electromagnetic wave

Discussion in 'General Electronics Chat' started by Lightfire, Apr 6, 2012.

  1. Lightfire

    Thread Starter Well-Known Member

    Oct 5, 2010
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    ok voice is transmitted thorugh em wave but how? does the em wave carry it? :
    and receiver gets the em wave and convert it to its original for m...
     
  2. vpoko

    Member

    Jan 5, 2012
    258
    47
    I'm not 100% sure I understand what you're asking, but I'll take a stab at it. When transmitting voice over EM waves, the voice is modulated over a carrier wave. For AM, you start with a sinusoidal carrier wave of some set frequency. Then you make changes to that carrier wave depending on the signal - in areas where there's more signal, the amplitude of the carrier wave is increased above where it would be had the signal not been modulated over it. For FM, the process is similar, except the signal impacts the frequency of the carrier wave instead of its amplitude.

    This picture shows an AM example: http://img.tfd.com/cde/_AMMOD.GIF
    While this pictures shows an FM example: http://img.tfd.com/cde/_FMMOD.GIF
     
  3. Wendy

    Moderator

    Mar 24, 2008
    20,766
    2,536
    The phrase you are looking for is modulation. There are many forms of modulation.

    When referring to radio frequency RF is the better choice of initials to em. Light is em, so are gamma rays, and lasers. The electromagnetic spectrum is vast, we use a small part of it.
     
  4. Lightfire

    Thread Starter Well-Known Member

    Oct 5, 2010
    690
    21
    meaning the sound is in modulation??????

    Sorry guys for my sentence..

    I really dont know how electromagnetic or RF wave extract the sound...

    so meaning,,, everys ingle modulation would result to different sound?? ah??
     
  5. bertus

    Administrator

    Apr 5, 2008
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  6. vpoko

    Member

    Jan 5, 2012
    258
    47
    Demodulating would recover the original signal, be it a sound or something else. If you ignore transmitting sound over radio waves (or any kind of EM waves since you could modulate light waves, etc) and just think of sound as pressure waves in a medium, it's the details (frequencies, amplitude, harmonics, phase, etc) of those pressure waves that determine the sounds you hear. Modulation "encodes" that already-existing signal onto another wave.
     
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