Editing Shortwave radio (section)

{{short description|Radio transmissions using wavelengths between 10 m and 100 m}}
{{redirect|Shortwave}}
[[File:Grundig Satellit Professional 400.JPG|thumb|right|[[Grundig]] Satellit&nbsp;400 solid-state, digital [[shortwave receiver]], c.&nbsp;1986<ref name=SWRad_GS400/>]]

'''Shortwave radio''' is [[radio]] transmission using [[radio frequencies]] in the [[shortwave bands]] (SW). There is no official definition of the band range, but it always includes all of the [[High frequency|high frequency band (HF)]], which extends from 3 to 30&nbsp;MHz (approximately 100 to 10 metres in wavelength). It lies between the [[Medium frequency|medium frequency band (MF)]] and the bottom of the [[Very high frequency|VHF band]].

[[Radio wave]]s in the shortwave band can be reflected or refracted from a layer of electrically charged atoms in the atmosphere called the [[ionosphere]]. Therefore, short waves directed at an angle into the sky can be reflected back to Earth at great distances, beyond the horizon. This is called [[skywave]] or "skip" [[radio propagation|propagation]]. Thus shortwave radio can be used for communication over very long distances, in contrast to radio waves of higher frequency, which travel in straight lines ([[line-of-sight propagation]]) and are generally limited by the visual horizon, about 64&nbsp;km (40&nbsp;miles).
[[File:Tesla 623A Máj.png|thumb|Tesla Máj 623A, Short-long-medium wave tube receiver from Czechoslovakia, {{circa|1956}}/57]]

Shortwave broadcasts of radio programs played an important role in international broadcasting for many decades, serving both to provide news and information and as a [[propaganda|propaganda tool]] for an international audience. The heyday of [[International broadcasting|international shortwave broadcasting]] was during the [[Cold War]] between 1960 and 1990. 

With the wide implementation of other technologies for the long-distance distribution of radio programs, such as [[satellite radio]], [[Cable radio|cable broadcasting]] and [[Internet radio|IP-based transmissions]], shortwave broadcasting lost importance. Initiatives for the [[DRM30|digitization]] of broadcasting did not bear fruit either, and {{asof|2025|lc=yes}}, relatively few broadcasters continue to broadcast programs on shortwave.  

However, shortwave remains important in war zones, such as in the [[Russo-Ukrainian war]],<ref>{{Cite journal |date=March 25, 2022 |title=Why the BBC World Service's New Ukrainian Shortwave Service Matters |url=https://www.rand.org/pubs/commentary/2022/03/why-the-bbc-world-services-new-ukrainian-shortwave-service.html |website=The Rand Blog |last1=Sacks |first1=Benjamin J. }}</ref><ref>{{Cite web |date=February 25, 2022 |title=Ukraine: BBC adds two shortwave broadcasts, NEXUS adds MW service |url=https://swling.com/blog/2022/02/ukraine-bbc-adds-two-shortwave-broadcasts-nexus-adds-mw-service/ |website=The SW Ling Post |access-date=December 4, 2023}}</ref><ref>{{Cite web |date=February 25, 2022 |title=BBC World Service 15735 AM 1400 utc 25 Feb 2022 - new transmission |url=https://www.hfunderground.com/board/index.php/topic,93488.0.html |website=HF Underground |access-date=December 4, 2023}}</ref><ref>{{Cite web |date=March 2, 2022 |title=BBC World Service 5875 kHz Shortwave Russia Ukraine War broadcast |url=https://www.youtube.com/watch?v=nsrOzB2Cfgs |website=YouTube |access-date=December 4, 2023}}</ref><ref>{{cite news |last1=Demianyk |first1=Graeme |title=BBC Revives Old-School Radio Service To Help Ukraine As TV And Internet Attacked |url=https://www.huffingtonpost.co.uk/entry/bbc-ukraine-shortwave-radio-frequencies_uk_621fa132e4b0a7784bb2808f/ |access-date=11 December 2023 |work=HuffPost UK |date=2 March 2022 |language=en}}</ref> and shortwave broadcasts can be transmitted over thousands of miles from a single transmitter, making it difficult for government authorities to censor them. Shortwave radio is also often used by aircraft.