Shortwave bands
Encyclopedia
Shortwave bands are frequency allocations for use within the shortwave
radio spectrum (the upper MF
band and all of the HF
band). They are the primary medium for applications such as maritime communications, international broadcasting and worldwide amateur radio
activity because they take advantage of ionospheric skip propagation
to send data around the world. The bands are conventionally stated in wavelength
, measured in metres. Propagation
behavior on the shortwave bands depends on the time of day, the season and the level of solar activity
.
with 5-kHz steps between channels; a few use single sideband modulation.
The World Radiocommunication Conference
(WRC), organized under the auspices of the International Telecommunication Union
, allocates bands for various services in periodic conferences. The last WRC took place in 2007.
At WRC-97 in 1997, the following bands were allocated for international broadcasting
:
is an educational hobby and can be useful for emergency communications, especially in remote regions or disaster areas.
.
Most countries with HF citizens'-band
allocations use 40 or 80 channels between approximately 26.6 MHz and 27.5 MHz, in 10- or 12.5-kHz steps. Part of the 11m/27-MHz band was also allocated in many countries for early-model cordless phones. Due to antenna-length requirements and the band's long-distance propagation characteristics (undesirable in these cases), much land-mobile radio
activity has moved to VHF or UHF and most cordless-phone use is at UHF or higher. Some segments of the HF spectrum are allocated for fixed services, providing point-to-point communication between sites with no access to wired communications.
Similar rules exist in Europe, where it has become necessary for European amateurs to police the bands due to overcrowding. Most military HF band incursions into the HF ham bands occur in Europe or Africa. Since the end of the Cold War
specific military HF allocations have gradually disappeared from the HF bands, except for Africa and some parts of Asia. In Australia, the military shares the HF bands with civilian users; this is mainly due to low population density and relative under-use of the HF bands. The military in the Americas and Australia has tended to use the civilian fixed, maritime mobile and aeronautical mobile allocations on an ad hoc (non-interference) basis.
, space research (FCC terminology) and standard- frequency-and-time services. RF diathermy
equipment uses 27.12 MHz to heat bulk materials or adhesives for the purpose of drying or improving curing
. The industrial use of the frequency suggested the use of the 11m band for CB radio. About a dozen narrow ("sliver") allocations for ISM exist throughout the radio spectrum. These allocations are among the smallest in the HF band, with respect to national HF allocations.
Shortwave
Shortwave radio refers to the upper MF and all of the HF portion of the radio spectrum, between 1,800–30,000 kHz. Shortwave radio received its name because the wavelengths in this band are shorter than 200 m which marked the original upper limit of the medium frequency band first used...
radio spectrum (the upper MF
Medium frequency
Medium frequency refers to radio frequencies in the range of 300 kHz to 3 MHz. Part of this band is the medium wave AM broadcast band. The MF band is also known as the hectometer band or hectometer wave as the wavelengths range from ten down to one hectometers...
band and all of the HF
High frequency
High frequency radio frequencies are between 3 and 30 MHz. Also known as the decameter band or decameter wave as the wavelengths range from one to ten decameters . Frequencies immediately below HF are denoted Medium-frequency , and the next higher frequencies are known as Very high frequency...
band). They are the primary medium for applications such as maritime communications, international broadcasting and worldwide amateur radio
Amateur radio
Amateur radio is the use of designated radio frequency spectrum for purposes of private recreation, non-commercial exchange of messages, wireless experimentation, self-training, and emergency communication...
activity because they take advantage of ionospheric skip propagation
Skywave
Skywave is the propagation of electromagnetic waves bent back to the Earth's surface by the ionosphere. As a result of skywave propagation, a broadcast signal from a distant AM broadcasting station at night, or from a shortwave radio station can sometimes be heard as clearly as local...
to send data around the world. The bands are conventionally stated in wavelength
Wavelength
In physics, the wavelength of a sinusoidal wave is the spatial period of the wave—the distance over which the wave's shape repeats.It is usually determined by considering the distance between consecutive corresponding points of the same phase, such as crests, troughs, or zero crossings, and is a...
, measured in metres. Propagation
Radio propagation
Radio propagation is the behavior of radio waves when they are transmitted, or propagated from one point on the Earth to another, or into various parts of the atmosphere...
behavior on the shortwave bands depends on the time of day, the season and the level of solar activity
Solar cycle
The solar cycle, or the solar magnetic activity cycle, is a periodic change in the amount of irradiation from the Sun that is experienced on Earth. It has a period of about 11 years, and is one component of solar variation, the other being aperiodic fluctuations. Solar variation causes changes in...
.
International broadcast bands
The bands and frequencies below are derived from multiple sources, and different radios may have different frequency numbers. Most international broadcasters use amplitude modulationAmplitude modulation
Amplitude modulation is a technique used in electronic communication, most commonly for transmitting information via a radio carrier wave. AM works by varying the strength of the transmitted signal in relation to the information being sent...
with 5-kHz steps between channels; a few use single sideband modulation.
The World Radiocommunication Conference
World Radiocommunication Conference
World Radiocommunication Conference is organized by ITU to review, and, as necessary, revise the Radio Regulations, the international treaty governing the use of the radio-frequency spectrum and the geostationary-satellite and non-geostationary-satellite orbits. It is held every three to four years...
(WRC), organized under the auspices of the International Telecommunication Union
International Telecommunication Union
The International Telecommunication Union is the specialized agency of the United Nations which is responsible for information and communication technologies...
, allocates bands for various services in periodic conferences. The last WRC took place in 2007.
At WRC-97 in 1997, the following bands were allocated for international broadcasting
International broadcasting
International broadcasting is broadcasting that is deliberately aimed at a foreign, rather than a domestic, audience. It usually is broadcast by means of longwave, mediumwave, or shortwave radio, but in recent years has also used direct satellite broadcasting and the Internet as means of reaching...
:
| Band | Frequency Range | Remarks |
|---|---|---|
| 120 m | 2300 - 2495 kHz | Tropical (regional) band |
| 90m | 3200–3400 kHz | Tropical band |
| 75 m | 3900–4000 kHz | Shared with the North American amateur radio Amateur radio Amateur radio is the use of designated radio frequency spectrum for purposes of private recreation, non-commercial exchange of messages, wireless experimentation, self-training, and emergency communication... 80m band |
| 60m | 4750–5060 kHz | Tropical band |
| 49m | 5900–6200 kHz | |
| 41m | 7200–7450 kHz | Shared with the amateur radio Amateur radio Amateur radio is the use of designated radio frequency spectrum for purposes of private recreation, non-commercial exchange of messages, wireless experimentation, self-training, and emergency communication... 40m band |
| 31m | 9400–9900 kHz | Most heavily-used band |
| 25m | 11,600–12,100 kHz | |
| 22m | 13,570–13,870 kHz | Substantially used in Eurasia |
| 19m | 15,100–15,800 kHz | |
| 16m | 17,480–17,900 kHz | |
| 15m | 18,900–19,020 kHz | Lightly utilized; may become DRM Digital Radio Mondiale Digital Radio Mondiale is a set of digital audio broadcasting technologies designed to work over the bands currently used for AM broadcasting, particularly shortwave... band in future |
| 13m | 21,450–21,850 kHz | |
| 11m | 25,600–26,100 kHz | May be used for local DRM broadcasting |
- 120m band – Mostly used locally in tropical regions, with time stations at 2500 kHz. Although this is regarded as shortwaveShortwaveShortwave radio refers to the upper MF and all of the HF portion of the radio spectrum, between 1,800–30,000 kHz. Shortwave radio received its name because the wavelengths in this band are shorter than 200 m which marked the original upper limit of the medium frequency band first used...
, it is in the MFMedium frequencyMedium frequency refers to radio frequencies in the range of 300 kHz to 3 MHz. Part of this band is the medium wave AM broadcast band. The MF band is also known as the hectometer band or hectometer wave as the wavelengths range from ten down to one hectometers...
band. - 90m band – Mostly used locally in tropical regions, with limited long-distance reception at night
- 75m band – Mostly used in the Eastern HemisphereEastern HemisphereThe Eastern Hemisphere, also Eastern hemisphere or eastern hemisphere, is a geographical term for the half of the Earth that is east of the Prime Meridian and west of 180° longitude. It is also used to refer to Europe, Asia, Africa, and Australasia, vis-à-vis the Western Hemisphere, which includes...
; not widely received in North and South America - 60m band – Mostly used locally in tropical regionsTropicsThe tropics is a region of the Earth surrounding the Equator. It is limited in latitude by the Tropic of Cancer in the northern hemisphere at approximately N and the Tropic of Capricorn in the southern hemisphere at S; these latitudes correspond to the axial tilt of the Earth...
, although widely usable at night. Time stations use 5000 kHz. - 49m band – Good year-round night band; daytime reception poor
- 41m band – Reception varies by region – reasonably good night reception, but few transmitters in this band target North America. According to the WRC-03 Decisions on HF broadcasting, in International Telecommunication Union regions 1 and 3, the segment 7100–7200 kHz is reserved for amateur radio use and there are no new broadcasting allocations in this portion of the band. 7350–7400 kHz is newly allocated; in Regions 1 and 3, 7400–7450 kHz was also allocated effective March 29, 2009.
- 31m band – Good year-round night band; seasonal during the day, with best reception in winter. Time stations are clustered around 10 MHz.
- 25m band – Generally best during summer and the period before and after sunset year-round
- 22m band – Similar to the 19m band; best in summer
- 19m band – Day reception good, night reception variable; best during summer. Time stationsTime signalA time signal is a visible, audible, mechanical, or electronic signal used as a reference to determine the time of day.-Audible and visible time signals:...
such as WWV use 15 MHz. - 16m band – Day reception good; night reception varies seasonally, with summer best.
- 15m band – Seldom used
- 13m band – Erratic daytime reception, with very little night reception. Similar to 11 metres, but long-distance daytime broadcasting keeps this band active in the Asia-Pacific region.
- 11m band – Seldom used. Daytime reception poor low in the solar cycle, but potentially excellent when the solar cycle (generally indicated by the number of sunspotsWolf numberThe Wolf number is a quantity that measures the number of sunspots and groups of sunspots present on the surface of the sun....
) is high. Nighttime reception nonexistent, except for local groundwaveSurface waveIn physics, a surface wave is a mechanical wave that propagates along the interface between differing media, usually two fluids with different densities. A surface wave can also be an electromagnetic wave guided by a refractive index gradient...
propagation. Digital Radio MondialeDigital Radio MondialeDigital Radio Mondiale is a set of digital audio broadcasting technologies designed to work over the bands currently used for AM broadcasting, particularly shortwave...
has proposed that this band be used for local digital shortwave broadcasts, testing the concept in Mexico CityMexico CityMexico City is the Federal District , capital of Mexico and seat of the federal powers of the Mexican Union. It is a federal entity within Mexico which is not part of any one of the 31 Mexican states but belongs to the federation as a whole...
in 20052005 in radioThe year 2005 in radio involved some significant events.-Events:*April 29 - KFRC 610 AM in San Francisco, switches formats as a result of ownership change. KFRC becomes KEAR, the "Sound of the New Life", a listener-supported, gospel/religious only station. It had been previously KFRC from...
. The Citizens' BandCitizens' band radioCitizens' Band radio is, in many countries, a system of short-distance radio communications between individuals on a selection of 40 channels within the 27-MHz band. Citizens' Band is distinct from the FRS, GMRS, MURS and amateur radio...
allocation in most countries is within this band.
Amateur HF bands
Amateur radio operators in many countries are allocated specific shortwave bands for private, non-commercial use. Amateur radioAmateur radio
Amateur radio is the use of designated radio frequency spectrum for purposes of private recreation, non-commercial exchange of messages, wireless experimentation, self-training, and emergency communication...
is an educational hobby and can be useful for emergency communications, especially in remote regions or disaster areas.
Marine, air, land mobile and fixed allocations
Designated bands in the shortwave spectrum are used for ships, aircraft, and land vehicles. Shortwave (HF radio) is used by transoceanic aircraft for communications with air-traffic control centers out of VHF radio rangeRadio propagation
Radio propagation is the behavior of radio waves when they are transmitted, or propagated from one point on the Earth to another, or into various parts of the atmosphere...
.
Most countries with HF citizens'-band
Citizens' band radio
Citizens' Band radio is, in many countries, a system of short-distance radio communications between individuals on a selection of 40 channels within the 27-MHz band. Citizens' Band is distinct from the FRS, GMRS, MURS and amateur radio...
allocations use 40 or 80 channels between approximately 26.6 MHz and 27.5 MHz, in 10- or 12.5-kHz steps. Part of the 11m/27-MHz band was also allocated in many countries for early-model cordless phones. Due to antenna-length requirements and the band's long-distance propagation characteristics (undesirable in these cases), much land-mobile radio
Land Mobile Radio System
Land Mobile Radio System is a term that denotes a wireless communications system intended for use by terrestrial users in vehicles or on foot . Such systems are used by emergency first responder organizations, public works organizations, or companies with large vehicle fleets or numerous field...
activity has moved to VHF or UHF and most cordless-phone use is at UHF or higher. Some segments of the HF spectrum are allocated for fixed services, providing point-to-point communication between sites with no access to wired communications.
Military HF use
In the US and Canada, as well as the Americas (ITU Region 2) as a whole, there are no pre-designated HF allocations for military use.Similar rules exist in Europe, where it has become necessary for European amateurs to police the bands due to overcrowding. Most military HF band incursions into the HF ham bands occur in Europe or Africa. Since the end of the Cold War
Cold War
The Cold War was the continuing state from roughly 1946 to 1991 of political conflict, military tension, proxy wars, and economic competition between the Communist World—primarily the Soviet Union and its satellite states and allies—and the powers of the Western world, primarily the United States...
specific military HF allocations have gradually disappeared from the HF bands, except for Africa and some parts of Asia. In Australia, the military shares the HF bands with civilian users; this is mainly due to low population density and relative under-use of the HF bands. The military in the Americas and Australia has tended to use the civilian fixed, maritime mobile and aeronautical mobile allocations on an ad hoc (non-interference) basis.
Industrial/Scientific/Medical (ISM) and other HF allocations
Above 10 MHz there are numerous frequencies set aside for radio astronomyRadio astronomy
Radio astronomy is a subfield of astronomy that studies celestial objects at radio frequencies. The initial detection of radio waves from an astronomical object was made in the 1930s, when Karl Jansky observed radiation coming from the Milky Way. Subsequent observations have identified a number of...
, space research (FCC terminology) and standard- frequency-and-time services. RF diathermy
Diathermy
In the natural sciences, the term diathermy means "electrically induced heat" and is commonly used for muscle relaxation. It is also a method of heating tissue electromagnetically or ultrasonically for therapeutic purposes in medicine.-Surgical uses:...
equipment uses 27.12 MHz to heat bulk materials or adhesives for the purpose of drying or improving curing
Curing (chemistry)
Curing is a term in polymer chemistry and process engineering that refers to the toughening or hardening of a polymer material by cross-linking of polymer chains, brought about by chemical additives, ultraviolet radiation, electron beam or heat...
. The industrial use of the frequency suggested the use of the 11m band for CB radio. About a dozen narrow ("sliver") allocations for ISM exist throughout the radio spectrum. These allocations are among the smallest in the HF band, with respect to national HF allocations.
See also
- ShortwaveShortwaveShortwave radio refers to the upper MF and all of the HF portion of the radio spectrum, between 1,800–30,000 kHz. Shortwave radio received its name because the wavelengths in this band are shorter than 200 m which marked the original upper limit of the medium frequency band first used...
- High frequencyHigh frequencyHigh frequency radio frequencies are between 3 and 30 MHz. Also known as the decameter band or decameter wave as the wavelengths range from one to ten decameters . Frequencies immediately below HF are denoted Medium-frequency , and the next higher frequencies are known as Very high frequency...
- Medium frequencyMedium frequencyMedium frequency refers to radio frequencies in the range of 300 kHz to 3 MHz. Part of this band is the medium wave AM broadcast band. The MF band is also known as the hectometer band or hectometer wave as the wavelengths range from ten down to one hectometers...
(for the unique case of the 120m band) - International broadcastingInternational broadcastingInternational broadcasting is broadcasting that is deliberately aimed at a foreign, rather than a domestic, audience. It usually is broadcast by means of longwave, mediumwave, or shortwave radio, but in recent years has also used direct satellite broadcasting and the Internet as means of reaching...
- World Radiocommunication ConferenceWorld Radiocommunication ConferenceWorld Radiocommunication Conference is organized by ITU to review, and, as necessary, revise the Radio Regulations, the international treaty governing the use of the radio-frequency spectrum and the geostationary-satellite and non-geostationary-satellite orbits. It is held every three to four years...
- World Administrative Radio ConferenceWorld Administrative Radio ConferenceThe World Administrative Radio Conference was a technical conference of the International Telecommunications Union where delegates from member nations of the ITU met to revise or amend the entire international Radio Regulations pertaining to all telecommunication services throughout the world...
External links
- American Radio Relay League -- the United States lobbying body for amateur radioAmateur radioAmateur radio is the use of designated radio frequency spectrum for purposes of private recreation, non-commercial exchange of messages, wireless experimentation, self-training, and emergency communication...
and the body responsible for the ARRL Handbook - Radio Amateurs of Canada -- Canada's National Amateur Radio Society
- World Radio and Television Handbook
- EiBi & DX - Complete list of International Broadcasting Stations worldwide, frequently updated.
- UnwantedEmissions.com - Radio spectrum allocations reference.