ABSTRACTIn Western Europe, the radionavigation system Loran‐C experiences serious interference problems from harmonic (HM) signals passed by the input bandpass filter. Since the influence of an HM signal on the performance of a Loran‐C system depends strongly on the signal's frequency, the frequency spectrum must be analyzed with high resolution for an optimal interference suppression strategy. Only the signals with a harmful influence on the operation of the Loran‐C system must be suppressed. The approach taken in this paper is to apply a special windowing function in the time domain, together with a nonstandard sampling pattern in the frequency domain, when performing spectrum analysis. The spectral weighting created in this way corresponds with the receiver's sensitivity for interference signals. Therefore, the signal detected as the most powerful will be equal to the most ha