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An Introduction To Satellite TV Technology

Television delivered by the means of communications satellite is called Satellite TV. A satellite dish and set-top receiver box is needed on Earth to receive the signal. Satellite TV offers a wide range of channels and services.

Satellite television begins with a transmitting antenna situated at an up-link facility. Very large satellite dishes, as much as 9 to 12 meters (30 to 40 feet) in diameter are used for uplink. The increased diameter leads to more precise aiming and improved signal strength at the satellite. The dish used for up-link is aimed at a specific satellite. The up-link signals are transmitted within a specific frequency range, so as to be received by one of the transponders tuned to that frequency range onboard the satellite. The transponder resends the signals back to Earth but in a different frequency band to avoid interference with the up-link signal. The resending typically happens in the C-band (4–8 GHz) or Ku-band (12–18 GHz) or sometimes both. The leg of the signal course from the satellite to the receiving Earth station is called the downlink.

The downlinked satellite signal becomes quite weak after traveling the great distance to Earth. The signal is collected by a parabolic receiving dish, which converges the weak signal to the dish’s focal point. A device called feedhorn is mounted on brackets at the dish's focal point. The signals at or near the focal point are collected by this feedhorn which is essentially the flared front-end of a portion of waveguide and then conducts them to a pickup connected to a low-noise block downconverter or LNB. The LNB amplifies the relatively weak signals and filters the chunk of frequencies in which the satellite TV signals are transmitted. The LNB then converts the block of frequencies to a lower frequency range in the L-band range. Direct broadcast satellite dishes are fitted with an LNBF which integrates the feedhorn with the LNB.

The satellite receiver set-top box then demodulates and translates the signals to the desired form of output for television, audio, data, etc. Sometimes, the receiver includes the capability to unscramble or decrypt; the receiver is then called an integrated receiver/decoder. 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 main advantage of satellite TV is that providers (like Dish Network or DirecTv) don’t have to lay miles upon miles of cable to deliver television programs to you. They don’t require broadcast centers in every city which duplicates equipment. This saves you money because satellite TV 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 TV has a less than 1% outage rate. Satellite TV companies rate significantly higher in customer satisfaction than cable television companies.