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Short Wave Transmission

Prasar Bharati has asked All India Radio to come up with a proposal to phase out Short Wave (SW) transmitters.

About SW:

  • Shortwave radio is radio transmission using shortwave radio frequencies, the range always includes all of the high frequency band (HF), and generally extends from 3-30 MHz (10 to 100 meters), above the medium frequency band (MF), to the end of the HF band.
  • Radio waves in the shortwave band can be reflected or refracted from a layer of electrically charged atoms in the atmosphere called the ionosphere.
  • Therefore, short waves directed at an angle into the sky can be reflected back to Earth at great distances, beyond the horizon.
  • This is called skywave or “skip” propagation, thus shortwave radio can be used for very long distance communication, in contrast to radio waves of higher frequency which travel in straight lines (line-of-sight propagation) and are limited by the visual horizon, about 64 km (40 miles).
  • Shortwave radio is used for broadcasting of voice and music to shortwave listeners over very large areas, sometimes entire continents or beyond.
  • It is also used for military over-the-horizon radar, diplomatic communication, and two-way international communication by amateur radio enthusiasts.

Advantages of Using Shortwave

Shortwave radio has a huge range – it can be received thousands of miles from the transmitter, and transmissions can cross oceans and mountain ranges. This makes it ideal for reaching nations without a radio network. SW transmissions are easy to receive, too: even cheap, simple radios are able to pick up a signal.

Other mode of Transmission

  • Medium-wave radio is generally used for local broadcasts and is perfect for rural communities. With a medium transmission range, it can reach isolated areas with a strong, reliable signal. Medium-wave transmissions can be broadcast through established radio networks – where these networks exist. 
  • Frequency Modulation (FM) provides a short-range signal – generally to anywhere within sight of the transmitter, with excellent sound quality. It can typically cover the area of a small city or large town – making it perfect for a radio station focusing on a limited geographical area speaking into local issues. While shortwave and medium-wave stations can be expensive to operate, a license for a community-based FM station is much cheaper.
  • Internet Radio: The rapid development of web-based technology offers huge opportunities for radio broadcasting. Internet-based stations are quick and easy to set up (sometimes taking as little as a week to get up and running and costs a lot less than regular transmissions. And because the internet has no borders, a web-based radio audience can have global reach.
February 2024