Shortwave bands

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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 Citizen's 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.

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[edit] 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. [1] Not to be confused with the Citizen's 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.
  • 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 mediumwave band.

[edit] Amateur HF bands

The following band allocations are the standard allocations used by the American Radio Relay League and the United States Federal Communications Commission. Consult your local regulatory body for further information; in particular, the 60-meter, 30-meter, and WARC (17 and 12 meter) bands may not be available in your home country.

  • 6 meters – 50–54 MHz – not actually a shortwave band but the lowest VHF band available to amateur operators, 6m is notable for its unusual propagation characteristics largely mediated by solar weather. Known as the "magic band", DXing on the band is largely done as a technical challenge. Listed here because it is commonly included on HF amateur sets.
  • 10 meters – 28–29.7 MHz – Best activity is during solar maximum; during periods of moderate solar activity the best activity is found at low latitudes. Also the site of frequent illegal unlicensed operation ("bootlegging") and freeband activity by operators using modified Citizen's Band equipment.
  • 12 meters – 24.89–24.99 MHz – Mostly useful during daytime, but opens up for DX activity at night during solar maximum. 12 meters is a WARC band.
  • 15 meters – 21–21.45 MHz – Most useful during solar maximum, and generally a daytime band.
  • 17 meters – 18.068–18.168 MHz – Similar to 20 m, but more sensitive to solar conditions. By unofficial agreement, this band is not used for amateur contesting, which makes it a fairly quiet place. It is often used for extended, informal chats known as "ragchews." 17 meters is a WARC band.
  • 20 meters – 14.0–14.35 MHz – Considered the most popular DX band; usually most popular during daytime. QRP operators recognize 14.060 MHz as their primary calling frequency in that band. Users of the PSK31 data mode tend to congregate around 14.071 MHz. Analog SSTV activity is centered around 14.230 MHz.
  • 30 meters – 10.1–10.15 MHz – a very narrow band, which is shared with non-amateur services. It is recommended that only Morse Code and data transmissions be used here, and in some countries amateur voice transmission is actually prohibited. Not released for amateur use in a small number of countries such as Oman and Thailand. Due to its location in the centre of the shortwave spectrum, provides significant opportunities for long-distance communication at all points of the solar cycle. 30 meters is a WARC band.
  • 40 meters – 7.0–7.3 MHz – Considered the most reliable all-season DX band, and most popular at night, and extremely useful for medium distance contacts during the day. Much of this band is shared with broadcasters, and in most countries only the bottom 100 kHz or 200 kHz are available to amateurs.
  • 60 meters – 5 MHz region – A relatively new allocation and only available in a small number of countries such as the United States, United Kingdom, Norway and Iceland. In most countries, the allocation is channelized, and in the USA it is mandatory to operate in upper sideband mode. Amateur equipment made in Japan or China often does not support this allocation, since it is not available in those countries.
  • 80 meters – 3500–4000 kHz – Best at night, with significant daytime signal absorption. Works best in winter due to atmospheric noise in summer. 80m phone operators have a reputation for rowdiness similar to CB operators. Only countries in the Americas and few others have access to all of this band, in other parts of the world amateurs are limited to the bottom 300 kHz or less. The subband from 3750–4000 kHz, which permits use of single-sideband voice, is often referred to 75 meters.
  • 160 meters – 1800–2000 kHz – Not a shortwave but a mediumwave band, and often taken up as a technical challenge in a manner similar to 6m. Most useful at night, though notoriously noisy. Also known as the "top band" and the "Gentlemen's Band", in apparent contrast to the supposedly freewheeling 80m allocation. Allocations in this band vary widely from country to country.

[edit] 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 Citizen's Band allocations allocate 40 channels between 26.965 MHz to 27.405 MHz, in 10 kHz steps.

[edit] 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 -- expect 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 civian fixed, maritime mobilie, and aeronautical mobile allocations on an ad-hoc (non-interference) basis.

[edit] Industrial/Scientific/Medical (ISM) HF allocations

Above 10mhz there are numerous frequences set aside for Radio Astronomy, Space Research (FCC terminology), and standard frequency and time services.

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

[edit] See also

[edit] External links

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