Light curves of 4C 38.41 at different frequencies in 2008–2011. From top to bottom: 1) the daily γ-ray light curve from Fermi-LAT in the 100 MeV–300 GeV range (10^-7   ph   cm^-2   s^-1); 2) the corresponding weekly γ-ray light curve with its cubic spline interpolation; 3) the X-ray light curve from Swift-XRT, derived as explained in Sect. 5.2; blue dots are counts s^-1, while black squares represent 1 keV de-absorbed fluxes (μJy), which are filled in orange when resulting from robust spectral fits; 4) the de-absorbed Swift-UVOT flux density light curve in the uvw1 band (mJy); 5) the de-absorbed GASP R-band flux-density light curve (mJy) with the cubic spline interpolation through the 7-day binned data; 6) the millimetre radio light curve at 230 GHz (Jy).