We report the results of high-sensitivity 4.8 GHz observations of four
southern contact-binary stars (AE Phe, YY Eri, RW Dor, and V757 Cen)
made with the Australia Telescope Compact Array. None of these stars w
ere detected above a 4sigma level of 0.4 mJy. A comparison of the radi
o emission properties of contact binaries (derived from this study and
from the literature) to those of short-period RS CVn stars, suggests
that a decrease in the dynamo efficiency of binary stars as they appro
ach contact may be required to explain the lower intrinsic radio lumin
osity of contact binaries.