  The origin of the inner dust cavities observed in transition discs remains
unknown. The segregation of dust and size of the cavity is expected to vary
depending on which clearing mechanism dominates grain evolution. We present the
results from the Discs Down Under program, an 8.8 mm continuum Australia
Telescope Compact Array (ATCA) survey targeting 15 transition discs with large
(> 20 au) cavities, and compare the resulting dust emission to Atacama Large
millimetre/sub-millimetre Array (ALMA) observations. Our ATCA observations
resolve the inner cavity for 8 of the 14 detected discs. We fit the
visibilities and reconstruct 1D radial brightness models for 10 sources with a
S/N > 5sigma. We find that, for sources with a resolved cavity in both
wavebands, the 8.8 mm and sub-mm brightness distributions peak at the same
radius from the star. We suggest that a similar cavity size for 8.8 mm and
sub-mm dust grains is due to a dust trap induced by the presence of a
companion.
