The impact of station far sidelobes on EoR/CD power spectra
  Stations of dipole antennas for SKA1-Low will comprise 256 elements spread
over an area with a diameter of 38~m. We consider the effect of residual
unsubtracted sources well outside of the main beam for differing numbers of
unique station configurations, in the Epoch of Reionisation (EoR) and the
Cosmic Dawn (CD), both in simulation and with theoretical considerations. We
find that beam sidelobes imprint power that renders the cosmological signal
unobservable over a range of scales unless compact sources are subtracted
beyond \theta_Z=30 degrees from zenith, and that station apodization will
likely be required to control far sidelobes. An array with N_b=4 unique station
configurations is sufficient to reduce the contamination, with an increase to
N_b=8 showing little improvement. Comparison with an achromatic Airy disk beam
model shows that beam sidelobe level is the main contributor to excess power in
the EoR window, and beam chromaticity is less relevant. In the EoR, z=8.5,
subtracting sources above 200~mJy out to \theta_Z=45 degrees, will be required
to access relevant modes of the power spectrum.
