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Interference of radio signals

  1. Jul 22, 2017 #1
    1. The problem statement, all variables and given/known data
    July 22,2017. The problem statement, all variables and given/known data Television and radio waves can reflect from nearby mountains or from airplanes. Such relfections can interfere with the direct signal from the station. a. Determine what kind of interference will occur when 75-MHz television signals arrive at a receiver directly from a distant station and are also reflected from an airplane 134 m directly above the receiver. (Assume a wavelength/2 change in phase of the wave upon reflection.) Explain your reasoning. b. Determine what kind of interference will occur if the plane is 42 m closer to the receiver. Explain your reasoning.
    2. Relevant equations
    v=f*wavelength v=3.00 X 10^8 m/s

    3. The attempt at a solution
    The attempt at a solution I found the wavelength, which is 4 m. I don't know what to do next. Can someone help me please? I don't know how you would know if it is in phase or not
     
  2. jcsd
  3. Jul 22, 2017 #2

    berkeman

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    Staff: Mentor

    Welcome to the PF. :smile:

    Draw a diagram of each situation. Then label each path with the number of wavelengths along each path. Then include the information about the inversion of the reflected wave, and figure out if you have constructive or desructive interference at the receiver from the reflected signal.

    BTW, even if it looks like the distances in one of the situations would result in wave cancellation at the receiver, remember that the reflection off the aircraft will likely weaken that signal, since it spreads out from the reflecting object (in this case the round aircraft hull).

    Please show us your sketches and your work. Thank you.
     
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