Comparative measurements of radio frequency interference in the 10–250 MHz

Mitigation of radio frequency interferences (RFI) is crucial for improving the quality of collected radio observations. For the instruments working in the decimeter and meter ranges – LOFAR (LOw Frequency ARray) is a good example – RFI is particularly vexing thus the widest possible knowledge of man-made emissions in the vicinity of radio telescopes is highly desirable. The results of the measurements of RFI performed at the LOFAR PL612 station in Bałdy as well as the Radio Astronomical Observatory in Piwnice and the Astronomical Observatory and Astronomical Education Centre in Białków are shown and a comparative analysis has been carried out. Owing to this, solutions either to suppress RFI sources or to filter out undesirable signals in the spectra have been proposed. The results will be particularly important for the development of the LOFAR system and the extension of its usable waveband to the 10–30 MHz range. The presented measurement results also suggest the necessity to introduce a continuous RFI monitoring at LOFAR sites.