Longwave
In radio, longwave, long wave or long-wave,
In contemporary usage, the term longwave is not defined precisely, and its intended meaning varies. It may be used for radio wavelengths longer than 1,000 m
In Europe, Africa, and large parts of Asia (
Propagation
Because of their long wavelength, radio waves in this frequency range can diffract over obstacles like mountain ranges and travel beyond the horizon, following the contour of the Earth. This mode of propagation, called ground wave, is the main mode in the longwave band.[7] The attenuation of signal strength with distance by absorption in the ground is lower than at higher frequencies, and falls with frequency. Low frequency ground waves can be received up to 2,000 kilometres (1,200 mi) from the transmitting antenna. Very low frequency waves below 30 kHz can be used to communicate at transcontinental distances, can penetrate saltwater to depths of hundreds of feet, and are used by the military to communicate with submerged submarines.
Low frequency waves can also occasionally travel long distances by reflecting from the
Non-broadcast use
Non-directional beacons
Time signals
There are institutional broadcast stations in the range that transmit coded time signals to radio clocks. For example:
- WWVB in Colorado, United States, on 60 kHz, 70 kW ERP
- DCF77 in Frankfurt, Germany, on 77.5 kHz, 50 kW
- JJY in Japan, on 40 & 60 kHz, 50 kW
- Taldom transmitter, Russia, 10 kW
- BPC in Shangqiu, China, 68.5 kHz, 90 kW
- Anthornin the UK, 17 kW ERP.
- ALS162 from Allouis, France, on 162 kHz, 800 kW
Longwaves travel by
Submarine communication
The militaries of the United Kingdom, Russian Federation, United States, Germany, India and Sweden use frequencies below 50 kHz to communicate with submerged submarines.
Amateur radio
In the ITU Radio Regulations the band 135.7–137.8 kHz is allocated (on a secondary basis) to Amateur radio worldwide, subject to a power limit of 1 watt EIRP. Many countries' regulators license amateurs to use it.
LowFER
In North America during the 1970s, the frequencies 167, 179, and 191 kHz were assigned to the short-lived Public Emergency Radio of the United States.
Nowadays, in the United States,
Frequencies from 472–479 kHz are available to licensed amateurs as the new 630 m band, part of the now-defunct maritime band, but this is often considered a medium wave sub-band.
Historic
Swedish station SAQ, located at the
Broadcasting
Longwave is used for broadcasting only within ITU Region 1. The long-wave broadcasters are located in Europe, North Africa and Mongolia.
Typically, a larger geographic area can be covered by a long-wave broadcast transmitter compared to a
Many countries have stopped using LW for broadcasting because of low audience figures, a lack of LW on new consumer receivers, increasing interference levels, the energy inefficiency of AM and high electricity costs at transmitters.
In 2014 and 2015 Russia closed all of its LW broadcast transmitters.[11]
As of 2024 more than half of LW frequencies are unoccupied and some of the remaining services are scheduled for closure. BBC Radio 4 (UK) announced that it will stop LW broadcasts 2024.[12]
Carrier frequencies
With the adoption of the Geneva Frequency Plan of 1975, long-wave carrier frequencies are exact multiples of 9 kHz; ranging from 153 to 279 kHz. One exception was a French-language station, Europe 1 in Germany, which retained its prior channel spacing until the long-wave service was terminated in 2019. Other exceptions are all Mongolian transmitters, which are 2 kHz above the internationally recognized channels.[clarification needed]
Until the 1970s, some long-wave stations in northern and eastern Europe and the Soviet Union operated on frequencies as high as 433 kHz.[13]
Some radio broadcasters, for instance
Long-distance reception
Because long-wave signals can travel very long distances, some
Reception of long-wave signals at distances in excess of 17,000 kilometres (11,000 mi) have been verified.[14]
List of long-wave broadcasting transmitters
See also
- Low frequency: for other uses (military, commercial and amateur) of this part of the radio spectrum (30–300 kHz)
- Radio broadcasting: AM broadcasting, BBC Radio 4, BBC Light Programme, Radio clock, Office de Radiodiffusion-Télévision Française, Warsaw radio mast, Digital Radio Mondiale, International broadcasting,
- Shipping: Global navigation satellite system, Navigation, Shipping Forecast
- Lists: Index of wave articles
- Other:
Notes
- ^ Wave length and frequency are inversely related, with lower frequencies corresponding to longer wavelengths; 300 kHz corresponds to 1,000 m.
References
- ISBN 0750698667.
- ^ a b "long wave". Macmillan Online Dictionary. Macmillan Publishers. Archived from the original on 11 August 2016. Retrieved 20 June 2016.
- ^ "long wave". Cambridge Online Dictionary. Cambridge University Press. Archived from the original on 20 August 2016. Retrieved 20 June 2016 – via Cambridge.org.
- ISBN 0750698667.
- ^ a b "About LWCA". Longwave Club of America. Archived from the original on 27 June 2016. Retrieved 20 June 2016.
- ISBN 978-81-223-1080-1.
- ISBN 0471743682.
- ^ Alan Melia, G3NYK. "Understanding LF Propagation". Radcom. 85 (9). Bedford, UK: Radio Society of Great Britain: 32.
{{cite journal}}
: CS1 maint: numeric names: authors list (link) - ^ SAQ Transmission. Archived 7 April 2015 at Wikiwix Radiostation Grimeton SAQ. Retrieved 5 April 2015.
- ^ Ground-wave propagation curves for frequencies between 10 kHz and 30 MHz. Archived 24 August 2012 at the Wayback Machine ITU-R Recommendation P.368-9
- ^ "Russia says 'So long, long-wave'". BBC News. 7 May 2018. Archived from the original on 23 February 2017. Retrieved 7 May 2018.
- ^ BBC Radio 4 begins information campaign to transition listeners from Long Wave
- ISBN 0-592-00081-8.
- ^ http://www.classaxe.com/dx/ndb/rww/stats#top Archived 16 February 2016 at the Wayback Machine
External links
- Tomislav Stimac, "Definition of frequency bands (VLF, ELF... etc.)". IK1QFK Home Page.
- The Medium Wave Circle – The premier club for MW/LW enthusiasts
- Medium Wave News – Published regularly since 1954
- Euro-African Medium Wave Guide
- Longwave Club of America
- How to receive DRM from Kalundborg longwave station
- Reception of long wave and very long wave with ferrite antennas 5–50 kHz
- Klawitter, G.; Oexner, M.; Herold, K. (2000). "8.2 Langwellenrundfunk". Langwelle und Längstwelle (in German). Meckenheim: Siebel Verlag GmbH. pp. 116–131. ISBN 3-89632-043-2.
- Busch, Heinrich (14 November 2001). "Luftschiff Graf Zeppelin LZ127". (German)
- European and Asian Longwave Stations – Medium Wave Radio
- List of long- and mediumwave transmitters with GoogleMap-Links to transmission sites