Shortwave bands

Shortwave bands

Shortwave bands are frequency allocations for use within the high frequency radio spectrum. They are the primary medium for applications such as marine communication, 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 as measured by meters. Many bands, most notably the VHF 6 meters band, are notable for their behavior that depends on the season and the level of solar activity.

The "11-meter" (27 MHz) band is the most significant location allocated by most countries for Citizens' Band service (as well as some early cordless phones), though due to the band's propagation characteristics, which allow long-distance interference with local signals, most land mobile radio activity has moved to VHF or UHF, and most cordless phone activity is also in UHF or higher.

International broadcasting bands

The band frequencies below are derived from multiple sources, and different radios can have different numbers. Most international broadcasters use amplitude modulation with a stepping of 5 kHz between channels; a few use single sideband modulation. Different radios may define the bands differently.

*11 meters – 25.67–26.10 MHz – Very little broadcasting activity in this band. Day reception tends to be poor, night reception nonexistent. This band could be used for daytime 'single hop' regional coverage, but very few broadcast transmitters and antennas function in this band. Digital Radio Mondiale has proposed that this band be used for local digital shortwave broadcasts and conducted an extensive test of the concept in Mexico City in 2005. [] Not to be confused with the Citizens' Band 11-meter allocation, which in most countries runs from 26.965 MHz to 27.405 MHz.
*13 meters – 21.45–21.85 MHz – Somewhat shaky day reception, very little night. Similar case to 11 metres, but long distance daytime broadcasting keeps this band humming in the Asia-Pacific region.
*15 meters – 18.90–19.02 MHz – Seldom used.
*16 meters – 17.48–17.90 MHz – Day reception good, night reception varies seasonally, with summer being the best.
*19 meters –15.00–15.825 MHz – Day reception good, night reception variable, best during summer. Time stations such as WWV are clustered around 15 MHz.
*22 meters – 13.57–13.87 MHz – Similar to 19 meters; best in summer.
*25 meters – 11.50–12.16 MHz – Generally best during summer; said to be ideal during the period before and after sunset.
*31 meters – 9250–9995 kHz – Good year-round night band; seasonal during the day, with best reception in winter. Time stations are clustered around 10 MHz.
*41 meters – 7100–7600 kHz – Reception varies by region – reasonably good night reception, but few transmitters in this band are targeted to North America. According to the WRC-03 Decisions on HF broadcasting [] , in Region 1 and 3, the portion of 7100 to 7200 kHz will be turned to an amateur radio band and there will be new broadcasting portions – in all regions, 7350 to 7400 kHz newly allocated; in Region 1 and 3, 7400 to 7450 kHz allocated. This decision will be effective on March 29, 2009.
*49 meters – 5800–6300 kHz – Good year-round night band; daytime reception is lacking.
*60 meters – 4400–5100 kHz – Mostly used locally in tropical regions, though usable at night. Time stations are clustered around 5000 kHz.
*75 meters – 3900–4050 kHz – Mostly used in Eastern Hemisphere, not widely received in the Americas.
*90 meters – 3200–3400 kHz – Mostly used locally in tropical regions, with limited long-distance reception at night.
*120 meters – 2300–2495 kHz – Mostly used locally in tropical regions, with time stations clustered around 2500 kHz. Not technically a shortwave band; resides in the upper reaches of the medium wave band.

Amateur HF bands

Marine and land mobile allocations

The international maritime distress frequency is 2182 kHz; formerly 500 kHz was reserved for Morse Code distress signals, but this frequency allocation has been discarded in favor of systems such as GMDSS and Inmarsat. As mentioned above, most countries that have HF Citizens' Band allocations allocate 40 channels between 26.965 MHz to 27.405 MHz, in 10 kHz steps.

Military HF allocation

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 Western and Eastern 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 underuse of the HF bands.

The military in the Americas (as well as in 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 effect heating of bulk materials or adhesives for the purpose of drying or increasing the cure rate. The industrial use of the frequency was one of the motivations to permit widespread use by the citizenry of the 11 m band for CB Radio.

About a dozen narrow or "sliver" allocations for ISM exist throughout the radio spectrum.See ISM band for more information.

These allocations are perhaps the smallest in the HF band, with respect to national HF allocations.

ee also

*Shortwave and high frequency (HF)
*International broadcasting

External links

* [] -- A beginner's guide to shortwave radio.
* [ American Radio Relay League] -- the United States lobbying body for amateur radio and the body responsible for the ARRL Handbook
* [ Radio Amateurs of Canada] -- Canada's National Amateur Radio Society
* [ Passport to World Band Radio]
* [ World Radio and Television Handbook]
* [ SWDXER] ¨The SWDXER¨ - with general SWL information and radio antenna tips.
* [ EiBi & DX] - Complete list of International Broadcasting Stations worldwide, frequently updated.

Wikimedia Foundation. 2010.

Игры ⚽ Поможем написать реферат

Look at other dictionaries:

  • Shortwave — radio operates between the frequencies of 3,000 kHz (3.000 MHz) and 30,000 kHz (30.000 MHz) [ Tomislav Stimac, [ Definition of frequency bands (VLF, ELF... etc.)] . IK1QFK Home Page (] and came to be… …   Wikipedia

  • Shortwave radio — Shortwave can also refer to a shortwave trough meteorology. A solid state, analog shortwave receiver Shortwave radio refers to the upper MF (medium frequency) and all of the HF (high frequency) portion of the radio spectrum, between… …   Wikipedia

  • Shortwave listening — (abbreviated as SWLing) is the hobby of tuning for shortwave radio broadcasts located on shortwave frequencies, usually thought of as those from 1700 kHz (the upper limit of the AM broadcasting band) to 30 MHz (the lower limit of the tuning range …   Wikipedia

  • shortwave radio — a radio that transmits or receives shortwaves. * * * ▪ communications       transmission and reception of information by means of electromagnetic waves about 10 to 80 m (33 to 262 feet) in length having frequencies of approximately 29.7 to 3.5… …   Universalium

  • List of American shortwave broadcasters — Among the nations of the world, the USA is unique in that it has allowed private ownership of commercial and non commercial shortwave stations that are not relays of existing AM/MW or FM radio stations, as are common in Africa, Europe, Asia,… …   Wikipedia

  • WARC bands — The WARC bands are three portions of the shortwave radio spectrum used by licensed amateur radio operators. They consist of 30 meters (10.100–10.150 MHz), 17 meters (18.068–18.168 MHz) and 12 meters (24.890–24.990 MHz). [U.S. Amateur Frequency… …   Wikipedia

  • DXing — is the hobby of tuning in and identifying distant radio or television signals, or making two way radio contact with distant stations in amateur radio, citizens band radio or other two way radio communications. Many DXers also attempt to receive… …   Wikipedia

  • 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… …   Wikipedia

  • Radio broadcasting — Long wave radio broadcasting station, Motala, Sweden …   Wikipedia

  • Numbers station — Fictional example of a numbers station. Numbers stations (or number stations) are shortwave radio stations of uncertain origin. In the 1950s, Time magazine reported that the numbers stations first appeared shortly after World War II and were… …   Wikipedia

Share the article and excerpts

Direct link
Do a right-click on the link above
and select “Copy Link”