A
radio band is a small
frequency band (a contiguous section of the range of the radio spectrum) in which
channels are usually used or set aside for the same purpose. To prevent interference and allow for efficient use of the radio spectrum, similar services are allocated in bands. For example, broadcasting, mobile radio, or navigation devices, will be allocated in non-overlapping ranges of frequencies.
Band plan For each radio band, the ITU has a
band plan (or
frequency plan) which dictates how it is to be used and shared, to avoid
interference and to set
protocol for the
compatibility of
transmitters and
receivers. Each frequency plan defines the frequency range to be included, how
channels are to be defined, and what will be carried on those channels. Typical definitions set forth in a frequency plan are: •
numbering scheme – which channel numbers or letters (if any) will be assigned •
center frequencies – how far apart the
carrier wave for each channel will be (see
channel spacing) •
bandwidth and/or
deviation – how wide each channel will be •
spectral mask – how extraneous
signals will be
attenuated by frequency •
modulation – what type will be used or are permissible • content – what types of information are allowed, such as
audio or
video,
analog or
digital •
licensing – what the procedure will be to obtain a
broadcast license ITU The actual authorized frequency bands are defined by the
ITU and the local regulating agencies like the US
Federal Communications Commission (FCC) and voluntary best practices help avoid interference. As a matter of convention, the ITU divides the radio spectrum into 12 bands, each beginning at a
wavelength which is a power of ten (10n) metres, with corresponding frequency of 3×108-
n hertz, and each covering a decade of frequency or wavelength. Each of these bands has a traditional name. For example, the term
high frequency (HF) designates the wavelength range from 100 to 10 metres, corresponding to a frequency range of 3 to 30 MHz. This is just a symbol and is not related to allocation; the ITU further divides each band into subbands allocated to different services. Above 300 GHz, the absorption of
electromagnetic radiation by
Earth's atmosphere is so great that the atmosphere is effectively opaque, until it becomes transparent again in the
near-infrared and
optical window frequency ranges. These
ITU radio bands are defined in the
ITU Radio Regulations. Article 2, provision No. 2.1 states that "the radio spectrum shall be subdivided into nine frequency bands, which shall be designated by progressive whole numbers in accordance with the following table". The table originated with a recommendation of the fourth
CCIR meeting, held in Bucharest in 1937, and was approved by the International Radio Conference held at Atlantic City, NJ in 1947. The idea to give each band a number, in which the number is the logarithm of the approximate geometric mean of the upper and lower band limits in Hz, originated with B. C. Fleming-Williams, who suggested it in a letter to the editor of
Wireless Engineer in 1942. For example, the approximate geometric mean of band 7 is 10 MHz, or 107 Hz. The band name "tremendously low frequency" (TLF) has been used for frequency and wavelength of 1–3 Hz | 300,000–100,000 km (1000 Mm), but the term has not been defined by the ITU.
IEEE radar bands Frequency bands in the
microwave range are designated by letters. This convention began around World War II with military designations for frequencies used in
radar, which was the first application of microwaves. There are several incompatible naming systems for microwave bands, and even within a given system the exact frequency range designated by a letter may vary somewhat between different application areas. One widely used standard is the
IEEE radar bands established by the US
Institute of Electrical and Electronics Engineers. ===EU,
NATO, US ECM frequency designations===
Waveguide frequency bands Comparison of radio band designation standards The frequency of 1–3 Hz == Applications ==