Super low frequency
Encyclopedia
Super-low frequency is the frequency
range between 30 hertz
and 300 hertz. This frequency range includes the frequencies of AC
power grids (50 hertz and 60 hertz).
The radio services Seafarer (US) 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.
PC
s with sound card
s 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 transform
algorithm
and converted into audible sound.
Frequency
Frequency is the number of occurrences of a repeating event per unit time. It is also referred to as temporal frequency.The period is the duration of one cycle in a repeating event, so the period is the reciprocal of the frequency...
range between 30 hertz
Hertz
The hertz is the SI unit of frequency defined as the number of cycles per second of a periodic phenomenon. One of its most common uses is the description of the sine wave, particularly those used in radio and audio applications....
and 300 hertz. This frequency range includes the frequencies of AC
Alternating current
In alternating current the movement of electric charge periodically reverses direction. In direct current , the flow of electric charge is only in one direction....
power grids (50 hertz and 60 hertz).
The radio services Seafarer (US) on 76 hertz and ZEVS
ZEVS
Zevs or ZEVS may refer to:* ZEVS, A Soviet/Russian submarine communication system, see Communication with submarines.* Zevs, A French street artist, see Zevs...
(Russia) on 82 hertz operate in this range, which is often incorrectly called extremely low frequency
Extremely low frequency
Extremely low frequency is a term used to describe radiation frequencies from 3 to 300 Hz. In atmosphere science, an alternative definition is usually given, from 3 Hz to 3 kHz...
(ELF). They both provide communication services for submarines at a certain depth.
PC
Personal computer
A personal computer is any general-purpose computer whose size, capabilities, and original sales price make it useful for individuals, and which is intended to be operated directly by an end-user with no intervening computer operator...
s with sound card
Sound card
A sound card is an internal computer expansion card that facilitates the input and output of audio signals to and from a computer under control of computer programs. The term sound card is also applied to external audio interfaces that use software to generate sound, as opposed to using hardware...
s are increasingly being used instead of radio receivers
Receiver (radio)
A radio receiver converts signals from a radio antenna to a usable form. It uses electronic filters to separate a wanted radio frequency signal from all other signals, the electronic amplifier increases the level suitable for further processing, and finally recovers the desired information through...
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
Antenna (radio)
An antenna is an electrical device which converts electric currents into radio waves, and vice versa. It is usually used with a radio transmitter or radio receiver...
are analysed by a software fast Fourier transform
Fast Fourier transform
A fast Fourier transform is an efficient algorithm to compute the discrete Fourier transform and its inverse. "The FFT has been called the most important numerical algorithm of our lifetime ." There are many distinct FFT algorithms involving a wide range of mathematics, from simple...
algorithm
Algorithm
In mathematics and computer science, an algorithm is an effective method expressed as a finite list of well-defined instructions for calculating a function. Algorithms are used for calculation, data processing, and automated reasoning...
and converted into audible sound.
External articles
- Tomislav Stimac, "Definition of frequency bands (VLF, ELF... etc.)". IK1QFK Home Page (vlf.it).
- NASA live streaming ELF -> VLF Receiver