Frenzel

• Communication


  The process of exchanging information
• Key barriers to human communication


  • Distance
  • Language
• Electronic communications was discovered


  Nineteenth century
• Water is not a major communications medium
• Noise


  Random interference to transmitted signals
• Attenuation


  The communications medium causes the signal to be reduced in strength
• Another communications signal is not a source of noise
• Simplex


  One-way communications
• Full duplex


  Simultaneous two-way communications
• Baseband signal


  The original electrical information signal to be transmitted
• Modulation


  The process of modifying a high-frequency carrier with the information to be transmitted
• Multiplexing


  The process of transmitting two or more information signals simultaneously over the same channel
• Baseband


  Continuous voice or video signals
• Detection


  Recovering information from a carrier
• Facsimile


  Transmission of graphical information over the telephone network
• Telemetry


  Measuring physical conditions at some remote location and transmitting this data for analysis
• Radio astronomy


  Receiving electromagnetic emissions from stars
• Ham radio


  A personal communications hobby for individuals
• Radar


  Based upon reflected radio signals
• Wavelength


  27 MHz has a wavelength of approximately 11 m
• Radio signals


  Made up of electric and magnetic fields
• Voice frequency range


  300 to 3000 Hz
• Shortwaves


  Another name for signals in the HF range
• VHF


  The range in which television broadcasting occurs
• Infrared rays


  Electromagnetic waves produced primarily by heat
• Micron


  One-millionth of a meter
• Infrared frequency range


  0.7 to 100 um
• Wavelength of red light


  Approximately 7000 A
• 1. rays are not used for communications
• Bandwidth


  7 MHz for a signal occupying the spectrum space from 1.115 to 1.122 GHz
• FCC


  The agency that regulates and manages the electromagnetic spectrum in the United States
• EHF


  The frequency range that has more channel space available for signals compared to VHF and UHF
• Modulation


  Having an information signal change some characteristic of a carrier signal
• In AM, the carrier frequency remains constant
• Demodulation


  The opposite of modulation
• Modulator


  The circuit used to produce modulation
• Modulation index


  The ratio of the peak modulating signal voltage to the peak carrier voltage
• If the modulation index is greater than 1, the information signal is distorted
• For ideal AM, the modulation index is 1</b>
• Envelope


  The outline of the peaks of a carrier has the shape of the modulating signal