The Bluetooth Low Energy (BLE) advertisement messages allow estimating the location and distance between mobile devices. We analyse how the signal level varies depending on interferences, distance and the orientation of the transmitting and receiving devices. To provide a representative BLE Received Signal Strength Index (RSSI) dataset, we present a series of experimental measurements, including different receiver antenna orientations for several distances. We analyse the signal level variability as a function of distance and angle in an indoor environment. Our measurements show that the mean RSSI value equals -65.5 dBm, -78.4 dBm, -84.1 dBm and -90.8 dBm for 1m, 5m, 10m, and 16m, respectively. The standard deviation changes from 5.7 dBm through 5.9 dBm, 4.5 dBm to 3.5 dBm for 1m, 5m, 10m, and 16m, respectively. We also investigate the influence of the interference, emulating environment in which devices actively transmit BLE signals with varying intensities; on average, at every 0ms (no additional signals), 4ms and 8ms. The experiments show that from 13% to 40% fewer packets are delivered per second in the presence of interferences. Nevertheless, the RSSI characteristics remain very similar regardless of the presence of emulated traffic or not.