Airband or aircraft band is the name for a group of frequencies in the VHF radio spectrum allocated to radio communication in civil aviation, sometimes also referred to as VHF, or phonetically as "Victor". Different sections of the band are used for radionavigational aids and air traffic control. In most countries a license to operate airband equipment is required and the operator is tested on competency in procedures, language and the use of the phonetic alphabet. Spectrum usage The VHF airband uses the frequencies between 108 and 137 MHz. The lowest 10 MHz of the band, from 108 to 117.95 MHz, is split into 200 narrow-band channels of 50 kHz. These are reserved for navigational aids such as VOR beacons, and precision approach systems such as ILS localizers. , most countries divide the upper 19 MHz into 760 channels for amplitude modulation voice transmissions, on frequencies from 118 to 136.975 MHz, in steps of 25 kHz. In Europe, it is becoming common to further divide those channels into three (8.33 kHz channel spacing), potentially permitting 2,280 channels. Some channels between 123.100 and 135.950 are available in the US to other users such as government agencies, commercial company advisory, search and rescue, military aircraft, glider and ballooning air-to-ground, flight test and national aviation authority use. A typical transmission range of an aircraft flying at cruise altitude (), is about in good weather conditions. Other bands Aeronautical voice communication is also conducted in other frequency bands, including satellite voice on Inmarsat, Globalstar or Iridium, and high frequency voice. Usually these other frequency bands are only used in oceanic and remote areas, though they work over wider areas or even globally. Military aircraft also use a dedicated UHF-AM band from 225.0 to 399.95 MHz for air-to-air and air-to-ground, including air traffic control communication. This band has a designated emergency and guard channel of 243.0 MHz. Radio aeronautical navigation aids (navaids) use other frequencies. Non-directional beacons (NDB)s operate on low frequency and medium frequency bands 190–415 kHz and 510–535 kHz. The instrument landing system (ILS) glide path operates in the UHF range of 329.3–335.0 MHz with marker beacons at 75 MHz. Distance measuring equipment (DME) also uses UHF from 962 to 1150 MHz. Channel spacing Channel spacing for voice communication on the airband was originally 200 kHz until 1947, providing 70 channels from 118 to 132 MHz. Some radios of that time provided receive-only