• Introduction
  • Specifications and Features
  • Working
  • Components
  • Benefits and Limitations
  • Conclusion

 

DTH stands for Direct-To-Home

The Direct-To-Home (DTH) service is a digital satellite service that provides television services direct to subscriber.

DTH does away with the need for the local cable operator and puts the broadcaster directly in touch with consumer.

The installation of a DTH Television consists of :

  • A Dish Antenna (60 to 90 cm) in diameter
  • A Conventional TV set
  • Set top box
  • Coaxial Cable between dish and set top box

  • The frequencies for DTH vary from region to region but it lies in Ku band of microwave .Uplink frequency range – 17.3 to 17.8 GHz Downlink frequency range – 12.2 to 12.7 GHz
  • An electronically controlled polarizer is used at receiving terminal for converting circularly received polarized signal to linearly polarized signal.
  • A DTH – TV satellite carries up to 32 high power Transponders.
  • Digital TV signals are transmitted as 20 Mbps QPSK signal occupying about 27 MHz of transponder bandwidth for a single channel.
  • MPEG-2 format is used for video compression.

Some of the features of DTH service are as following:

  • DTH offers better quality picture than Cable TV.
  • DTH can reach remote areas where terrestrial transmission and cable TV have failed to reach.
  • DTH also allows for interactive TV services such as movie-on-demand, and e-mail.
  • In DTH, the payments will be made directly by the subscriber to the satellite company offering the service.

  • The programming source are simply the channels that provide programming for broadcast.
  • Satellite TV provider get programming from two major source: International Channels(such as HBO,ESPN & CNN)& various Local Channels(Sahara TV, Doordarshan ).
  • These channels usually have a distribution center that beams their programming to a geostationary satellite.

  • A satellite dish is just a special kind of antenna designed to focus on a specific broadcast source. The standard dish consists of a parabolic (bowl-shaped) surface and a central feed horn. To transmit a signal, a controller sends it through the horn, and the dish focuses the signal into a relatively narrow beam.
  • The dish on the receiving end can’t transmit information; it can only receive it. The receiving dish works in the exact opposite way of the transmitter.
  • When a beam hits the curved dish, the parabola shape reflects the radio signal inward onto a particular point, just like a concave mirror focuses light onto a particular point.
  • The curved dish focuses incoming radio waves onto the feed horn.

  • The central element in the feed horn is low noise block-down converter.
  • Block-down convertor (so called because it converts a whole band or ‘block of frequencies’ to a lower band) i.e. it converts the 12.2 to 12.7 GHz band to 950 to 1450 MHz
  • An LNB sits on the end of an arm and faces the parabolic reflector(dish) which focuses the signals from a satellite into the feed horn of the LNB.

› The basic Set Top Box (STB) takes the signal from the satellite dish and converts it into a signal that can be used by a TV, sound amplifier, etc.

› STBs can act as a gateway between a television or PC and telephone, satellite, terrestrial or cable feed.

› The STB also accepts commands from the user and transmits these commands back to the network operator.

  • Cost effective communication, information and entertainment to all.
  • Small size terminal can provide up to 4000 channels and 2000 radio channels through a click of button and thus bring world’s information, news entertainment to your home.
  • DTH services bypasses mediators and thus content provider comes with customer directly.
  • DTH services are transparent providing digital quality video, audio, radio, and IP to all at equal prices and other benefits with reliability.

  • Under unfavourable climatic conditions the service remains unavailable.
  • The service is interrupted in case if the direction of dish is disturbed.
  • Transmission gets interrupted due to sun outage.

 

Satellite

  • Geostationary satellite plays an important role for DTH system.
  • They are positioned at an exact height of 36,000 km above earth.
  • They solve the problem of range and distortion by transmitting broadcast signals.

Polarization

  • It is a way to give a specific direction to a transmitted signal.
  • Signal transmitted by satellite can be polarized as linear(horizontal and vertical) or circular(left hand or right hand) .

Direct To Home Technology connects urban , rural and remote areas of the country and provide desire information, communication, education and entertainment at the click of button.