Satellite TV programming is initially transmitted to orbiting communication satellites via broadcast stations which are located on earth. Broadcast stations receive their various national and local channels which are called turnaround channels (HBO, ESPN, CNN). They are then transmitted to the satellites, and the satellites transmit the compressed signals through powerful antennas back down to the client dishes on earth for the end users. The clients can receive the signals with small satellite dishes at their home or business.
The satellite signal, which is quite weak after traveling through space, is captured on earth by parabolic receiving dishes, which reflect the weak compressed signal to the focal point or center of the dish, is converted to a lower frequency, and then amplified by a low-noise block downconverter, or LNB. The amplified signal travels to the client’s receiver box through coaxial cable and it is converted to the L-Band frequency by an oscillator. Special electronics in the receiver are designed to convert the signal to a frequency that a standard television can use.
The communications satellites which are so critical to the distribution of broadcast signals are constantly in a state of geosynchronous orbit. This means that they revolve in the same direction as the earth, staying right above the same spot on the surface so that receiving dishes can operate in a fixed position. In order for the satellites to retain their orbit, there has to be a balance between the pull of the earth’s gravity and the centripetal force of the satellite’s orbit, which is pulling away from earth. This is possible by adjusting the altitude and orbiting velocity of the satellites. At 22,300 miles above earth, the satellites normally travel at approximately 7,000 miles per hour, not only to keep up with the earth’s rotation, but to balance the pull of gravity with centripetal force.