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Homework Help: Need help understanding how a radio works

  1. May 20, 2006 #1
    with the help of an oscillator you create a frequency but how exactly do you insert the electric signal you've gained from a microphone into that frequency?
    if i understood the microphone right it transfers the vibrations into electrical form by altering lets say the current so that different ammount of electrons pass trough the wire. then how do that altered current enter the oscillator circuit?
  2. jcsd
  3. May 21, 2006 #2

    Tom Mattson

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    The microphone would have to be connected (electrically) to the either a preamplifier or an amplifier. So I guess the answer to the question of how the altered current enters the oscillator would be: "Through a wire". But that seems like too simple of an answer. Do you have a schematic of the system you have in mind?
  4. May 21, 2006 #3


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    The concept you're looking for is called "modulation." Modulation is the technique of allowing one signal to change characteristics of another. In the case of a radio, the low-frequency audio signal is used to change either the amplitude (AM) or frequency (FM) of the carrier, which is generated by the oscillator.

    Amplitude modulation can be done with nothing more than a transformer. Frequency modulation is commonly done with a voltage-controlled oscillator (VCO).

    - Warren
  5. May 22, 2006 #4
    thanks for the help all.
    here's the schematic of what i have in mind, would it work as a simplified schematic for a radio where the Gate current is the mic signal?

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    Last edited: May 22, 2006
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