Low frequency
Encyclopedia : L : LO : LOW : Low frequency
| low frequency (LF) |
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| Cycles per second: 30kHz to 300kHz Wavelength: 10km to 1km |
Low Frequency or LF refers to Radio Frequencies (RF) in the range of 30–300 kHz (which extends above and below longwave transmissions). In Europe, part of the LF spectrum is used for AM broadcast service. In the western hemisphere, its main use is for aircraft beacon, navigation (LORAN), information, and weather systems. Time signal stations MSF, DCF77, JJY and WWVB are found in this band.
In the USA, the portion between 160 and 190 kHz can be used for experimental purposes and is sometimes called the "Lost Band". Unlicensed operation by the public is permitted south of 60 degrees north latitude, except where interference would occur to 10 licensed location service stations located along the coasts. Regulations for use include a power output of no more than 1 watt, and an antenna/ground-lead length of no more than 15 meters, and a field strength of no more than 4.9 microvolts/meter. Also, emissions outside of the 160–190 kHz band must be attenuated by at least 20 dB below the level of the unmodulated carrier. Amateur Radio operators experiment in this band.
A 136 kHz allocation (135.7 to 137.8 kHz) band is available in many countries in Europe, Canada, New Zealand and French overseas dependencies. Activity levels are high, especially in Europe, with a world record distance for a two-way contact of over 10,000km from near Vladivostok to New Zealand. . Most activity uses very slow computer controlled morse code or specialised digital communications modes, although there is a reasonable amount of conventional morse used when signals are strong.
The UK allocated a 2.8 kHz sliver of spectrum from 71.6 to 74.4 kHz beginning in April 1996 to UK amateurs who applied for a Notice of Variation to use the band on a noninterference basis with a maximum output power of 1 W ERP (effective radiated power). This was withdrawn on 30 June 2003 after a number of extensions in favour of the European-harmonised 136 kHz band. A 1-watt transmission of very slow Morse Code between G3AQC (in the UK) and W1TAG (in the USA) spanned the Atlantic Ocean for 3275 miles on November 21-22, 2001.
| Radio spectrum | ||||||||||
| ELF | SLF | ULF | VLF | LF | MF | HF | VHF | UHF | SHF | EHF |
| 3 Hz | 30 Hz | 300 Hz | 3 kHz | 30 kHz | 300 kHz | 3 MHz | 30 MHz | 300 MHz | 3 GHz | 30 GHz |
| 30 Hz | 300 Hz | 3 kHz | 30 kHz | 300 kHz | 3 MHz | 30 MHz | 300 MHz | 3 GHz | 30 GHz | 300 GHz |
| The Electromagnetic Spectrum (Sorted by wavelength, short to long) Gamma ray | X-ray | Ultraviolet | Visible spectrum | Infrared | Terahertz radiation | Microwave | Radio waves
Visible (optical) spectrum: Violet | Blue | Green | Yellow | Orange | Red
Microwave spectrum: W band | V band | K band: Ka band, Ku band | X band | C band | S band | L band
Radio spectrum: EHF | SHF | UHF | VHF | HF | MF | LF | VLF | ULF | SLF | ELF
Wavelength designations : Microwave | Shortwave | Mediumwave | Longwave
|
References
External articles
- Tomislav Stimac, "[Definition of frequency bands (VLF, ELF... etc.)]". IK1QFK Home Page (vlf.it).
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