Radio Add

Sat, 13 November, 2010 9:16:42 PM
project
From: | Srimanta Sarkar <srimantasarkar@ymail.com>   View Contact |
To: | srimanta sarkar <srimantasarkar@ymail.com> | |
| | |
  | nitul project.docx (126KB) | |

Q. WHAT IS RADIO?1
Technically, radio is a small part of the electromagnetic spectrum (see Figure 1), so-called because electromagnetic waves are driven across space at the speed of light by electric and magnetic forces. Gamma rays, x-rays, ultra-violet, visible light and infra-red are also parts of the same spectrum. They all travel at the identical speed but have different properties and uses, depending on their frequency or wavelength 1.
If equipment generating radio frequency energy (a transmitter) is connected to an antenna (or aerial) the energy is radiated in the form of radio waves. Some of the radiated energy can then be collected by another antenna which, when coupled to a radio receiver, enables a link to be made between the transmitter and receiver. Adding information to the radio carrier wave enables messages to be transmitted. These messages may take the form of television programmes, voice messages, data or other forms of radio communication. Radio is an immensely versatile medium.
The way in which radio waves propagate or travel through the atmosphere varies with the frequency or wavelength of the radio signal. In general, the lower the frequency the further the distance that radio waves will travel. As the frequency increases, the waves may be obstructed or deflected by hills and buildings. At extremely high frequencies, rainfall and other weather conditions can significantly limit the effective operating range of radio communications. These propagation characteristics mean that different bands of frequencies are suited to particular types of radio use. For example, for national and international broadcasting the long-wave (approximately 148-283 kHz) and medium-wave (approximately 526-1606 kHz) bands are used. At the...