ABSTRACT
Programs from broadcast stations, multipoint distribution service (MDS), and direct broadcast satellites (DBS) are radiated from a transmitting antenna and sent to our receiver via radio energy. Radio waves result from oscillation. Unlike the rope waves and the sound waves, however, radio waves require no material medium for transmission. A radio transmitter produces radio waves by feeding an oscillating form of electric current into a transmitting antenna. In the transmitting antenna, the electric current creates coexistent electrical and magnetic fields of force around the antenna. Radio energy has a velocity of 300 million meters—186,000 miles—per second in a vacuum. Transmitters emit radio waves at a rate of thousands and millions per second, the exact rate varying according to service. Most current technologies require that an analog signal be sampled and encoded into digital form, then transmitted and decoded into analog form.
