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Radio signal

  1. Nov 10, 2003 #1


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    it has always seemed incredible to me how little power it
    takes to transmit radio signals over vast distances,i have
    read about how these signals are self sustaining, i was
    wondering how long a signal could retain its information,
    could it go clear across the galaxy?
  2. jcsd
  3. Nov 10, 2003 #2


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    Well, if you could produce a laser beam with zero dispersion, you could, in fact, transmit a signal to Andromeda as easily as across your living room. However, real laser beams always have some divergence, and the power spreads out over a non-zero solid angle. As the receiver gets further and further away, the beam spreads more and more. The receiver in Andromeda won't get all the power of the signal unless he's using a HUGE detector!

    So it is, in fact, very difficult to transmit signals across cosmic distances.

    - Warren
  4. Nov 10, 2003 #3


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    thanks chroot,
    i think your answer has more significance than some would think
    its one for my personal think tank.
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