The 15-meter band (also called the 21-MHz band or 15 meters) is an
amateur radio
Amateur radio, also known as ham radio, is the use of the radio frequency spectrum for purposes of non-commercial exchange of messages, wireless experimentation, self-training, private recreation, radiosport, contesting, and emergency communic ...
frequency band spanning the
shortwave
Shortwave radio is radio transmission using shortwave (SW) radio frequencies. There is no official definition of the band, but the range always includes all of the high frequency band (HF), which extends from 3 to 30 MHz (100 to 10 me ...
spectrum from 21 to 21.45 MHz. The band is suitable for
amateur long-distance communications, and such use is permitted in nearly all countries.
Because 15-meter waves propagate primarily via reflection off of the
F-2 layer of the ionosphere, the band is most useful for intercontinental communication during daylight hours, especially in years close to
solar maxima
Solar maximum is the regular period of greatest solar activity during the Sun's 11-year solar cycle. During solar maximum, large numbers of sunspots appear, and the solar irradiance output grows by about 0.07%. On average, the solar cycle takes ...
, but the band permits long-distance without high-power station equipment outside such ideal windows. The 15-meter wavelength is
harmonic
A harmonic is a wave with a frequency that is a positive integer multiple of the ''fundamental frequency'', the frequency of the original periodic signal, such as a sinusoidal wave. The original signal is also called the ''1st harmonic'', the ...
ally related to that of the
40-meter band
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 7.000-7.100 MHz i ...
, so it is often possible to use an
antenna
Antenna ( antennas or antennae) may refer to:
Science and engineering
* Antenna (radio), also known as an aerial, a transducer designed to transmit or receive electromagnetic (e.g., TV or radio) waves
* Antennae Galaxies, the name of two collid ...
designed for 40 meters.
History
The 15-meter band was designated by the 1947 International Radio Conference of Atlantic City in part to compensate for the loss of the 160-meter band to amateurs by the introduction of
LORAN
LORAN, short for long range navigation, was a hyperbolic radio navigation system developed in the United States during World War II. It was similar to the UK's Gee system but operated at lower frequencies in order to provide an improved range u ...
during World War II. The 15-meter band opened to amateurs for CW operation only in the United States on May 1, 1952, and telephony operations were authorized above 21.25 MHz and Novice CW operations between 21.100 and 21.250 MHz on March 28, 1953.
Frequency allocation
United States
Key
Canada
Canada is part of region 2 and as such is subject to the IARU band plan.
Radio Amateurs of Canada
Radio Amateurs of Canada (RAC), known in French as Radio Amateurs du Canada, is the national association for Amateur Radio in Canada. It is a not-for-profit membership association with headquarters in Ottawa, Ontario, Canada, representing the in ...
offers the bandplan below as a recommendation for use by radio amateurs in that country but it does not have the force of law and should only be considered a suggestion or guideline.
[Canadian 0-30 MHz Band Plan http://wp.rac.ca/wp-content/uploads/files/pdf/RAC%20Bandplan%20December%201%202015.pdf accessed 1 December 2015]
Key
See also
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Shortwave bands
Shortwave bands are frequency allocations for use within the shortwave radio spectrum (the upper medium frequency Fband and all of the high frequency Fband). Radio waves in these frequency ranges can be used for very long distance (transcontinent ...
References
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* Click the 15 Meter button at the bottom of the page
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Amateur radio bands
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