Shortwave bands

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Shortwave bands are frequency allocations for use within the shortwave radio spectrum (the upper medium frequency [MF] band and all of the high frequency [HF] band). Radio waves in these frequency ranges can be used for very long distance (transcontinental) communication because they can reflect off layers of charged particles in the ionosphere and return to Earth beyond the horizon, a mechanism called skywave or “skip” propagation. They are allocated by the ITU for radio services such as maritime communications, international shortwave broadcasting and worldwide amateur radio. The bands are conventionally named by their wavelength in metres, for example the ‘20 meter band’. Radio propagation and possible communication distances vary depending on the time of day, the season and the level of solar activity.

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International broadcast bands

These bands are used by powerful long range AM radio stations, many operated by governments, which broadcast to multiple countries. Most international broadcasters use amplitude modulation with 5 kHz steps between channels; a few use single sideband or reduced carrier single sideband modulation. [1] The World Radiocommunication Conference (WRC), organized under the auspices of the International Telecommunication Union, allocates bands for various services in periodic conferences. The most recent WRC took place in 2012. At WRC-97 in 1997, the following bands were allocated for international broadcasting:

BandFrequency range (MHz)Remarks
120 m
2.3–2.495
Mostly used locally in tropical regions, with time stations at 2.5 MHz. Although this is regarded as shortwave, it is a MF band.
90 m
3.2–3.4
Mostly used locally in tropical regions, with limited long-distance reception at night. A notable example of a station using this band is Canadian time station CHU on 3.33 MHz.
75 m
3.9–4
Mostly used in the Eastern Hemisphere after dark; not widely received in North and South America. Shared with the North American amateur radio 80 m band.
60 m
4.75–4.995
Mostly used locally in tropical regions, especially Brazil, although widely usable at night. Time stations use 5 MHz.
49 m
5.9–6.2
Good year-round night band; daytime (long distance) reception poor
41 m
7.2–7.45
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, [2] in International Telecommunication Union regions 1 and 3, the segment 7.1–7.2 MHz is reserved for amateur radio use and there are no new broadcasting allocations in this portion of the band. 7.35–7.4 MHz is newly allocated; in Regions 1 and 3, 7.4–7.45 MHz was also allocated effective March 29, 2009. In Region 2, 7.2–7.3 MHz is part of the amateur radio 40 m band.
31 m
9.4–9.9
Most heavily used band. Good year-round night band; seasonal during the day, with best reception in winter. Time stations are clustered around 10 MHz.
25 m
11.6–12.1
Generally best during summer and the period before and after sunset year-round
22 m
13.57–13.87
Substantially used in Eurasia. Similar to the 19 m band; best in summer.
19 m
15.1–15.83
Day reception good, night reception variable; best during summer. Time stations such as WWV use 15 MHz.
16 m
17.48–17.9
Day reception good; night reception varies seasonally, with summer best.
15 m
18.9–19.02
Lightly utilized; may become a Digital Radio Mondiale (DRM) band in future
13 m
21.45–21.85
Erratic daytime reception, with very little night reception. Similar to 11 metres, but long-distance daytime broadcasting (best on north–south paths) keeps this band active in the Asia-Pacific region.
11 m
25.67–26.1
Seldom used. Daytime reception is poor in the low solar cycle, but potentially excellent when the solar cycle (generally indicated by the number of sunspots) is high. Nighttime reception nonexistent, except for local groundwave propagation. DRM has proposed that this band be used for local digital shortwave broadcasts, testing the concept in Mexico City in 2005. Citizens band (CB) allocation in most countries, is slightly higher in frequency than the broadcasting 11m band. There are reports of pirate CB radio users operating equipment on frequencies as low as 25.615 MHz. In the United States, this band is also shared with remote pickup units (RPUs), from 25.87 to 26.1 MHz in FM mode.

Particularly in the United States and at frequencies under 10 MHz, shortwave broadcasters may operate in between those bands, with the 60-meter band extending as high as 5.13 MHz, the 49-meter band down to 5.8 MHz, the 41-meter band as high as 7.78 MHz and the 31-meter band extending as low as 9.265 MHz. As recently as 2020, WWRB operated 90-meter stations at 3.185 and 3.195 MHz.

Amateur HF bands

Amateur radio operators in many countries are allocated several shortwave bands for private, non-commercial use. Amateur radio is a communications service, educational tool and hobby. It is particularly useful in providing emergency communication where standard telecommunications infrastructure is compromised or nonexistent, such as a disaster area or remote region of the globe.

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 range. Most countries with HF citizens'-band allocations use 40 or 80 channels between approximately 26.5 MHz and 27.9 MHz, in 10 kHz steps.

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.

Illegal "freeband" CB activity can be heard from 25 to 28 MHz, steps with operators generally using AM below 26.965 (US and European CB channel 1) and SSB above 27.405 (US and European CB channel 40). CB radio in the UK can be heard from 27.60125 to 27.99125 MHz in 10 kHz steps as well as the lower 26.965 to 27.405 MHz allocation.

The UK and Ireland both operate Community Audio Distribution (CADS) in the UK or Wireless Public Address System (WPAS) in Ireland services in the 27.600 to 27.995 MHz portion, AM and FM mode, with two overlapping sets of 40 channels (27.60125 to 27.99125 MHz in 10 kHz steps, and 27.605 to 27.995 MHz in 10 kHz steps). [3] These transmissions are usually rebroadcasts of church services and can sometimes be heard hundreds or even thousands of km (miles). Part of the 11 m/27 MHz band was also allocated in many countries for early-model cordless phones.

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 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 astronomy, 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 11 m 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

Related Research Articles

<span class="mw-page-title-main">Shortwave radio</span> Radio transmissions using wavelengths between 10 m and 100 m

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 band (HF), which extends from 3 to 30 MHz ; above the medium frequency band (MF), to the bottom of the VHF band.

<span class="mw-page-title-main">Very high frequency</span> Electromagnetic wave range of 30-300 MHz

Very high frequency (VHF) is the ITU designation for the range of radio frequency electromagnetic waves from 30 to 300 megahertz (MHz), with corresponding wavelengths of ten meters to one meter. Frequencies immediately below VHF are denoted high frequency (HF), and the next higher frequencies are known as ultra high frequency (UHF).

<span class="mw-page-title-main">Citizens band radio</span> Land mobile radio system

Citizens band radio is a land mobile radio system, a system allowing short-distance one-to-many bidirectional voice communication among individuals, using two-way radios operating near 27 MHz in the high frequency or shortwave band. Citizens band is distinct from other personal radio service allocations such as FRS, GMRS, MURS, UHF CB and the Amateur Radio Service. In many countries, CB operation does not require a license and may be used for business or personal communications.

<span class="mw-page-title-main">Ultra high frequency</span> Electromagnetic spectrum 300–3000 MHz

Ultra high frequency (UHF) is the ITU designation for radio frequencies in the range between 300 megahertz (MHz) and 3 gigahertz (GHz), also known as the decimetre band as the wavelengths range from one meter to one tenth of a meter. Radio waves with frequencies above the UHF band fall into the super-high frequency (SHF) or microwave frequency range. Lower frequency signals fall into the VHF or lower bands. UHF radio waves propagate mainly by line of sight; they are blocked by hills and large buildings although the transmission through building walls is strong enough for indoor reception. They are used for television broadcasting, cell phones, satellite communication including GPS, personal radio services including Wi-Fi and Bluetooth, walkie-talkies, cordless phones, satellite phones, and numerous other applications.

<span class="mw-page-title-main">Medium frequency</span> The range 300-3000 kHz of the electromagnetic spectrum

Medium frequency (MF) is the ITU designation for radio frequencies (RF) in the range of 300 kilohertz (kHz) to 3 megahertz (MHz). Part of this band is the medium wave (MW) AM broadcast band. The MF band is also known as the hectometer band as the wavelengths range from ten to one hectometers. Frequencies immediately below MF are denoted as low frequency (LF), while the first band of higher frequencies is known as high frequency (HF). MF is mostly used for AM radio broadcasting, navigational radio beacons, maritime ship-to-shore communication, and transoceanic air traffic control.

<span class="mw-page-title-main">High frequency</span> The range 3-30 MHz of the electromagnetic spectrum

High frequency (HF) is the ITU designation for the range of radio frequency electromagnetic waves between 3 and 30 megahertz (MHz). It is also known as the decameter band or decameter wave as its wavelengths range from one to ten decameters. Frequencies immediately below HF are denoted medium frequency (MF), while the next band of higher frequencies is known as the very high frequency (VHF) band. The HF band is a major part of the shortwave band of frequencies, so communication at these frequencies is often called shortwave radio. Because radio waves in this band can be reflected back to Earth by the ionosphere layer in the atmosphere – a method known as "skip" or "skywave" propagation – these frequencies are suitable for long-distance communication across intercontinental distances and for mountainous terrains which prevent line-of-sight communications. The band is used by international shortwave broadcasting stations (3.95–25.82 MHz), aviation communication, government time stations, weather stations, amateur radio and citizens band services, among other uses.

<span class="mw-page-title-main">Digital Radio Mondiale</span> Digital radio broadcasting standard

Digital Radio Mondiale is a set of digital audio broadcasting technologies designed to work over the bands currently used for analogue radio broadcasting including AM broadcasting—particularly shortwave—and FM broadcasting. DRM is more spectrally efficient than AM and FM, allowing more stations, at higher quality, into a given amount of bandwidth, using xHE-AAC audio coding format. Various other MPEG-4 codecs and Opus are also compatible, but the standard now specifies xHE-AAC.

The radio spectrum is the part of the electromagnetic spectrum with frequencies from 3 Hz to 3,000 GHz (3 THz). Electromagnetic waves in this frequency range, called radio waves, are widely used in modern technology, particularly in telecommunication. To prevent interference between different users, the generation and transmission of radio waves is strictly regulated by national laws, coordinated by an international body, the International Telecommunication Union (ITU).

<span class="mw-page-title-main">6-meter band</span>

The 6-meter band is the lowest portion of the very high frequency (VHF) radio spectrum internationally allocated to amateur radio use. The term refers to the average signal wavelength of 6 meters.

160-meter band refers to the band of radio frequencies between 1.8 and 2 MHz, just above the medium wave broadcast band. For many decades the lowest radio frequency band allocated for use by amateur radio, before the adoption, at the beginning of the 21st century in most countries, of the 630- and 2200-meter bands. Amateur operators often refer to 160 meters as the Top Band It is also sometimes nicknamed the "Gentleman's Band" in contrast to the often-freewheeling activity in the 80-, 40- and 20-meter bands.

LowFER refers to experimental radio communication practiced by hobbyists on frequencies below 300 kHz, a part of the radio spectrum known as low frequency. The practitioners are known as "LowFERs".

The 80 meter or 3.5 MHz band is a span of radio frequencies allocated for amateur use, from 3.5–4.0 MHz in North and South America ; generally 3.5–3.8 MHz in Europe, Africa, and northern Asia (Region 1); and 3.5–3.9 MHz in south and east Asia and the eastern Pacific (Region 3). The upper portion of the band, which is usually used for phone (voice), is sometimes referred to as 75 meters; however, in Europe, "75 m" is used to name an overlapping shortwave broadcast band between 3.9–4.0 MHz used by a number of national radio services.

<span class="mw-page-title-main">40-meter band</span> Radio frequency range allocated to amateur use

The 40-meter or 7-MHz band is an amateur radio frequency band, spanning 7.000-7.300 MHz in ITU Region 2, and 7.000-7.200 MHz in Regions 1 & 3. It is allocated to radio amateurs worldwide on a primary basis; however, only 7.000-7.200 MHz is exclusively allocated to amateur radio worldwide. Shortwave broadcasters and land mobile users also have primary allocations in some countries, and amateur stations must share the band with these users.

The 10-meter band is a portion of the shortwave radio spectrum internationally allocated to amateur radio and amateur satellite use on a primary basis. The band consists of frequencies stretching from 28.000 to 29.700 MHz.

<span class="mw-page-title-main">60-meter band</span> Amateur radio frequency band

The 60-meter band or 5 MHz band is a relatively new amateur radio allocation, first introduced in 2002, that was originally only available in a few countries, such as the United States, United Kingdom, Norway, Finland, Denmark, Ireland and Iceland. Over a number of years however, an increasing proportion of countries' telecommunications administrations – together with their government and military users – have permitted Amateur Radio operation in the 5 MHz area on a short or longer-term basis, ranging from discrete channels to a frequency band allocation.

Amateur radio frequency allocation is done by national telecommunication authorities. Globally, the International Telecommunication Union (ITU) oversees how much radio spectrum is set aside for amateur radio transmissions. Individual amateur stations are free to use any frequency within authorized frequency ranges; authorized bands may vary by the class of the station license.

The World Administrative Radio Conference (WARC) bands are three portions of the shortwave radio spectrum used by licensed and/or certified amateur radio operators. They consist of 30 meters (10.1–10.15 MHz), 17 meters (18.068–18.168 MHz), and 12 meters (24.89–24.99 MHz). They were named after the World Administrative Radio Conference, which in 1979 created a worldwide allocation of these bands for amateur use. The bands were opened for use in the early 1980s. Due to their relatively small bandwidth of 100 kHz or less, there is a gentlemen's agreement that the WARC bands may not be used for general contesting. This agreement has been codified in official recommendations, such as the IARU Region 1 HF Manager's Handbook, which states: "Contest activity shall not take place on the 5, 10, 18 and 24 MHz bands."

In the United States, the Citizens Band Radio Service (CBRS), commonly called citizens band radio, is one of several personal radio services defined under Title 47 of the Code of Federal Regulations, Part 95. It is intended to be a two-way voice communication service for use in personal and business activities of the general public, and has a reliable communications range of several miles, though the range is highly dependent on type of radio, antenna and propagation.

<span class="mw-page-title-main">Personal radio service</span> Group of radio services

A personal radio service is any system that allows individual to operate radio transmitters and receivers for personal purposes with minimal or no special license or individual authorization. Personal radio services exist around the world and typically use light-weight walkie talkie portable radios. The power output, antenna size, and technical characteristics of the equipment are set by regulations in each country. Many regions have standardized personal radio service rules to allow travelers from one country to use their equipment in another country. Examples of standardized services include PMR446 and FM Citizens Band Radio (CB) in the EU and several other countries/regions. 26–27 MHz CB radio is the oldest personal radio service and is used in nearly every country worldwide, with many countries and regions copying the United States 40-channel frequency plan. In many countries, CB radio is less popular due to the availability of other personal radio services that offer shorter antennas and better protection from noise and interference.

The 8 meter band (40 MHz) is at present the lowest portion of the very high frequency (VHF) radio spectrum allocated to amateur radio use. The term refers to the average signal wavelength of 8 meters.

References

  1. ↑ "Short wave broadcast bands". MonitoringTimes.com. Retrieved 2010-11-19.
  2. ↑ Introduction on digital technology in the HFBC bands Accessed 2011-10-20. (Archived by WebCite at https://www.webcitation.org/62aCbliW6?url=http://www.itu.int/ITU-R/terrestrial/broadcast/hf/wrc-03/index.html Archived 2008-04-15 at the Wayback Machine
  3. ↑ http://stakeholders.ofcom.org.uk/binaries/consultations/cads_scheme/statement/statement.pdf [ bare URL PDF ]
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