Radio - The History Of Radio, Radio And The Electromagnetic Spectrum, How Radio Signals Are Created, Modulation - Demodulation

Radio - The History Of Radio

In the nineteenth century, in Scotland, James Clerk Maxwell described the theoretical basis for radio transmissions with a set of four equations known ever since as Maxwell's Field Equations. Maxwell was the first scientist to use mechanical analogies and powerful mathematical modeling to create a successful description of the physical basis of the electromagnetic spectrum. His analysis pro…

Radio - Radio And The Electromagnetic Spectrum

Radio - How Radio Signals Are Created

Radio - Modulation

A radio signal by itself is like a mail truck without letters. A radio signal alone, without superimposed information, is called a carrier wave. An unmodulated radio signal conveys only the information that there was once a source for the signal picked up by the receiver. Adding information to a carrier signal is a process called modulation. To modulate a radio carrier means that it is changed in …

Radio - Wavelengths, Frequencies, And Antennas

Each radio signal has a characteristic wavelength just as is the case for a sound wave. The higher the frequency of the signal, the shorter will be the wavelength. Antennas for low-frequency radio signals are long. Antennas for higher frequencies are shorter, to match the length of the waves they will send or receive. It is a characteristic of all waves, not just radio signals, that there is great…

Radio - Radio Signals And Energy

Radio - Radio Signal Propagation

Radio signals with very short wavelengths generally follow straight line paths much as do beams of light, traveling from transmitter to receiver as a direct wave. Radio signals with very long wavelengths follow the curvature of the earth, staying close to the surface as signals called ground waves. Radio signals with intermediate wavelengths often reflect from layers of electrically-charged partic…

Radio - Shortwave Radio

Shortwave radio services may change frequency often as the ionosphere's reflectivity varies. Unlike domestic broadcast stations that stay on a single assigned frequency, shortwave broadcast stations move frequency to take advantage of hour-to-hour and season-to-season changes in the ionosphere. As the 11-year sunspot cycle waxes and wanes, shortwave stations the world around move to shorter…

Radio - Regulation Of Radio Transmissions

Radio - The Future Of Radio

Radio broadcasting now includes a newer, better digital system known as DAB, digital-audio broadcasting. Early tests indicate that a switch to digital imparts compact-disc quality to radio programming. There are two possible modes for DAB. In Europe, completely new stations on a different band of frequencies is favored. In the United States it seems probable that digital information will transmitt…