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Satellite TV Guide


Satellite TV

The broadcaster sends (transmits) the signal to a Satellite at certain  frequency (uplink frequency). The satellite then beams the signal back to earth at certain frequency (downlink frequency). This signal is collected and processed by a parabolic dish fitted with LNB. From LNB the signal goes to the Satellite receiver where it gets tuned into various channels. These channels can be viewed on TV through regular audio/video connections like RCA (composite) or S-Video.

A broadcast can be a TV, RADIO or DATA (used for internet applications) type.

A broadcast can be “Free-to-Air” or “Paid” one. The “Paid” type is usually encrypted/scrambled.

TV broadcast can be Analog or Digital. The Digital format has two sizes, SD (Standard Definition) and HD (High Definition).

Dish (parabola)

It is made up of aluminium-perforated sheets and frames. Usually comes in 6 or 8 pieces. These pieces have to be properly fitted to get the final parabolic shape. A 10 feet dish is enough for most uses. If the signal in you area is very week, then use a 12 feet dish. Signal strength will be week if trees or high-rise buildings are around.
Care during transportation/shifting: If you want to re-install the dish at a different location, carefully dismantle individual pieces and then re assemble without any skew. If you damage even a little, it will loose its parabolic shape and will not receive the signal properly.

Recent technological advancements reduced the size of dish to even 4 feet with non perforated solid aluminium sheet.

LNB

Low Noise Block converts a whole band or "block" of frequencies to a lower frequency and sends them out to the cable connector, which you connect to your satellite receiver via coaxial cable.
It is fitted at the center of the dish. This is the first part to fail when lightening strikes. Hence never forget to fix the plastic protective cover onto it.

Polariser

The old mechanical type polariser is fixed on top of LNB. The function of the polariser is to change the polarity from “Vertical” to “Horizontal”. The usefulness of polarity is that two different channels can be broadcast at the same frequency with one as V and the other as H. Also if two frequencies are very close, using different polarity will eliminate interference.
Nowadays the mechanical polariser is no more used. Instead, an electronic polariser is already inbuilt in LNB and this is more reliable.

Satellite Receiver

The old analog receiver is no more used because all broadcasts are made in Digital form. But standard digital receivers can only receive free-to-air channel (TV & RADIO). If you want to receive “Paid” channels, a special receiver is available with a card slot. The credit card sized pay channels card is provided by your local operator with channels and validity period information are fed into it. After inserting the card into the slot of your receiver, you can watch the paid channels. The validity period is usually 1 year and you have to renew it again (after paying!).

Tuning, programming and arranging all channels are done through the receiver. Do not keep it ON all the time. It can be switched off during nighttime. Never switch OFF the power whenever the receiver shows a message as “Saving data”. This message will be displayed when you change channel’s parameters, delete or add a channel or bring it to standby mode by pressing “POWER” switch of your remote control. At this moment when you switch off the power, the entire channel setting will get corrupted and your receiver will not show any channels next time you power ON. You have to set all the channels again from the beginning. 

For tuning a Digital channel we need three parameters.

1) Frequency GHz: The frequency the satellite uses to beam the transmission down to Earth. This is known as the "downlink" frequency

2) Symbol rate: The symbol rate is the speed at which the data on the transponder is transmitted, in thousands of symbols per second (ksym/sec or kBaud/sec).

3) Polarity: Vertical or Horizontal

Keep the receiver in search mode, enter frequency, symbol rate and polarity. Then keep moving the positioner until signal is detected. At this point press OK from the receiver’s remote control. All the channels at this frequency, symbol rate & polarity will be tuned automatically and comes under one TRANSPONDER. The other parameters like Audio PID, video PID etc will be set automatically.
If the positioner is not installed, then one person should move the dish slowly. Another person should watch the signal detection to fix a satellite position.

Video Format

Originally the Digital TV broadcasts used MPEG2 format, the video size in PAL mode is 720 X 576 pixels. The receivers were also designed to receive this.

Nowadays, MPEG4 format is being used widely. It has two types:
1) SD, the standard definition (720 x 576) pixels.
2) HD, the high definition ( 1920x1080) pixels.

To receive the MPEG4 content, a different receiver is required. The old MPEG2 receiver can not be used.

Video Band

There are two types of Bands available, the C Band and Ku Band. Only the C Band channels can be received normally. The Ku Band is used by DTH (Direct To Home) providers and they give a different dish and receiver.

Positioner

This is used of you want to see channels from multiple satellites. Each satellite beams the signal from different position. Hence the dish should be positioned to different angles in order to receive the signal. The positioner will physically move the dish with the help of a telescopic stepper motor/actuator. The satellite position is denoted as ° E (Degree East Longitude).

Example:
Satellite INSAT 2E/4A (83° E)
People living in Middle eastern countries should face the dish towards East, in India face the dish towards upwards and in South Eastern countries face the dish towards West. 

Usually one dish and positioner is used to cover 90° (from east or west to middle up facing sky). If you want coverage of 180°, then 2 sets are required each working at opposite sides. The telescopic actuator operation will be hard after few years of operation. Clean it and apply a small quantity of grease for smooth movement. If you continue to use without cleaning, the driver IC in you positioner will fail. After a heavy wind you may have to re-adjust your positioner a little.