The nRF52 DK has s a λ/4 monopole antenna, so from theory you should expect a single doughnut shaped lobe, with field strength declining monotonically from a maximum in the horizontal direction, similar to the illustration used in this article. I suspect that the actual radiation pattern of the DK antenna deviates significantly from the ideal case, but unfortunately we do not have actual measurements of the radiation pattern of the DK specifically.
