Some aspects of interference on Loran-C

The expansion of Loran-C in Europe with its already heavily loaded LF frequency spectrum is a challenge to the receiver designer. The number of continuous wave (CW) interfaces often exceeds the number of notch filters available in Loran-C receivers. Thus, decisions have to be made about which interfering signals are to be suppressed. However, the complex nature of the disturbance of phase and envelope of Loran-C signals by CW interference makes understanding of the process very difficult. Therefore, a practical vector-analysis method is outlined which helps to explain the effects of asynchronous and various types of synchronous interferences and noise. The net results on the phase and envelope tracking process is demonstrated with the LOran Simulation Program LOSP which runs on a personal computer. Finally, some general ideas on interference-reduction techniques are discussed.