Production of self-absorbed synchrotron spectra steeper than nu to the 5/2

Self-absorbed synchrotron radiation produced by electrons with a power-law distribution of energies has a unique spectral shape: intensity is proportional to nu to the 5/2, where nu is the frequency, irrespective of the power law index of the electrons. It has been asserted that the measurement of a spectral index greater than 5/2 at frequencies below the 'far-IR turnovers' observed in the spectra of many radio-quiet AGN is incompatible with the physics of self-absorbed synchrotron sources. It is shown here that plausible electron energy distributions can lead to self-absorbed synchrotron spectra which are steeper than nu to the 5/2 over 1-1.5 orders of magnitude in frequency. This indicates that none of the existing observations are in fact incompatible with self-absorbed synchrotron radiation as the source.