Editing Shortwave radio (section)

==Shortwave broadcasting<span class="anchor" id="shortwave_broadcasting_anchor"></span>==
[[File:Indoor shot of Pori short wave station, 1954.jpg|thumb|Transmitter room of shortwave station [[Yle]] in [[Pori]], [[Finland]], in 1954]]

* ''See [[International broadcasting]] for details on the history and practice of broadcasting to foreign audiences.''
* ''See [[List of shortwave radio broadcasters]] for a list of international and domestic shortwave radio broadcasters.''
* ''See [[Shortwave relay station]] for the actual kinds of integrated technologies used to bring high power signals to listeners.''

===Frequency allocations===
{{Main|Shortwave bands}}
The [[World Radiocommunication Conference]] (WRC), organized under the auspices of the [[International Telecommunication Union]], allocates bands for various services in conferences every few years. The last WRC took place in 2023.<ref>{{Cite web |title=WRC-23 – World Radiocommunication Conferences (WRC) |url=https://www.itu.int/wrc-23/ |access-date=2024-05-13 |language=en}}</ref>

As of WRC-97 in 1997, these bands were allocated for [[international broadcasting]]. AM shortwave broadcasting channels are allocated with a 5&nbsp;kHz separation for traditional analog audio broadcasting:
{{Clear}}
{| border="0" cellspacing="2" cellpadding="1" style="float:left;margin-left:10px"
|-
! style="background:#b5b5b5;"| Metre Band
! style="background:#b5b5b5;"| Frequency Range
! style="background:#b5b5b5;"| Remarks
|-
| 120&nbsp;m
| 2.3–2.495&nbsp;MHz
| tropical band
|- style="background:#e8e8e8;"
|| 90&nbsp;m
|| 3.2–3.4&nbsp;MHz
|| tropical band
|-
| 75&nbsp;m
| 3.9–4&nbsp;MHz
| shared with the North American [[80-meter band|amateur radio 80m band]]
|- style="background:#e8e8e8;"
|| 60&nbsp;m
|| 4.75–5.06&nbsp;MHz
|| tropical band
|-
| 49&nbsp;m
| 5.9–6.2&nbsp;MHz
| &nbsp;
|- style="background:#e8e8e8;"
||  41&nbsp;m
|| 7.2–7.6&nbsp;MHz
|| shared with the [[Amateur radio frequency allocations#40 Metres|amateur radio 40m band]]
|-
| 31&nbsp;m
| 9.4–9.9&nbsp;MHz
| the most heavily used band
|- style="background:#e8e8e8;"
|| 25&nbsp;m
|| 11.6–12.2&nbsp;MHz
|| &nbsp;
|-
| 22&nbsp;m
| 13.57–13.87&nbsp;MHz
|
|- style="background:#e8e8e8;"
|| 19&nbsp;m
|| 15.1–15.8&nbsp;MHz
|| &nbsp;
|-
| 16&nbsp;m
| 17.48–17.9&nbsp;MHz
| &nbsp;
|- style="background:#e8e8e8;"
|| 15&nbsp;m
|| 18.9–19.02&nbsp;MHz
|| almost unused, could become a DRM band
|-
| 13&nbsp;m
| 21.45–21.85&nbsp;MHz
| &nbsp;
|- style="background:#e8e8e8;"
|| 11&nbsp;m
|| 25.6–26.1&nbsp;MHz
|| may be used for local DRM broadcasting
|}
{{Clear}}
[[File:Shortwave and other bands on World Radio receiver.jpg|thumb|right|Tuning display of a cheap portable "World Radio" which includes nine shortwave bands]]
Although countries generally follow the assigned bands, there may be small differences between countries or regions. For example, in the official bandplan of the [[Netherlands]],<ref name=RijksOverheid2007/> the 49&nbsp;m band starts at 5.95&nbsp;MHz, the 41&nbsp;m band ends at 7.45&nbsp;MHz, the 11&nbsp;m band starts at 25.67&nbsp;MHz, and the 120&nbsp;m, 90&nbsp;m, and 60&nbsp;m bands are absent altogether. International broadcasters sometimes operate outside the normal the WRC-allocated bands or use off-channel frequencies. This is done for practical reasons, or to attract attention in crowded bands (60&nbsp;m, 49&nbsp;m, 40&nbsp;m, 41&nbsp;m, 31&nbsp;m, 25&nbsp;m).

The new [[digital audio broadcasting]] format for shortwave [[Digital Radio Mondiale|DRM]] operates 10&nbsp;kHz or 20&nbsp;kHz channels. There are some ongoing discussions with respect to specific band allocation for DRM, as it mainly transmitted in 10&nbsp;kHz format.

The power used by shortwave transmitters ranges from less than one watt for some experimental and amateur radio transmissions to 500 kilowatts and higher for intercontinental broadcasters and [[over-the-horizon radar]]. Shortwave transmitting centers often use specialized [[antenna (radio)|antenna]] designs (like the [[ALLISS]] antenna technology) to concentrate radio energy at the target area.

===Advantages===
[[File:Soviet SWL URS3-108-B.jpeg|thumb|right|[[Soviet Union|Soviet]] shortwave listener (A. Kozlov, URS3-108-B) in [[Borisoglebsk]], 1941]]
Shortwave possesses a number of advantages over newer technologies:
* Difficulty of censoring programming by authorities in restrictive countries. Unlike their relative ease in monitoring and [[internet censorship|censoring the Internet]], over-the air television, cable television, satellite television, satellite radio, mobile phones, landline phones, and satellite phones, government authorities face technical difficulties monitoring which stations (sites) are being listened to (accessed). For example, during the [[1991 Soviet coup d'état attempt|attempted coup]] against Soviet President [[Mikhail Gorbachev]], when his access to communications was limited (e.g. his phones, television and radio were cut off), Gorbachev was able to stay informed by means of the [[BBC World Service]] on shortwave.<ref name=w4uvh/>
* Low-cost shortwave radios are widely available in all but the most repressive countries in the world. Simple shortwave [[regenerative receiver]]s can be easily built with a few parts.
* In many countries (particularly in most developing nations and in the [[Eastern bloc]] during the [[Cold War]] era) ownership of shortwave receivers has been and continues to be widespread<ref name=Habrat_recollections/> (in many of these countries some domestic stations also used shortwave).
* Many newer shortwave receivers are portable and can be battery-operated, making them useful in difficult circumstances. Newer technology includes [[hand-cranked radio]]s which provide power without batteries.
* Shortwave radios can be used in situations where [[Terrestrial television|over-the-air television]], [[cable television]], [[satellite television]], [[Landline|landline phones]], [[mobile phones]], [[satellite phones]], [[Communications satellite|satellite communications]], or the [[Internet]] is temporarily, long-term or permanently unavailable (or unaffordable).
* Shortwave radio travels much farther than broadcast FM (88–108&nbsp;MHz). Shortwave broadcasts can be easily transmitted over a distance of several thousand miles, including from one continent to another.
* Particularly in tropical regions, SW is somewhat less prone to interference from [[thunderstorms]] than [[medium wave|medium wave radio]], and is able to cover a large geographic area with relatively low power (and hence cost). Therefore, in many of these countries it is widely used for domestic broadcasting.
* Very little infrastructure is required for long-distance two-way communications using shortwave radio. All one needs is a pair of transceivers, each with an antenna, and a source of energy (such as a battery, a portable generator, or the electrical grid). This makes shortwave radio one of the most robust means of communications, which can be disrupted only by interference or bad ionospheric conditions. Modern digital transmission modes such as [[MFSK]] and [[Olivia MFSK|Olivia]] are even more robust, allowing successful reception of signals well below the [[noise floor]] of a conventional receiver.

===Disadvantages===
Shortwave radio's benefits are sometimes regarded as being outweighed by its drawbacks, including:
* In most Western countries, shortwave radio ownership is usually limited to enthusiasts, since most new standard radios do not receive the shortwave band. Therefore, Western audiences are limited.
* In the developed world, shortwave reception is very difficult in urban areas because of excessive noise from [[Switched-mode power supply|switched-mode]] power adapters, fluorescent or LED light sources, internet modems and routers, computers and many other sources of [[radio interference]].
* Audio quality may be limited due to interference and the modes that are used.