Dismiss Notice
Join Physics Forums Today!
The friendliest, high quality science and math community on the planet! Everyone who loves science is here!

Homework Help: Designing a FM radio receiver

  1. Nov 14, 2007 #1
    1. The problem statement, all variables and given/known data
    Designing an FM Radio Receiver. You enjoy listening to KONG-FM, which broadcasts at 96.6 MHz. You detest listening to KRUD-FM which broadcasts at 96.5 MHz. You live the same distance from both stations and both transmitters are equally powerful, so both radio signals produce the same 1.0 V source voltage as measured at your house. Your goal is to design an L-C-R radio circuit with the following properties: i) It gives the maximum power response to the signal from KONG-FM; ii) the average power delivered to the resistor in response to KRUD-FM is 1.00% of the average power delivered to KONG-FM. This limits the power received from the unwanted station, making it inaudible. You are required to use an inductor with L = 1.00 ┬ÁH.

    a) Find the capacitance C that satisfies the design requirements?
    wrong check mark F
    (b) Find the resistance R that satisfies the design requirements?

    2. Relevant equations
    wL = 1/wC when at max. power and the angle phi = 0 degrees
    but i am having trouble with the 1% of the power part of the problem and how to involve that into this.
    96.6 MHz = 606955700.7 rad/sec
    96.5 MHz = 606327382.1 rad/sec
    L = 1.0e-6 H
    V = 1.0 V

    3. The attempt at a solution
    C =1/(w^2)L
    How do I involve the power into this?
    Pavg = 0.5*Imax*Vmax*cos(phi)
    Pavg = Irms*Vrms*cos(phi)
    Pavg = (Irms^2)*R
  2. jcsd
  3. Dec 4, 2007 #2
    This is a screenshot of the solution from a PDF that I found. I had a little bit of trouble with the same problem.

    This helped me figure it out.

    Came across this in google, I am probably too late though.

    Attached Files:

Share this great discussion with others via Reddit, Google+, Twitter, or Facebook