The radio frequency spectrum is a natural and limited resource. Radio waves are a means of transferring information from one point to another without using any medium. One of the most important properties of any wave is its wavelength or frequency. Radio frequency determines the position in the radio frequency spectrum and therefore all the propagation properties and potential use of radio waves.

Because radio waves travel across country borders and can interfere with other radio waves, there are many rules, frequency plans, and procedures that define how to use the radio frequency spectrum to avoid interference. Because different frequencies have different properties, there are some general harmonized frequency bands that define the main purpose of the band and the basic technical parameters of transmitters using these frequencies. The so-called assignments are accepted internationally and provide basic rules for the use of frequencies. Then each allocation is further refined and countries may have special agreements on how to use specific frequencies.

One of the most popular services that use radio frequencies is terrestrial or satellite broadcasting. Radio and television are a well-known and established way of sending images and sound with radio waves. Because we typically want large coverage areas with few transmitters, we use high power transmitters at high transmission sites. Large coverage areas also mean coverage across the border.

This is very important information because in the same area there may be only one transmitter that can operate on a certain frequency without causing interference. Of course, there are special cases like digital transmission and single-frequency networks where nearby transmitters operate on the same frequency without causing interference, but careful frequency planning is a must for analog transmission.

For the broadcasting frequency bands there are many special regional agreements that define very precisely the particular frequencies assigned to each country, the procedures that will be used to modify the plan and also many rules that must be respected to avoid interference.

When we would like to listen to a particular radio, we need to know the frequency on which that radio broadcasts. A frequency is like a street address where each house has its own number. The same applies to television. However, for practical reasons, we generally do not deal with frequencies directly, but rather use channels where each channel number represents a (center) frequency with some channel bandwidth.

In general, most consumers are not aware of all the technical details that regulate the use of the frequency and are used to provide many wireless services. They only expect good music, quality movies and mobile phones that work anywhere.