Product Code Database
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). in these frequency ranges can be used for very long distance (transcontinental) communication because they can reflect off layers of 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 cycle.
| Mostly used locally in tropical regions, with time stations at 2.5 MHz. Although this is regarded as shortwave radio, it is a medium frequency band. | ||
| 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. | ||
| 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. | ||
| Mostly used locally in Tropics, especially Brazil, although widely usable at night. Time stations use 5 MHz. | ||
| Good year-round night band; daytime (long distance) reception poor | ||
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,Introduction on digital technology in the HFBC bands
/a> 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. | ||
| 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. | ||
| Generally best during summer and Critical hours year-round | ||
| Substantially used in Eurasia. Similar to the 19 m band; best in summer. | ||
| Day reception good, night reception variable; best during summer. Time signal such as WWV use 15 MHz. | ||
| Day reception good; night reception varies seasonally, with summer best. | ||
| Lightly utilized; may become a Digital Radio Mondiale (DRM) band in future | ||
| 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. | ||
| Seldom used. Daytime reception is poor in the low solar cycle, but potentially excellent when the solar cycle (generally indicated by the Wolf number) is high. Nighttime reception nonexistent, except for local Surface wave 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 in bands allocated for Fixed wireless, with the 60-meter band extending as high as 5.13 MHz, the 49-meter band down to WRMI, the 41-meter band as high as WRMI and the 31-meter band extending as low as WINB.
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). 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 .
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