PrinComm Finals

• Communication is the process of sending and receiving messages between 2 or more points via electronic, electromagnetic waves.
• the objective of communication is to receive information correctly and clearly.
• • Information - is conveyed in bits and dits.
  • message - physical manifestation of information
• Hartley's Law states the information capacity of a noiseless channel.$C=$$2BWlog_2n=$$3.32(2BW)log_10n$
• Shannon-Hartley Theorem states the information capacity of a noisy channel.$C=$$2BWlog_2(1+S/N)=$$3.32BWlog_10(1+S/N)$
• • analog signal-physical quantity that varies with time
  • digital signal-ordered sequence of symbols
• • Simplex - one way communication
  • Duplex - two way communication
  • Half-duplex = transmission can occur in both directions but not at the same time.
  • full-duplex = transmission can occur in both direction and at the same time.
  • full-full duplex - possible to trasmit and receive but not between the same two location.
• Electronic communcation systems

  • it is the totality of the mechanism that provides the teansfer of information.
• Elements of a communication system (in order):

  1. Information Source
  2. Transmitter
  3. Transmission Channel; Noise, Interference, Distortion
  4. Receiver
  5. Destination
• Transmitter - used to convert an information into signal suitable for transmission over a given communication medium.
• Components of a Transmitter:

  1. Audio Amplifer - increase the level of audio signal
  2. Oscillator -generates carrier signal
  3. Modulation amplifier - amplifies the modulated signal for transmission
  4. Transmitting Antenna - radiates electromagnetic energy in space.
• Communication Channel - the medium by which the electronic signal is sent from one place to another.
• • Wire Medium - signal is confined within the proximity of the channel or medium.
  • Wireless Medium - signal is not subjected to limits, boundaries, or channel restrictions.
• • Noise - random undesirable electric energy that enters the communication system via the communication system via the communication medium and interferes with the transmitted message.
  • Distortion - waveform perturbation caused by imperfect response of the system
  • Interference - contamination by extraneous signals from human soruces.
• • EMI (Electromagnetic Interference) is any undesirable emission or any electrical or electronic disturbance, man made or natural, which causes an undesirable response, malfunctions or degradation in the performance of electrical equipment.
  • RFI (Radio Frequency Interference) is any undesirable electrical energy with content within the frequency range dedicated to radio frequency transmission.
• Attenuation - the reduction of signal amplitude as it passed over the transmission medium.
• Receiving Antenna - captures the electromagnetic energy.

  Demodulator - extracts the message from the carrier waves.
• Modulation - process of combining the carrier wave with the information signal. Process of altering the characteristics of the carrier signal.
• Bandwidth - EM spectrum occupied by a signal.
• • ELF (Extremely Low Frequency, 30 - 300 Hz)
  • VF (Voice Frequency, 300 - 3000 Hz)
  • VLF (Very Low Frequency, 3 - 30 KHz)
  • LF (Low Frequency, 30 - 300 KHz)
  • MF (Medium Frequency, 300 - 3 MHz)
  • HF (High Frequency, 3 - 30 MHz)
  • VHF (Very High Frequency, 30 - 300 MHz)
  • UHF (Ultra High Frequency, 300 - 3 GHz)
  • SHF (Super High Frequency, 3 - 30 GHz)
  • EHF (Extremely High Frequency, 30 - 300 GHz)
• Multiplexing - allows more than one signal to be transmitted concurrently over a single medium.
• Baseband Information can be sent directly and unmodified over the medium
• Carrier signal - a high frequency signal that is modulated by audio, video, or data.
• Radio Frequency (RF) Wave - electromagnetic signal that is able to travel long distance through space.
• AM - Amplitude Modulation

  FM - Frequency Modulation

  PM - Phase Modulation
• • Frequency - number of cycles of a wave
  • Wavelength - distance occupied by one cycle of a wave.
• Communications Act of 1934

  • act and its various amendments established regulations for the use of spectrum space.
• FCC - Federal Communications Commision

  Allocates spectrum space, issue licenses, set standards and police the airwaves.
• Gain - ratio of circuit's output to input
• • Joseph Henry transmitted the first practical electrical signal.
  • Samuel Finley Breese Morse invented the Telegraph.
  • Alexander Bain invented the facsimile.
  • Johann Philip Reis completed the first non working telephone
  • James Clerk Maxwell stated that light, electricity, and magnetism are all related.
  • Dr. Mahlon Loomis became the first person to communicate wirelessly through Earth's atmosphere
• Johann Philip Reis


  Completed the first non working telephone
• James Clerk Maxwell


  Stated that light, electricity, and magnetism are all related
• Dr. Mahlon Loomis


  Became the first person to communicate wirelessly through Earth's atmosphere
• Alexander Graham Bell and Thomas A. Watson


  Invented the telephone
• Thomas Alva Edison


  Invented the phonograph
• Heinrich Hertz


  Discovered EM waves and Radio Waves
• Marchese Guglielmo Marconi


  Builds his first radio equipment, a device that rings a bell from 30 ft. away
• Reginald A. Fessenden


  Transmits first human speech through radio waves and invented Amplitude Modulation
• Lee DeForest


  Invents the triode vacuum tube
• Major Edwin Armstrong


  Patents wide-band Frequency Modulation (FM)