super low frequency

Super low frequency (SLF) radiation is defined by the ITU to be electromagnetic radiation within the frequency range of 30 to 300 Hz. It is considered within the lower-frequency end of the radio spectrum or part of subradio, i.e., beyond radio. It falls between extremely low frequency (ELF) and ultra low frequency (ULF).

Of note is that 50 Hz and 60 Hz, typical frequencies of AC power, fall within this range, thus power lines produce much of the SLF radiation around us. SLF wavelengths of are very long (1000 km and longer) which reduces the SLF produced by power lines and also generally eliminates antenna-designs that match the antenna's physical length to the wavelength.