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.
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.
Each of these bands has a basic bandplan which dictates how it is to be used and shared, to avoid interference and to set protocol for the compatibility of transmitters and receivers.
As a matter of convention, bands are divided at wavelengths of 10n metres, or frequencies of 3×10n hertz. For example, 30 MHz or 10 m divides shortwave (lower and longer) from VHF (shorter and higher). These are the parts of the radio spectrum, and not its frequency allocation.
| Band name | Abbr | ITU band | Frequency and wavelength in air |
Example uses |
|---|---|---|---|---|
| < 3 Hz > 100,000 km |
Natural and man-made electromagnetic noise | |||
| Extremely low frequency | ELF | 1 | 3–30 Hz 100,000 km – 10,000 km |
Communication with submarines |
| Super low frequency | SLF | 2 | 30–300 Hz 10,000 km – 1000 km |
Communication with submarines |
| Ultra low frequency | ULF | 3 | 300–3000 Hz 1000 km – 100 km |
Submarine communication, Communication within mines |
| Very low frequency | VLF | 4 | 3–30 kHz 100 km – 10 km |
Navigation, time signals, submarine communication, wireless heart rate monitors, geophysics |
| Low frequency | LF | 5 | 30–300 kHz 10 km – 1 km |
Navigation, time signals, AM longwave broadcasting (Europe and parts of Asia), RFID, amateur radio |
| Medium frequency | MF | 6 | 300–3000 kHz 1 km – 100 m |
AM (medium-wave) broadcasts, amateur radio, avalanche beacons |
| High frequency | HF | 7 | 3–30 MHz 100 m – 10 m |
Shortwave broadcasts, citizens' band radio, amateur radio and over-the-horizon aviation communications, RFID, Over-the-horizon radar, Automatic link establishment (ALE) / Near Vertical Incidence Skywave (NVIS) radio communications, Marine and mobile radio telephony |
| Very high frequency | VHF | 8 | 30–300 MHz 10 m – 1 m |
FM, television broadcasts and line-of-sight ground-to-aircraft and aircraft-to-aircraft communications. Land Mobile and Maritime Mobile communications, amateur radio, weather radio |
| Ultra high frequency | UHF | 9 | 300–3000 MHz 1 m – 100 mm |
Television broadcasts, microwave ovens, microwave devices/communications, radio astronomy, mobile phones, wireless LAN, Bluetooth, ZigBee, GPS and two-way radios such as Land Mobile, FRS and GMRS radios, amateur radio |
| Super high frequency | SHF | 10 | 3–30 GHz 100 mm – 10 mm |
radio astronomy, microwave devices/communications, wireless LAN, most modern radars, communications satellites, satellite television broadcasting, DBS, amateur radio |
| Extremely high frequency | EHF | 11 | 30–300 GHz 10 mm – 1 mm |
radio astronomy, high-frequency microwave radio relay, microwave remote sensing, amateur radio, directed-energy weapon, millimeter wave scanner |
| Terahertz or Tremendously high frequency | THz or THF | 12 | 300–3,000 GHz 1 mm – 100 μm |
Terahertz imaging – a potential replacement for X-rays in some medical applications, ultrafast molecular dynamics, condensed-matter physics, terahertz time-domain spectroscopy, terahertz computing/communications, sub-mm remote sensing, amateur radio |
ITU
The ITU radio bands are designations 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[2]".The table originated with a recommendation of the IVth CCIR meeting, held in Bucharest in 1937, and was approved by the International Radio Conference held at Atlantic City 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.)[3]
| Band Number | Symbols | Frequency Range | Wavelength Range† |
|---|---|---|---|
| 4 | VLF | 3 to 30 kHz | 10 to 100 km |
| 5 | LF | 30 to 300 kHz | 1 to 10 km |
| 6 | MF | 300 to 3000 kHz | 100 to 1000 m |
| 7 | HF | 3 to 30 MHz | 10 to 100 m |
| 8 | VHF | 30 to 300 MHz | 1 to 10 m |
| 9 | UHF | 300 to 3000 MHz | 10 to 100 cm |
| 10 | SHF | 3 to 30 GHz | 1 to 10 cm |
| 11 | EHF | 30 to 300 GHz | 1 to 10 mm |
| 12 | 300 to 3000 GHz | 0.1 to 1 mm |
IEEE US
|
EU, NATO, US ECM frequency designations
|
Waveguide frequency bands
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By application
Broadcasting
Broadcast frequencies:- Longwave AM Radio = 148.5 – 283.5 kHz (LF)
- Mediumwave AM Radio = 530 kHz – 1710 kHz (MF)
- Shortwave AM Radio = 3 MHz – 30 MHz (HF)
The Apex band in the United States was a pre-WWII allocation for VHF audio broadcasting; it was made obsolete after the introduction of FM broadcasting.
