  We report results of Canberra-ATCA Doppler-only continuous wave (CW) radar
observations of near-Earth asteroid (163899) 2003 SD220 at a receiving
frequency of 7159 MHz (4.19 cm) on 2018 December 20, 21, and 22 during its
close approach within 0.019 au (7.4 lunar distances). Echo power spectra
provide evidence that the shape is significantly elongated, asymmetric, and has
at least one relatively large concavity. An average spectrum per track yields
an OC (opposite sense of circular polarisation) radar cross section of 0.39,
0.27, and 0.25 km$^{2}$, respectively, with an uncertainty of 35 \%. Variations
by roughly a factor of two in the limb-to-limb bandwidth over the three days
indicate rotation of an elongated object. We obtain a circular polarization
ratio of 0.21 $\pm$ 0.07 that is consistent with, but somewhat lower than, the
average among other S-class near-Earth asteroids observed by radar.
