Attributes of Radio Wave

In past decades messages were sent over the cables by alternately turning electrical currents on and off, producing a series of dots and dashes in accordance with a telegraph code. It was a significant advancement in communications with the development of radio, or wireless communication. Radio extended the communication range to ships at sea and to remote areas of the world, providing for the first time instantaneous and worldwide communications. Later on people learned how to encode and decode the human voice in a form that could be super imposed on electromagnetic waves and transmitted to a receiver; they used this mode as radio communication directly with human speech. Thus the human voice was transmitted thousands of miles, picked up by receivers and converted back into speech by loudspeakers. Radio was the first complete electronic communication system. Now we could transfer speech from one part of the earth to another or from a point on earth to a point in space. As well the message delivery rate was increased to the speed of light, making international communications possible within fractions of second, and space communications within seconds. The radiation concept of radio waves can be visualized by dropping a pebble into a pool of water. When the pebble enters the water, a surface disturbance is created, causing the water to move up and down. Of this point, the disturbance is transmitted on the surface of the pool in the form of expanding circles of waves. Hither the water is not moving away from the point. The type of wave produced is called the transverse wave. The wave occurring in a direction or directions are perpendicular to the direction of wave propagation. Identical are the characteristics of the radio waves. While there is no clear cut demarcation between radio waves and micro waves, electromagnetic waves ranging in frequencies between three kilohertz and one gigahertz are normally called radio waves. Nevertheless the behavior of waves, rather than the frequencies is a better criterion for classification. Following is the period of the radio waves. This period of a radio wave is the amount of time required for the completion of one full cycle of its frequency. As well the wavelength has to be considered. The space occupied by one full cycle of a radio wave at any given instant is known as wavelength. Whenever for example a radio wave could be frozen in place and measured, its wavelength would be the distance from any one point on a cycle to the corresponding point on the next cycle. Speed of a radio wave that is radiated into space by a transmitting antenna is simply that speed at which the wave travels. Radio waves travel in free space at about speed of light and the waves traveling inside earth's atmosphere have lesser speed due to barometric pressure, humidity, molecular content and so on.



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