A Dummies’ Guide to Satellite TV Technology
Satellite television is television transmitted by the means of communications satellite. A satellite dish and set-top receiver box is needed on ground to receive the signal. A large number of services and channels are offered by Satellite TV.
A transmitting antenna located at an up-link facility forms the foundation of satellite TV. Very large satellite dishes, as much as 9 to 12 meters (30 to 40 feet) in diameter are used for up-link. The large diameter results in more precise aiming and increased signal strength at the satellite. The dish used for up-link is pointed towards a specific satellite. The up-link signals are transmitted within a specialized frequency range, so as to be received by one of the transponders tuned to that frequency spectrum aboard the satellite. To avoid interference with the up-link signal, the transponder resends the signals back to Earth but in a different frequency band. The retransmission typically happens in the C-band (4–8 GHz) or Ku-band (12–18 GHz) or sometimes both. The leg of the signal path from the satellite to the receiving Earth station is called the downlink.
The downlinked satellite signal becomes quite feeble after traveling the long distance to Earth. A parabolic receiving dish collects the weak signal and reflects it to the dish’s focal point. Mounted on brackets at the dish's focal point is a device called a feedhorn. The signals at or near the focal point are collected by this feedhorn which is essentially the flared front-end of a section of waveguide and then sends them to a pickup connected to a low-noise block downconverter or LNB. The LNB boosts the relatively weak signals and filters the chunk of frequencies in which the satellite TV signals are transmitted. The LNB then transforms the block of frequencies to a lower frequency spectrum in the L-band spectrum. Direct broadcast satellite dishes are fitted with an LNBF which integrates the feedhorn with the LNB.
The signals are then demodulated and transformed to the desired form of output for television, audio, data, etc by the satellite receiver set-top box. The receiver is called an integrated receiver/decoder if the receiver includes the ability to unscramble or decrypt. The cable connecting the receiver to the LNBF or LNB must be of the low loss type RG-6, quad shield RG-6 or RG-11, etc. It cannot be standard RG-59.
The fact that satellite TV providers (like Dish Network or DirecTv) don’t have to lay miles upon miles of cable to deliver television programs to you is the main benefit of satellite TV. Equipment duplication is avoided since broadcast centers are not required in every city. This saves you money because satellite television is less expensive to maintain and up-grade, no re-laying of cable to up-grade services is needed. If the primary uplink center has a problem, the secondary uplink center automatically takes over broadcasting. That’s why satellite television has a less than 1% outage rate. Satellite television companies rate significantly higher in customer satisfaction than cable TV companies.