The dataset contains 500-2000 MHz brightness temperature measurements gathered by the Ultra-Wideband Software Defined Microwave Radiometer (UWBRAD) during the Ice Sheet and Sea Ice Airborne Microwave eXperiment (ISSIUMAX) in Terra Nova Bay, Antarctica. UWBRAD was operated from a DHC-6 Twin Otter during the XXXVIII Italian Antarctic Expedition. The campaign collected the first ultrawideband brightness temperature measurements in Antarctica over different targets including sea ice, ice sheets, glaciers, ice shelves, and land. The dataset was collected on 24-25 November 2018 in the coastal region surrounding Mario Zucchelli Station (-74.694807°, 164.113268°). The UWBRAD microwave radiometer measures nadiral circularly polarized brightness temperatures over the entire 500–2000 MHz range using multiple frequency channels. Since this frequency range is not a protected portion of the spectrum, the measurements can be affected by anthropogenic RFI. To address this issue, UWBRAD includes RFI detection and filtering methods to filter out artificial signals received by the radiometer. A full description of the instrument can be found in Andrews et al, 2022 (DOI: 10.1109/TGRS.2021.3090945). The published dataset is in ascii format and consists of geolocated nadiral brightness temperature measurements collected over 12 sub-bands whose central frequencies are 560, 660, 820, 900, 1180, 1240, 1370, 1500, 1630, 1740, 1860, and 1950 MHz. Only measurements with a viewing angle within 5 deg with respect to nadir are reported.