Complete guide to DTH setup

Direct-To-Home (DTH) uses some advanced technologies to deliver entertainment to your home directly. Learning about all these technologies is quite daunting. Consequently, most people dread it and happy to treat it as a black-box. However, thanks to advanced technologies and equipment, you don't have to be an expert in setting this up. Hope this guide will help you understand it better and fix small problems on your own rather than depend on call-center executives of your provider.

Also, Media reporters use DVB-S technology to stream LIVE feeds to media houses where the feed is recorded and packaged as a TV program. This means one can watch the Live event sans commercials using a STB if it's unencrypted!!

Signals, satellites and encryption

Initially, TV transmission was Analog. Hence ALL the TVs have built-in analog tuners. However, analog transmission has limited bandwidth which is not sufficient to transmit ever increasing number of channels. This paved the way for Digital Transmission which uses compression technology. As a side effect, this renders the TV built-in tuner useless. One needs a Set-Top Box (STB) to view digital transmission.

Edit (28/1/2016): Some countries have TVs which can decode digital content, but only FTA ones.

There are three ways to receive digital signals -

  • DVB-S/S2 for satellite reception (S2 supersedes S and is backward compatible)
  • DVB-T/T2 for terrestrial reception (T2 supersedes T and is backward compatible)
  • DVB-C/C2 for cable reception (C2 supersedes C and is backward compatible)


DTH is usually offered using DVB-S/S2. It is transmitted in Ku band (the other being C band) as it requires smaller antenna (60-90 cms) for reception. C band reception requires large antenna.

Listed below is the DTH providers in India along with the satellites and encryption being used. (Source: http://www.lyngsat.com/)

ProviderSatelliteEncryption
DD Free DishInsat 4BFree To Air (FTA)
Dish TVNSS 6Conax
Big TVJCSAT 4BNagaravision
Sun DirectMeasat 3Irdeto
AirtelSES 7Videoguard

Antenna

Brand

Any decent brand will do.

Positioning

There are three things related to positioning - Azimuth, elevation (and skew of LNB). Azimuth is measured from north, elevation can be fixed using compass on the dish and skew is measured with respect to vertical axis on LNB rotational plane.You can find these details for the choice of satellites from http://www.dishpointer.com. You don't have to bother about exact angles - an approximate positioning would do. In fact, in certain orientations, you can receive multiple satellite signals!!

If your choice of satellites is not covered in one orientation, you can either place multiple antennae or use a rotor. In both these configurations, your STB uses DiSEqC protocol to control what you're watching. If you place multiple antennae, you'd need a DiSEqC switch. If you plan to use a rotor, make sure it is DiSEqC compliant.

Low Noise Block (LNB) Down-converter

Brand

Any decent brand will do.

Type

An important factor to consider while buying LNB is - how many channels do you want to watch or record simultaneously. One can watch and record approximately 20 channels on a single tuned transponder. However, if the program you want to record is on a different transponder than the one you're watching, you'd need another tuner and a corresponding LNB output to feed it.

Set Top Box (STB)

An STB consists of following components:
  • Tuner
  • Common Interface (CI)
  • Conditional Access Module (CAM) along with Smart Card

Tuner

As in the case of LNB, the number of tuners required would depend on the number of channels do you want to watch or record simultaneously. Tuning to a particular transponder requires, at a bare minimum, three parameters - Frequency, Polarisation and Symbol Rate. e.g. it's usually mentioned as 11000 V 25000, where

  • 11000 is the frequency in MHz
  • V is Vertical Polarisation (H for Horizontal)
  • 25000 is the symbol rate in MSPS

Common Interface

Common Interface (CI) is required to use CAM. STBs without CI will only be able to receive FTA channels.

CAM

CAM along with Smart card are the ONLY pieces which are specific to the DTH provider. A list of CAMs is available at http://www.cardman.com/cams.html.



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