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Radio. *Warning* Heavy Science Content Ahead. Baghdad battery – 250 BCE. Electricity was a heavy duty toy for decades, including Ben Franklin and his kite, people rubbing cat skins on glass or amber rods, spinning sulfur balls, and sparking everything and everyone in sight.

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PowerPoint Slideshow about 'Radio' - Jeffrey


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Presentation Transcript
slide6
Electricity was a heavy duty toy for decades, including Ben Franklin and his kite, people rubbing cat skins on glass or amber rods, spinning sulfur balls, and sparking everything and everyone in sight
luigi galvani 1786
Luigi Galvani - 1786
  • Believed everything contained electricity
  • Looked for “animal magnetism”
  • Touched different metals to frogs’ legs which twitched
alessandro volta 17969
Alessandro Volta - 1796
  • Volta took Galvani’s experiment and showed that it was the current produced by the different metals that caused the twitch
  • Built a pile of alternating sandwiches of zinc and copper in an acid and created electicity
oersted s experiment 1820
Oersted’s experiment - 1820
  • In a lecture in Copenhagen he performed an experiment to demonstrate there was no connection between electricity and magnetism by showing that an electric current passing through a wire wouldn’t affect a nearby compass needle
slide12
Imagine his surprise when the needle swung the moment he turned on the current
  • He demonstrated that electricity created a magnetic field
william sturgeon 1825
William Sturgeon - 1825
  • Created the first electromagnet by wrapping wire around a soft iron bar and sending a current through the wire
  • Electricity can create magnetism
michael faraday 1826
Michael Faraday - 1826
  • Reversed Sturgeon’s experiment
  • Showed that magnetism could create an electric current
slide16
Used a an on-off switch – the telegraph key – to turn and electric current on and off, sending pulses of current through a wire to an electromagnet that would click in time to the pulses
slide20
Examined physical sensations
    • Can you feel colors
    • Can you hear shapes
    • Can you smell sounds
  • Discovered that each sense detects different things
  • We think this is obvious, but no one had proven it before. Remember “common sense”?
slide22
Meuller’s pupil
  • Investigated hearing
  • Noticed sound produced vibrations
slide24
Did the vibrations operate at different frequencies?
    • They did
    • Thus, sound traveled at different frequencies
  • Used an electromagnet to attract the arms of a tuning fork, causing it to vibrate and produce sound
leon scott de martinville phonautograph 1857
Leon Scott de Martinville - phonautograph - 1857
  • Attached a bristle to a membrane at the end of a cone, set the bristle to touch a piece of smoked glass
  • Spoke into the cone
  • membrane vibrated to the sound and the bristle etched a wavy line onto the smoked glass
the telephone 1876
The Telephone - 1876
  • Scott’s membrane, Faraday’s electromagnet, Oersted’s and Sturgeon’s electromagnet, Morse’s wire and electrical current, Heimholtz’s vibration, Scott’s membrane
slide31
Hemholtz’s pupil
  • Investigated whether electricity traveled in frequencies the way sound did
slide34
Demonstrated that electricity traveled through air at specific frequencies, just like it did through wires
tesla coil 1891
Tesla coil - 1891
  • Developed the first amplifier coil, the Tesla coil
  • Raised the voltage of an electrical current high enough to allow the air to conduct the current
  • Key to wireless transmission of radio waves
slide43
Felt that the variation in electrical amplitude created by a voice, just like on a telephone, could be carried by electrical wave of a radio signal
  • Did the first voice broadcast in 1900
    • Short range
    • Poor quality
  • Needed far more power
slide45
Developed the Alexanderson Alternator, a machine capable of generating the power, up to 100,000 hertz, that Fessenden needed to piggyback voice onto radio waves
  • In Dec. 1906, Fessenden did the first good voice and music broadcast, going hundreds of miles
    • Poetry and a Bible reading
    • A woman singing opera
    • A violin playing a Christmas carol
slide48
The audion tube is actually a Fleming valve (British term for tube) invented in England
  • de Forest simply added the bent wire
slide50
Audion tube amplified the radio signal the way the Alexanderson generator increased the electrical power
  • de Forest didn’t know how the audion worked
  • Another man did
slide52
Investigated the audion tube, figured out how it worked, and improved it
  • Developed “regeneration”
    • The signal was fed back into the tube over and over again, up to 20,000 times a second
    • Vastly increased the power of the tube to output the signal – it was an amplifier
    • Raise the level enough and the tube becomes a transmitter
    • Armstrong invented the ability to broadcast sound
slide53
It combined high frequency waves with low frequency waves, then fed them back into the system to amplify the signal and increase its sensitivity
  • Resulted in the creation of the home, and the portable, radio
armstrong s superheterodyne
Armstrong’s superheterodyne
  • Armstrong’s next invention was the superheterodyne
slide57
Enamored of radio
  • Saw the possibilities
  • Wrote the “Radio Music Box Memo” that outlined the commercial possibilities of radio
rca radio corporation of america
RCA (Radio Corporation of America)
  • After World War I
  • Four companies merged their patents to create RCA
    • American Marconi
    • General Electric
    • American Telephone & Telegraph
    • Westinghouse
  • Sarnoff named as commercial manager
slide59
Used Armstrong’s inventions, building superheterodyne radios to build RCA, the Radio Corporation of America, into one of the biggest companies in the world
radio stations soon opened all over the u s

Radio stations soon opened all over the U.S.

Including KWSC (now KWSU) in 1922, one of the first radio stations in the country

examples of programming
Operas

Concerts

Sports

News

Dramas

Comedies

Variety shows

Soap operas

Pretty much everything we get on TV today

Examples of programming
slide70
It was assumed that radio would be dead
    • Audiences would watch TV instead of listening to the radio
    • TV took over so many of the radio programs
      • Soap operas
      • Dramas
      • Sitcoms
      • Sports
      • news
new kinds of programming
New kinds of programming
  • Music
    • Top 40
    • Country
    • Rock
    • Easy listening
    • Golden oldies
  • Talk shows