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Radio Spectrum

Les Vedettes du Pont Neuf_Paris_France_052517
(Les Vedettes du Pont Neuf, Paris, France - Hsi-Pin Ma)


Electromagnetic Spectrum and Wave Communication


- Electromagnetic Spectrum

Electromagnetic energy travels in waves and spans a broad spectrum from very long radio waves to very short gamma rays. The human eye can only detect only a small portion of this spectrum called visible light. A radio detects a different portion of the spectrum, and an x-ray machine uses yet another portion. All together, electromagnetic waves make up what is called the electromagnetic spectrum. Radio waves are used for wireless transmission of sound messages, or for passing information.

Electromagnetic radiation travels in waves that "vibrate" at different frequencies. Radio waves are in the range of about 10 kHz (or ten thousand waves per second) to 100 GHz (which is one hundred million vibrations per second). Electromagnetic radiation is used for communications and transmission of information. The waves that are used in this way are radio waves, microwaves, infrared radiation and light. Radio waves - are used to transmit television and radio programs. Microwaves - are used to transmit satellite television and for mobile phones. Infrared - is used to transmit information from remote controls.


- Wave Communication

Today we use codes to send signals using electromagnetic radiation. There are two types of signal, analogue and digital. An analogue signal changes in frequency and amplitude all the time in a way that matches the changes in the voice or music being transmitted. A digital signal has just two values – which we can represent as 0 and 1. An analogue signal varies in frequency and amplitude. A digital signal has two values, 0 and 1 (or ‘on’ and ‘off’).

The signal (voice, music or data) is converted into a code using only the values 0 and 1. The signal becomes a stream of 0 and 1 values. These pulses are added to the electromagnetic wave and transmitted. The signal is received and then decoded to recover the original signal. Both analogue and digital signals can pick up unwanted signals that distort the original signal. These unwanted signals are called noise. Digital signals can be cleaned up in a process known as regeneration because each pulse must be a 0 or a 1, so other values can be removed. Analogue signals can be amplified, but the noise is amplified too. This is why digital signals give a better-quality reception. 
Digital signals give a better-quality reception because noise on digital signals is more easily removed.


Demand For Spectrum Is Exploding


Spectrum = electromagnetic energy. It is all around us. Radio spectrum is broken up into what we call frequency “bands” (distinct parts of spectrum based on how often their energy waves oscillate) to transmit and receive signals. A familiar example may be FM radio. That band, as the numbers on the dial will indicate, goes from 88 megahertz to 108 megahertz - a slice of this large range of spectrum is available for transmitting information.

How Does the FCC License Spectrum Use? To prevent chaos over the air. Spectrum is mostly licensed by both frequency bands and by geographic area. Generally, commercial licenses are awarded via competitive auction. Spectrum is a way to transmit and receive radio signals (like in your car). Some signals power mobile telephones and broadband. The FCC awards exclusive licenses to entities for much of the spectrum associated with the provision of radio, basic mobile phone, and advanced wireless services. Generally, in order to get mobile phone coverage, an entity that holds an exclusive license with the FCC for spectrum must be deploying service. Because the demand for spectrum has grown so quickly, particularly for mobile telecommunications, the FCC is reallocating spectrum historically available for broadcast TV stations to wireless telecommunications providers.



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