It’s important to note that satellite has been less successful in carrying local channels than the traditional cable system has. This shows some distinction between presenting local signals on a national satellite platform versus a local cable television system.
A normal cable tv provider simply collects over-the-air transmission signals from the surrounding area and broadcasts those signals to its subscribers. Therefore, a cable TV system usually retransmits ten to fifteen transmission signals at a time. DirecTV should retransmit more local channels from a single satellite constellation; the satellite works like the cable TV transmission office. Now-a-days, simultaneously, DirecTV retransmits the signals of more than 1000 local channels. This needs a massive quantity of capacity and this has been the most important engineering challenge DirecTV has faced over the past couple of years.
DirecTV came across this challenge by utilizing the spot-beam technology. First, DirecTV has launched spot-beam satellites that produced extra capability by reusing spectrum in various geographic areas. The CONUS-beam satellites have a single, multi-frequency footprint that focuses the complete area of the United States. At the same time as CONUS satellites are exceptional for retransmitting national programming, employing those satellites to retransmit local transmission programming is a very extravagant use of spectrum. Obviously, if one was trying to retransmit local channels in all markets all over the country through CONUS satellites, the capability on the satellites would rapidly be drained leaving petite, if any space for national cable programming. In contrast with the CONUS-beam satellites, spot-beam satellites are good enough for the retransmission of local transmission signals. This is possible, because, instead of looking the complete United States with a more number of transponders, the spot-beam satellites cover multiple, separate areas, each with only one or two transponders. Thus, the spot-beam satellites allow the geographic reuse of satellite frequencies. By looking separate and non-overlapping geographic areas, the spot-beams of the satellites can achieve much the same thing.
Secondly, the other technology employed to boost the capacity is compression, which is a technique for mathematically manipulating data to get rid of superfluous and unnecessary bits. During the early 1990s, the compression rates were approximately 5:1. However, now-a-days, for SD TV signals, the compression rates are normally between 11:1 and 12:1, and further developments are going on. DirecTV satellites possess a spot beam accompanying two transponders covering the area close to Washington, DC. By 12:1 compression, the retransmission of all the 12 analog broadcast stations of Washington in SD format can be achieved at the same time leaving extra capacity to carry the local signals in the other markets covered by the same spot beam. However, if DirecTV does not use compression for transmission, it would require a complete transponder to every station.
The capacity of a satellite operator to retransmit the local transmission signals in a specific market is not depends on how many transponders the satellite operator employs; however, it is important that how many transponders are obtainable in the spot beam covering that market. It is also essential that how much the satellite operator is proficient to compress the transmission signal at the same time maintaining the quality of the signal.