(For example, the approximate geometric mean of Band 7 is 10 MHz, or 10 Designations for television and FM radio broadcast frequencies vary between countries, see Television channel frequencies and FM broadcast band.Since VHF and UHF frequencies are desirable for many uses in urban areas, in North America some parts of the former television broadcasting band have been reassigned to cellular phone and various land mobile communications systems.
In some cases, parts of the radio spectrum are sold or licensed to operators of private radio transmission services (for example, cellular telephone operators or broadcast television stations).
Ranges of allocated frequencies are often referred to by their provisioned use (for example, cellular spectrum or television spectrum).
High-frequency allocations are still designated for ships, although satellite systems have taken over some of the safety applications previously served by 500 k Hz and other frequencies.
2182 k Hz is a medium-wave frequency still used for marine emergency communication.
However, in recent years the largest use of these bands has been by short-range low-power communications systems, since users do not have to hold a radio operator's license.
Cordless telephones, wireless computer networks, Bluetooth devices, and garage door openers all use the ISM bands.
The radio spectrum is the part of the electromagnetic spectrum from 3 Hz to 3000 GHz (3 THz).
Electromagnetic waves in this frequency range, called radio waves, are extremely widely used in modern technology, particularly in telecommunication.
Airband refers to VHF frequencies 118 to 137 MHz, used for navigation and voice communication with aircraft.
Trans-oceanic aircraft also carry HF radio and satellite transceivers.
It is used for personal, small business and hobby purposes.