MeerKAT Primary Beam Measurements in the L Band
  Full-polarization primary beam patterns of MeerKAT antennas have been
measured in L-band (856 to 1711 MHz) by means of radio holography using
celestial targets. This paper presents the observed frequency dependent
properties of these beams, and guides users of this 64 antenna radio telescope
that are concerned by its direction dependent polarization effects. In this
work the effects on the primary beams due to modeling simplifications,
bandwidth averaging, gravitational loading and ambient temperature are
quantified within the half power region of the beam. A perspective is provided
on the level of significance of typical use case effects. It is shown that
antenna pointing is a leading cause of inaccuracy for telescope users in the
presumed beam shape, introducing errors exceeding 1% in power near the half
power point of beams, owing to a telescope pointing accuracy of $\sigma\approx
0.6$ arcminutes. Disregarding these pointing errors, variability in the Stokes
I beam shape relative to the array average is most commonly around 0.3% in
power; however, the impact above 1500 MHz is on average triple that of the
lower half of the band. This happens because the proportion of higher order
waveguide modes that are activated and propagate is sensitive to small
manufacturing differences in the orthomode transducer for each receiver.
Primary beam correction verification test results for an off-axis spectral
index measurement experiment are included.
