The Free Spectrums

As you probably know, any signal that is sent without wires is called a radio transmission. A common example is that the radio in your car receives transmissions. Similarly, a standard cell phone works by receiving—and transmitting—radio signals.

Every device that broadcasts a radio transmission does so at a particular frequency, which is the oscillations, or movement from peak to trough, of the electromagnetic wave created by the transmission.

The entire set of radio frequencies is known as the radio spectrum. Contiguous portions of the radio spectrum are called bands, as in “the FM band.”

Radio frequencies describe the oscillations of a radio wave. For example, if you are tuned to an FM radio station at 92.5, it means that ...

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