Super Low Frequency (SLF) is the frequency range between 30 hertz and 300 hertz. This frequency range includes the frequencies of ACpower grids (50 hertz and 60 hertz).
The radio services Seafarer (USA) on 76 hertz and ZEVS (Russia) on 82 hertz operate in this range, which is often incorrectly called Extremely Low Frequency (ELF). They both provide communication services for submarines at a certain depth.
PCs with sound cards are increasingly being used instead of radio receivers for this frequency range, because of their much smaller size and lower cost. Signals received by the sound card with a coil or a wire antenna are analysed by a software Fast Fourier Transformalgorithm and converted into audible sound. [1]
