Middle panel: peak brightness at 1030 MHz (blue triangles) and at 1398 MHz (red triangles) along the filament at the location of the slices. Bottom panel: deconvolved FWHM at 1030 MHz (blue dots) and at 1398 MHz (red dots) along the filament at the location of the slices. The plotted error bars are comparable to the size of the dots.