The F₂ layer over Antarctica is influenced by factors which vary with Universal Time. The ionization density inside the auroral zone in winter mainly depends on these factors but their influence is also detectable outside this region. The time when the layer is lowest is also approximately constant in UT. Similar behavior can be detected over an even wider area in summer. The changeover from winter- to summer-type diurnal variations occurs very suddenly at certain stations but the date of change varies with station position. Studies of f₀F₁ at constant solar zenith angle show that changes comparable with the solar cycle variation occur with dip angle, magnetic activity and the separation of the F₁ and F₂ layers. Some studies of polar cap absorption (PCA) events using Antarctic f_min data are described and a list of PCAs detected in Antarctica is given.