How Cable Television Works: The Tutorialby David Lipscomb
Cable television, introduced in the 1970s, offers a greater number of channels, while solving antenna reception problems. Using a direct feed to the television or decoder box, cable TV is the most widely used television reception medium. Understanding how cable television really works allows insight into how one cable leading into your home can carry so much information.
Cable channels are allowed bandwidth of 6 Megahertz, or MHz, per channel. Given that coaxial cable is capable of many times this, it can carry many channels into the home on a single RG-6 coaxial feed. Some cable providers use a thicker, stiffer cable, called RG-11, to get high-definition, or HD, cable service and broadband Internet into your home. This cable is capable of carrying delicate digital data for miles without loss.
How Companies Get Their Signals
It may be surprising to learn that most cable companies get their signals from, ironically, satellite providers. Using large dishes, these companies receive the channel data from their providers, package the channel and broadband Internet bundles as desired, and resell them to their subscribers. This makes sense if you reflect that no terrestrial broadcaster sends the types of channels you see on your local stations. On occasion, although rarely, cable television services can drop out due to severe weather, just like a satellite system you may have at home.
The magic of compression is that it allows cable television companies to send potentially thousands of channels to your home, each using the same 6-MHz bandwidth per channel. MPEG-2 and MPEG-4 are the two compression schemes found in cable TV broadcasts. MPEG stands for Motion Picture Experts Group. This technology aims to eliminate much of the unneeded data on the channel, while not adversely affecting picture quality. HD is enabled via cable, thanks to MPEG compression schemes. In fact, many channels are digitally encoded, and are unlocked by using a cable box. This encoding allows one cable to carry all channels, not requiring a second coaxial feed for premium channels.
Cable Redistribution Boxes
Cable companies use service redistribution boxes found in your neighborhood or yard to re-amplify the signals to you and your neighbors. Peering inside, you would see multiple coaxial cables connected to what appears to be a large splitter, which in turn is connected to a silver or black box. This allows the cable feed to be retransmitted for many miles without significant degradation. Fiber-optic cabling allows more data from the service provider, which then converts to coaxial cables leading into your home or business.