Top panel: schematics of the particle distribution responsible for the spectra of the bottom two panels. The dashed blue line corresponds to the injected [Q(γ)] distribution. The characteristic Lorentz factors and frequencies are labelled as described in the text. The solid and dashed lines are re–scaled by an arbitrary amount. Bottom two panels: sketch of synchrotron spectra as reproduced by the spectral analysis discussed in the text. The spectra show a high-energy exponential cut-off which is not always present or detectable in real data.