Satellite TV, Simplified: How Does Satellite TV Work?
By Darrin Meyer
Satellite TV can be a viable alternative to cable for many consumers, as it delivers hundreds of digital and HD channels plus features and options that compare with and sometimes top those offered by cable providers. All you need is the proper equipment to receive programming, which can be a plus for those in rural areas. Still, there is a lot of technology involved from source to endpoint to bring that programming to the TV.
Satellite TV broadcasts, at their most basic, are similar to terrestrial broadcasts. They are sent out from a powerful antenna at the uplink station as radio waves which are (for digital transmissions) converted into streams of digital data. The data is compressed using specific digital file formats such as MPEG-2 to send the greatest amount of data within the allowed bandwidth. The waves travel only in a straight line, so broadcasters direct the transmissions toward satellites that have been launched into orbit, which redirect the signals toward the earth. Transmissions can occupy different frequency ranges, which are known as the C Band, Ku Band and Ka Band.
Communications satellites are considered geosynchronous or geostationary, which means they revolve around the earth in a specified orbit at the same speed as the earth itself, directly above the equator at a height of 22,300 miles (36,000 km). Those used for TV transmissions can either be a Medium Power Satellite (MPS), which transmit at 50 watts, or a Direct Broadcast Satellite (DBS), which can transmit at up to 10 times that power. The signal received by the satellite is known as the uplink, and the signal sent to the points of reception is the downlink.
The downlink signal is received by a satellite dish, which is essentially an antenna designed for a specific type of reception. C Band transmissions are received by the large dishes commonly seen in the early days of satellite TV, while Ku and Ka band signals are picked up by the smaller dishes that are more prevalent today. The signals are converted to a lower frequency by a connected device known as an LNC (Low Noise Converter) or LNB (Low Noise Block converter), which then amplifies the signal to send to the tuner of the satellite receiver. The tuner selects a specific channel from the data received and translates the signals into video and audio for display on the TV.
Satellite TV broadcasts fall into two main categories : DBS and free-to-air (FTA), which commonly transmit via MPS satellites. DBS broadcasts are used by commercial subscription providers like DirecTV and Dish Network; the transmissions are encrypted and can only be decoded by subscribers using equipment authorized to receive that company's transmissions. FTA broadcasts are unencrypted and can be received by any user within range of the satellite. FTA receivers and dishes often make use of a Digital Satellite Equipment Control (DISEqC) switch, which allows the dish to rotate to tune to multiple satellites for the different FTA channels they carry.
Darrin Meyer has been writing since 2009. In addition to being a frequent blogger, his articles appear on eHow, Answerbag and other Web sites. Meyer has a Bachelor of Arts in broadcast journalism from the University of Nebraska-Lincoln.