Editing Shortwave radio (section)

==Users==
[[File:Shortwave_Radio_Dial.jpg|thumb|right|Portable shortwave receiver's [[digital display]] tuned to the [[80-meter band|75&ndash;meter band]]]]
Some established users of the shortwave radio bands may include:
* [[International broadcasting]] primarily by government-sponsored [[propaganda]], or international news (for example, the [[BBC World Service]]), religious or cultural stations to foreign audiences: The most common use of all.
* Domestic broadcasting: to widely dispersed populations with few [[longwave]], [[mediumwave]] and FM stations serving them; or for speciality political, religious and [[alternative media]] networks; or of individual commercial and non-commercial paid broadcasts.
* Oceanic [[air traffic control]] uses the HF/shortwave band for long-distance communication to aircraft over the oceans and poles, which are far beyond the range of traditional [[VHF]] frequencies. Modern systems also include satellite communications, such as ADS-C/[[CPDLC]].
* Two-way radio communications by marine and maritime HF stations, aeronautical users, and ground based stations.<ref name="Ilčev">{{cite book |last1=Ilčev |first1=Stojče Dimov |title=Global Aeronautical Distress and Safety Systems (GADSS): Theory and Applications |url=https://books.google.com/books?id=SWvDDwAAQBAJ&q=shortwave+communications+users&pg=PA310 |date=10 December 2019 |publisher=Springer Nature |isbn=9783030306328 |access-date=9 September 2021 |archive-date=25 January 2022 |archive-url=https://web.archive.org/web/20220125091407/https://books.google.com/books?id=SWvDDwAAQBAJ&q=shortwave+communications+users&pg=PA310 |url-status=live }}</ref> For example, two way shortwave communication is still used in remote regions by the [[Royal Flying Doctor Service of Australia]].<ref name="Berg4">{{cite book |last1=Berg |first1=Jerome S. |title=The Early Shortwave Stations: A Broadcasting History Through 1945 |url=https://books.google.com/books?id=XSWXAAAAQBAJ&q=flying+doctors+australia+shortwave&pg=PA162 |date=20 September 2013 |publisher=McFarland |isbn=9780786474110 |access-date=9 September 2021 |archive-date=25 January 2022 |archive-url=https://web.archive.org/web/20220125091416/https://books.google.com/books?id=XSWXAAAAQBAJ&q=flying+doctors+australia+shortwave&pg=PA162 |url-status=live }}</ref>
* [[Utility station|"Utility" stations]] transmitting messages not intended for the general public, such as merchant shipping, marine weather, and ship-to-shore stations; for aviation weather and air-to-ground communications; for military communications; for long-distance governmental purposes, and for other non-broadcast communications.
* [[Amateur radio]] operators at the [[80-meter band|80/75]], [[60-meter band|60]], [[40-meter band|40]], [[30-meter band|30]], [[20-meter band|20]], [[17-meter band|17]], [[15-meter band|15]], [[12-meter band|12]], and [[10-meter band|10&ndash;meter]] bands. Licenses are granted by authorized government agencies.
* [[Time signal]] and [[radio clock]] stations: In North America, [[WWV (radio station)|WWV radio]] and [[WWVH|WWVH radio]] transmit at these frequencies: 2.5&nbsp;MHz, 5&nbsp;MHz, 10&nbsp;MHz, and 15&nbsp;MHz; and WWV also transmits on 20&nbsp;MHz. The [[CHU (radio station)|CHU radio station]] in Canada transmits on the following frequencies: 3.33&nbsp;MHz, 7.85&nbsp;MHz, and 14.67&nbsp;MHz. Other similar [[radio clock]] stations transmit on various shortwave and longwave frequencies around the world. The shortwave transmissions are primarily intended for human reception, while the longwave stations are generally used for automatic synchronization of watches and clocks.

Sporadic or non-traditional users of the shortwave bands may include:
* [[Clandestine radio|Clandestine stations]]. These are stations that broadcast on behalf of various political movements such as rebel or insurrectionist forces. They may advocate civil war, insurrection, rebellion against the government-in-charge of the country to which they are directed. Clandestine broadcasts may emanate from transmitters located in rebel-controlled territory or from outside the country entirely, using another country's transmission facilities.<ref name=Sterling2004/>
* [[Numbers station]]s. These stations regularly appear and disappear all over the shortwave radio band, but are unlicensed and untraceable. It is believed that numbers stations are operated by government agencies and are used to communicate with clandestine operatives working within foreign countries. However, no definitive proof of such use has emerged. Because the vast majority of these broadcasts contain nothing but the recitation of blocks of numbers, in various languages, with occasional bursts of music, they have become known colloquially as "number stations". Perhaps the most noted number station is called the [[Lincolnshire Poacher (numbers station)|"Lincolnshire Poacher"]], named after the 18th&nbsp;century English folk song, which is transmitted just before the sequences of numbers.
* Unlicensed [[two way radio]] activity by individuals such as taxi drivers, bus drivers and fishermen in various countries can be heard on various shortwave frequencies. Such unlicensed transmissions by "pirate" or "bootleg" two way radio operators<ref name=PopMech1940Jan/> can often cause [[Co-channel interference|signal interference]] to licensed stations.  Unlicensed business radio (taxis, trucking companies, among numerous others) land mobile systems may be found in the 20-30&nbsp;MHz region while unlicensed marine mobile and other similar users may be found over the entire shortwave range.<ref name=IARU/>
* [[Pirate radio]] broadcasters who feature programming such as music, talk and other entertainment, can be heard sporadically and in various modes on the shortwave bands. Pirate broadcasters take advantage of the better propagation characteristics to achieve more range compared to the AM or FM broadcast bands.<ref name="Yoder2002">{{cite book |first=Andrew R. |last=Yoder |title=Pirate Radio Stations: Tuning in to underground broadcasts in the Air and Online |url=https://books.google.com/books?id=qMjT5wOX-d4C |year=2002 |publisher=McGraw Hill Professional |isbn=978-0-07-137563-4 |access-date=2017-11-28 |archive-date=2020-08-19 |archive-url=https://web.archive.org/web/20200819202519/https://books.google.com/books?id=qMjT5wOX-d4C |url-status=live }}</ref>
* [[Over-the-horizon radar]]: From 1976 to 1989, the [[Soviet Union]]'s [[Duga radar|Russian Woodpecker]] over-the-horizon radar system blotted out numerous shortwave broadcasts daily.
* [[Ionospheric heater]]s used for scientific experimentation such as the [[High Frequency Active Auroral Research Program]] in Alaska, and the [[Sura Ionospheric Heating Facility|Sura ionospheric heating facility]] in Russia.<ref name=BychkovGolubkov2010/>