Examples of the Faraday spectrum classes ‘small sec’ (top), ‘unresolved’ (centre), and ‘broad’ (bottom) as described in Sect. 5.2.1. The plots show the Faraday spectrum (green) and the fitted Gaussian (blue). The same is shown for the RMSF and its Gaussian fit, in lower opacity. The red vertical lines show the fitted ϕ from QU fitting and their uncertainties. The 3σ extent and the half-maximum amplitude of the fitted Gaussians are indicated with dashed grey lines.