  At the faintest radio flux densities (S_1.4 < 10 mJy), conflicting results
have arisen regarding whether there is a flattening of the average spectral
index between a low radio frequency (325 or 610 MHz), and e.g. 1.4 GHz. We
present a new catalogue of 843 MHz radio sources in the ELAIS-S1 field that
contains the sources, their ATLAS counterparts, and the spectral index
distributions of the sources as a function of flux density. We do not find any
statistically significant evidence for a trend towards flatter spectral indices
with decreasing flux density. We then investigate the spectral index
distribution with redshift for those sources with reliable redshifts and
explore the infrared properties. An initial sample of faint Compact Steep
Spectrum sources in ATLAS is also presented, with a brief overview of their
properties.
