The template SED of 3C 48, redshifted to z = 5, boosted in flux by a wavelength-independent factor of 5 and dimmed in the optical and NIR following a Calzetti et al. (2000) extinction law with A_V = 1. To emphasise that this SED is the one of an IFRS, we give the detection limits of the SWIRE survey described in Sect. 1 as well as the 160 μm limit of the planned Herschel Hermes survey. The radio spectral index of this SED corresponds to α =  −1.4.