RTA 211 Lecture Notes - Lecture 8: Satellite Television, Amplitude Modulation, Circular Polarization
3 Apr 2018
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Document Summary
Programs transmitted over the air using radio frequency (rf) waves. Radiation of electromagnetic energy from an antenna to be transmitted. Travels at speed of light (300000 km/sec) When waves are received by receiving antenna, small electrical voltage is produced. Voltage is amplified and the info is retrieved and presented accordingly. Oscillator - produces electrical signal of a given frequency, controlled by quartz crystal. After amplification, voltage becomes radio frequency carrier. Speech and music used to modulate the carrier in standard radio broadcast transmissions. Varying the amplitude of the carrier can help with power. Am superimposes variations of original audio signal, peaks and valleys are dependent on volume of audio input. Other method of modulating the carrier is by varying the frequency. Louder the sound for modulation, greater change in frequency. Higher audio frequency makes the broadcast better quality compared to am. Wire or metal conductor used to radiate energy to transmit waves or pick up energy to receive waves.
