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Homework Help: Building a RC circuit to pick up radio waves

  1. Nov 21, 2013 #1
    1. The problem statement, all variables and given/known data

    2. Relevant equations

    w = 1 / sqrt(LC)

    3. The attempt at a solution

    hi there, I

    1. I decided to choose, 93.3 MHz so 93.3 x 10^6 Hz is my freq.
    2. I googled how a band pass filter diagram should look like and I found this,

    is the only way to create a low pass combined with a high pass filter is using 2 resistors and 2 capacitors only? is it possible to just have 1 inductor and 1 capacitor with alternating current in series?

    3. I am having trouble finding the value since there are 2 missing variables in and only 1 equation.. I am thinking I am allowed to make a value for L or C and then use algebra to find the other
    1. The problem statement, all variables and given/known data

    2. Relevant equations

    3. The attempt at a solution
  2. jcsd
  3. Nov 21, 2013 #2
    There are other designs for band-pass filters. But I do not think you are supposed to google them or invent them. You must have studied them in your course, so use the designs known to you.
  4. Nov 21, 2013 #3
    Yeah I missed the lecture on this topic so I had to refer to the internet but from what ive learned high pass frequency uses the combination of a resistor and capacitor and its purpose is to filter out the low frequency and a low pass frequency is just the opposite.
  5. Nov 21, 2013 #4
    I recommend that you still try to rely on the course material as much as you can. Talk to a fellow student who was there, they may have something to say and some lecture notes to borrow or to copy. You are very likely expected to design a circuit of the particular kind or kinds addressed at the lecture. Use the Internet as a supplement to that, not as a replacement.
  6. Nov 21, 2013 #5
    Yes I understand that and I will get caught up on the information I missed, but under my current situation I have to use my resources available to me as of right now. Which is just the internet and these forums. My classmate is busy so he can't help me at the moment and since this problem is the only thing I need to complete so I am just focusing my attention on what is in front of me. But yes in the long run I am sure that there will be more difficult circuits I will be facing, not to be rude or anything but for now I would just like to get feedback on what I've done so far.
  7. Nov 21, 2013 #6


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    Staff: Mentor

    If there is no buffer between the 2 stages (LPF, HPF), then they will interact. You need to write the 2 KCL equations using the complex impedances (Zcap values are complex, Zr values are real, obviously), and solve for V3/V1 as a function of frequency.
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