Dth – How It Works - Satellite & Cable TV
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1. 1 4 directly to a receiver unless you want to restrict viewing to just one of the four options Even if you do the receiver may not work It s not a good idea Use the Quad instead If you mix n match by picking a 90cm dish and a Universal LNB at random the chances are that the performance could be no better than that of a regular minidish As a general rule any standard LNB will work with a circular prime focus dish or an offset focus dish which is taller than it is wide which looks circular when viewed by the LNB However a dish which is wider than it is tall will need a special LNB Just to prove the point here is a typical Universal LNB used with a minidish The minidish is oval in shape being much wider than it is high Inside that plastic rain cover is the actual LNB Note the difference in scalar ring height red arrows The side projections allow the LNB to focus on a wide area in the horizontal plane while the top and bottom projections are longer and focus the LNB on a narrower area in the vertical plane This LNB is designed specifically for an oval dish and will give very poor results with a dish that is roughly circular or a dish that is taller than it is wide Here s another comparison The LNBF on the left has circular scalar rings inside the feedhorn It is designed to be used with a nearly circular dish The one on the right is designed specifically for a dish which is wider t2. just like a concave mirror focuses light onto a particular point The curved dish focuses incoming radio waves onto the feed horn In this case the point is the dish s feed horn which passes the signal onto the receiving equipment In an ideal setup there aren t any major obstacles between the satellite and the dish so the dish receives a clear signal In some systems the dish needs to pick up signals from two or more Satellites at the same time The satellites may be close enough together that a regular dish with a single horn can pick up signals from both This compromises quality somewhat because the dish isn t aimed directly at one or more of the satellites A new dish design uses two or more horns to pick up different satellite signals As the beams from different satellites hit the curved dish they reflect at different angles so that one beam hits one of the horns and another beam hits a different horn The central element in the feed horn is the low noise blockdown converter or LNB The LNB amplifies the signal bouncing off the dish and filters out the noise signals not carrying programming The LNB passes the amplified filtered signal to the satellite receiver inside the viewer s house THE RECEI VER The end component in the entire satellite TV system is the receiver The receiver has four essential jobs It de scrambles the encrypted signal In order to unlock the signal the receiver needs the proper decoder ch
3. 1500 3 4 11172 Horizontal BBC World Service Radio 21500 3 4 12535 Vertical Eurosport News 40700 2 3 12535 Vertical Fashion TV India 40700 2 3 12535 TCT Network 40700 Vertical 2 3 12535 Vertical India TV 40700 2 3 12535 Vertical Jaya TV 40700 2 3 12535 Vertical Asianet 40700 2 3 12535 40700 Vertical Sahara One 2 3 12535 Vertical Sahara Samay National 40700 2 3 Satellite amp Cable TV 12535 40700 Vertical Jeevan TV 2 3 12535 Vertical Jagran 40700 2 3 12535 Vertical ESPN India 40700 2 3 12535 40700 Vertical Kairali Channel 2 3 12535 Vertical CNN Headline News 40700 2 3 12535 Vertical CCTV 9 40700 2 3 12535 Vertical NDTV 24 X 7 40700 2 3 12535 40700 Vertical Headlines Today 2 3 12535 Vertical TV 5 Asia 40700 2 3 12535 Vertical MAA TV 40700 2 3 12535 Vertical Geo TV 40700 2 3 12535 40700 Vertical Dish TV Promotional Channel 2 3 12595 Vertical B4U Music 40700 2 3 12595 Vertical STC Music 40700 2 3 12595 Vertical Nepal 1 40700 2 3 12595 Vertical CNBC TV 18 40700 2 3 12595 Vertical CNN International Asia 40700 2 3 12595 Vertical Turner Classic Movies 40700 2 3 12595 40700 Vertical Balle Balle 2 3 12595 Vertical ETV Telugu 40700 2 3 12595 Vertical BBC World India 40700 2 3 12595 Vertical ETC Channel Punjabi 40700 2 3 12595 40700 Vertical Zee Cinema Asia 2 3 12595 Vertical ABC Asia Pacific 40700 2 3 12595 Vertical Trace TV 40700 2 3 12595 Vertical Aast
4. 4 12647 Vertical DD National 27500 3 4 12647 Vertical DD News 27500 3 4 12647 27500 Vertical DD Sports 3 4 12647 Vertical SS India 27500 3 4 12647 Vertical DD Bharati 27500 3 4 12647 27500 Vertical DD bangla 3 4 12647 Vertical DD Chandana 27500 3 4 12647 Vertical DD Gujarati 27500 3 4 12647 Vertical DD Kashmir 27500 3 4 Satellite amp Cable TV Vertical Vertical Vertical Vertical Vertical Vertical Vertical Vertical Vertical Vertical Vertical Vertical Vertical Vertical Vertical Vertical Vertical Vertical 21500 3 4 DD Malayalam DD Lok Sabha AIR Vividh Bharati 21500 3 4 21500 3 4 FM Rainbow Radio AIR Telugu AIR Marathi 21500 3 4 AIR Tamil 21500 3 4 21500 3 4 AIR Gujarati DD North East DD Oriya 21500 3 4 DD Podhigai 21500 3 4 21500 3 4 DD Punjab DD Sahyadri 21500 3 4 21500 3 4 DD Saptagiri Mh1 Music Jain TV Aakaash Bangla 21500 3 4 DD Rajya Sabha
5. 4 different dishes and the output marked OUT is connected to the receiver Again as n the 2 i X 1 the selection of the LNBs is done by choosing the appropriate Tone Burst A B C or D in the setup menu of the receiver E PAN Le DISH TV DTH Channel List Scrambled amp Pay Service Frequency Polarity Channels SR FEC 10977 ARY Digital India 10977 ETV Gujarati 10977 ETV Oriya 10977 ETV Bihar Satellite amp Cable TV 10977 Horizontal ETV UP 40700 213 10977 Horizontal ETV MP 40700 2 3 10977 Horizontal ETV Rajasthan 40700 2 3 10977 40700 Horizontal Zee Music 2 3 10977 Horizontal SS Music 40700 2 3 10977 Horizontal The Musik 40700 2 3 10977 Horizontal ARY One World 40700 2 3 10977 QTV 40700 Horizontal 2 3 10977 Horizontal ETV Bangla 40700 2 3 10977 Horizontal Euronews 40700 2 3 10977 Horizontal ETV Marathi 40700 2 3 10977 ETV Marathi 40700 Horizontal 2 3 10977 Horizontal ETV kannada 40700 2 3 10977 Horizontal ETV Urdu 40700 2 3 10977 ETV 2 40700 Horizontal 2 3 11172 Horizontal Smile TV 27500 3 4 11172 Horizontal Star Sports India 21500 3 4 11172 Horizontal MX 21500 3 4 11172 21500 Horizontal Action Cinema 3 4 11172 Horizontal Classic Cinema 27500 3 4 11172 Horizontal Premeire Cinema 27500 3 4 11172 Horizontal Pogo 27500 3 4 11172 NE TV 27500 Horizontal 3 4 11172 Horizontal Aaj Tak 21500 3 4 11172 Horizontal TCT Network 27500 3 4 11172 Horizontal SaB TV 2
6. Satellite amp Cable TV India s Largest Magazine Exclusively For CATY Industry 3 5 November 2004 JANUARY 2005 ae scatmag com SATELUTE SE SCaT INDIA 2004 News Columns Sat Update Industry Links Events Subscription Govt Policies Tech Articles DTH HOW IT WORKS Early satellite TV viewers were explorers of sorts They used their expensive S Band then C Band dishes to discover unigue programming that wasn t necessarily intended for mass audiences The dish and receiving eguipment gave viewers the tools to pick up foreign stations live feeds between different broadcast stations and a lot of other stuff transmitted using satellites Some satellite owners still seek out this sort of programming on their own but today most satellite TV customers in developed television markets get their programming through a direct broadcast satellite DBS provider such as DISH TV or the recently launched Doordarshan DTH platform The provider selects programs and broadcasts them to subscribers as a set package Basically the provider s goal is to bring dozens or even hundreds of channels to the customers television in a form that approximates the competition from Cable TV Unlike earlier programming the provider s broadcast is completely digital which means it has high picture and stereo sound guality Early satellite television was broadcast in C band radio in the 3 4 gigahertz GHz to 7 GHz frequency range Digital broa
7. average strength of all frequencies It will not tell you if some frequencies are missing An expensive meter looks at a specific frequency Sometimes more than one but it will not tell you if some frequencies are missing Also most meters rely on battery power If the battery can not supply enough current to the LNB it may give a false reading List of Universal LNB types Universal LNB 9 75 and 10 60 GHz L O Works in 2 bands 10 7 11 8 and 11 6 12 7 GHz 22 kHz signal switched Noise Figure usually 1 0 dB or better It has an Integral feed horn with 40mm neck available in some models A Universal LNB reguires a 22kHz signal at 0 5v p p to switch its Local Oscillator to 10 6GHz high band Otherwise it uses its 9 75GHz oscillator low band Polarisation switching is controlled by dc voltage supplied by the receiver 12 5v to 14 5v gives vertical and 15 5 to 18v gives horizontal polarisation A higher voltage than that may damage the LNB but most are OK up to 20v A voltage that is too low less than 12 5v will prevent the LNB from working correctly Most voltage settings are automaticall conrolled by the digital receiver when it selects Vertical of Horizontal modes CONECTI NG MORE THAN ONE SATELLITE RECEI VER TO A SINGLE DISH Twin output LNB Currently available in most shops dealing in satellite receiving equipment the twin output LNB provides two outputs to feed two separate receivers for independ
8. dcast satellite transmits programming in the Ku frequency range 10 GHz to 14 GHz There are five major components involved in a direct to home DTH satellite system the programming source the broadcast center the satellite the satellite dish and the receiver THE COMPONENTS Programming sources are simply the channels that provide programming for broadcast The provider the DTH platform doesn t create original programming itself it pays other companies HBO for example or ESPN or STAR TV or Sahara etc for the right to broadcast their content via satellite In this way the provider is kind of like a broker between the viewer and the actual programming sources Cable television networks also work on the same principle The broadcast center is the central hub of the system At the broadcast center or the Playout amp Uplink location the television provider receives signals from various programming sources compreses using digital compression if necessary scrambles it and beams a broadcast signal to the satellite being used by it The satellites receive the signals from the broadcast station and rebroadcast them to the ground The viewer s dish picks up the signal from the satellite or multiple satellites in the same part of the Sky and passes it on to the receiver in the viewer s house The receiver processes the signal and Satellite amp Cable TV passes it on to a standard television Lets look at each step in the
9. ent working Each output can be switched independently by 13 17 volt input by the individual receiver to change polarisation and by 22kHz to change the band Satellite amp Cable TV Dual LNB or Monobloc LNB This type of LNB has a single output and the actual satellite signal is selected by the receiver which sends a DisEgC 22kHz pulsed tone up the LNB cable So only one satellite transmission can be viewed at a time This is in contrast with dish systems that have two or more separate LNBs where with two receivers both satellite transmissions can be viewed or recorded simultaneously Quad output or Quad universal LNB This can feed four separate receivers Basicaly an LNB with four IF outputs Each receiver has independent control of polarisation and band via 13 17v switching and 22kHz o off respectively OCTO LNB As above but with eight independent outputs You can then connect upto eight satellite receivers to a single dish Quattro universal LNB This has four fixed outputs and is used only in head end I F distribution systems for apartment blocks One LNB supplies a head end unit that can provide typically up to 16 outputs for separate Digiboxes The four outputs of the LNB are as follows 1 Horizontal polarisation low band 2 Horizontal polarisation high band 3 Vertical polarisation low band 4 Vertical polarisation high band You should not connect any of the outputs
10. ha TV 40700 2 3 12595 40700 Vertical Sky Bangla 2 3 12595 Vertical NDTV India 40700 2 3 12595 Vertical Reality TV India 40700 2 3 12595 40700 Vertical Cartoon Network Asia 2 3 12595 Vertical Alpha Telugu 40700 2 3 12595 Vertical NTV Bangla 40700 2 3 12688 Vertical Zee TV Asia 27500 3 4 12688 27500 Vertical Zee News 3 4 12688 Vertical Alpha Marathi 27500 3 4 Satellite amp Cable TV 12688 Vertical Alpha Punjabi 21500 3 4 12688 Vertical Alpha Gujarati 21500 3 4 12688 Vertical Alpha Bangla 21500 3 4 12688 Vertical Trendz 21500 3 4 12688 Vertical Zee Movie Zone 21500 3 4 12688 Vertical Zee English 21500 3 4 12688 Vertical Zee Business 21500 3 4 DOORDARSHAN DD DIRECT DTH package Free Channels 12534 27500 Horizontal Kairali Channel 3 4 12534 Horizontal BBC World India 21500 3 4 12534 Horizontal ETC Channel Punjabi 21500 3 4 12534 Horizontal Smile TV 21500 3 4 12534 27500 Horizontal Aaj Tak 3 4 12534 Horizontal Zee Music 21500 3 4 12534 Horizontal Headlines Today 21500 3 4 12534 Horizontal Sun TV 21500 3 4 12534 Horizontal TV 9 21500 3 4 12534 Horizontal Star Utsav 21500 3 4 12534 Horizontal STV Marathi 21500 3 4 12534 FM Gold Radio 21500 Horizontal 3 4 12534 Horizontal AIR Kannada 21500 3 4 12534 Horizontal JAIR Bangla 21500 3 4 12534 Horizontal AIR Hindi 21500 3 4 12534 AIR North East 21500 Horizontal 3 4 12534 Horizontal AIR Punjabi 21500 3
11. han its height Satellite amp Cable TV Minidish upgrades Here is a Quad output LNB as supplied with a system with adaptors for the minidish The arrow points to the special oval shaped scalar steps in the feedhorn These cause the LNB to focus exactly on the oval shape of the dish using the full dish area but without picking up reflections from the wall behind Some dealers who are either unscrupulous or simple know no better are offering a standard Twin output or Quad output LNB with an adaptor to fit the minidish The adaptor fits very precisely however unfortunately the LNB will not give optimum performance resulting in rain drop out during bad weather Although the Quad output LNB kit may be available it is rather expensive If you must use the minidish and there are good aesthetic and environmental reasons to do so then you ll have to pay the price However you may prefer to buy a standard dish of say 90cm diameter and use a standard 40mm neck twin output or quad output LNB with this The match and fitting will be perfect and the rain drop out will be very rare The price of a 90cm dish with twin output LNB will be less than that of a Quad output LNB kit CAN CONNECT MORE THAN ONE TV TO A SINGLE SATELLITE RECEI VER The standard digital satelte receiver can tune in only one programme at a time and this programme can be routed around the house for viewing in other rooms To assist in this mo
12. ip for that programming package The provider can communicate with the chip via the satellite signal to make necessary adjustments to its decoding programs The provider may occasionally send signals that disrupt illegal de scramblers as an electronic counter measure ECM against illegal users It takes the digital MPEG 2 signal and converts it into an analog format that a standard television can recognize Since the receiver spits out only one channel at a time you can t tape one program and watch another You also can t watch two different programs on two TVs hooked up to the same receiver In order to do these things which are standard on conventional cable you need to buy an additional receiver Some receivers have a number of other features as well They pick up a programming schedule signal from the provider and present this information in an onscreen programming guide Many receivers have parental lock out options and some have built in Digital Video Recorders DVRs which let you pause live television or record it on a hard drive While digital broadcast satellite service is still lacking some of the basic features of conventional cable the ability to easily split signals between different TVs and VCRs for example its high quality picture varied programming selection and extended service areas make it a good alternative for some With the rise of digital cable which also has improved picture quality and extended channel selecti
13. mpression it can transmit about 30 channels At the broadcast center the high quality digital stream of video goes through an MPEG 2 encoder which converts the programming to MPEG 2 video of the correct size and format for the satellite receiver in your house ENCRYPTION amp TRANSMI SI ON After the video is compressed the provider needs to encrypt it in order to keep people from accessing it for free Encryption scrambles the digital data in such a way that it can only be decrypted converted back into usable data if the receiver has the correct decoding satellite receiver with decryption algorithm and security keys Once the signal is compressed and encrypted the broadcast center beams it directly to one of its satellites The satellite picks up the signal amplifies it and beams it back to Earth where viewers can pick it up THE DISH 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 Satellite amp Cable TV 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
14. on the TV war is really heating up Just about anything could happen in the next 10 years as all of these television providers battle it out WHAT IS AN LNB Satellite amp Cable TV Low Noise Block downconvertor so called because it converts a whole band or block of freguencies to a lower band An LNB sits on the end of an arm and faces the parabolic reflector dish which focusses the signals from a satellite into the feed horn of the LNB see pictures below The LNB converts the signals to a lower freguency and sends them out to the cable connector which you connect to your satellite receiver via coaxial cable HOW TO TEST AN LNB think my LNB is faulty How can test it The only way to fully test an LNB is to fit it to a suitable dish align the dish and LNB and connect a satellite receiver Then check to make sure every channel is there If no channels are missing and if it continues to work through a hot day and a cold night the LNB is fine However the reverse is not true If some channels appear to be missing this could be the fault of the cable the receiver or the dish distorted or misaligned It does not prove that the LNB is faulty So then you need to use a process of elimination by swapping the dish the cable and the receiver for a different make model as some receivers won t work correctly with some LNBs CAN T TEST IT WITH A METER A cheap satfinder meter simply looks at the
15. process in greater detail THE PROGRAMMI NG Satellite TV providers get programming from two major sources International turnaround channels such as HBO ESPN and CNN STAR TV SET B4U etc and various local channels SaBe TV Sahara TV Doordarshan etc Most of the turnaround channels also provide programming for cable television so sometimes some of the DTH platforms will ad in some special channels exclusive to itself to attract more subscriptions Turnaround channels usually have a distribution center that beams their programming to a geostationary satellite The broadcast center uses large satellite dishes to pick up these analog and digital signals from several sources THE BROADCAST CENTER The broadcast center converts all of this programming into a high guality uncompressed digital stream At this point the stream contains a vast guantity of data about 270 megabits per second Mbps for each channel In order to transmit the signal from there the broadcast center has to compress it Otherwise it would be too big for the satellite to handle The providers use the MPEG 2 compressed video format the same format used to store movies on DVDs With MPEG 2 compression the provider can reduce the 270 Mbps stream to about 3 or 10 Mbps depending on the type of programming This is the crucial step that has made DTH service a success With digital compression a typical satellite can transmit about 200 channels Without digital co
16. st satellite receivers have a RF Output RF Outlet socket For an additional sum you can buy a remote extender This plugs into the RF cable at the remote TV and can send handset signals back to the box A wireless remote extenders and extra remotes are also available from shops However yo should note that you can only tune into and watch any one programme at a time on all TV sets connected to a single receiver CAN CONNECT MORE THAN ONE DISH LNB TO A SINGLE RECEI VER 2X 1 DiSEqC SWITCHES This type os switch easly available in te market will enable you to connect two satellite dishes or two LNBs to a single satellite receiver The DiSEqC switch will enable the user to select one LNB signal between any 2 different LNBs of any type The 2 input ports marked SAT1 and SAT2 are connected to the 2 LNBs which may be on 2 different dishes and the output marked OUT Is connected to the receiver The selection of the LNBs is done by choosing the appropriate Tone Burst A or B in the LNB setup menu of the receiver Check the user manual of the digital rceiver for details DiSEgC 2 1 Switch 050 2150MMz babi C a A Si a a DMS International KRA DiSEqC 471 Switch Tora cp CE a Our oa 4 X 1 DiSEqC SWITCHES The DiSEqC switch will enable the user to select one LNB signal between 4 different LNBs of any type The 4 input ports marked SAT1 SAT2 SAT3 or SAT4 are connected to the 4 LNBs which may be on
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