Representative detection of a carbon α RRL towards Cas A with LOFAR. We show spectra of the RRL C538α that was measured using Data-1 (black solid) and Data-2 (blue dashed). For comparison, we have also smoothed the Data-1 spectrum to the same spectral resolution as Data-2 (red dashed). These spectra demonstrate the spectral stability of the LOFAR system for making spectral line measurements.