Modulating Signals

Discussion in 'Homework Help' started by Corey Esson, May 7, 2015.

  1. Corey Esson

    Thread Starter Member

    Feb 8, 2015
    30
    1
    Hi all, I'm having a tough time on a couple of modulating signal questions. I'll upload a pic of the question in general. I think the answer is C. Only because the way I think I understand it is the bandwidth got overloaded and now the side bands are taking over? Does this make sense? Thanks to all in advance for any helpful responses.
    Corey
    Screenshot_2015-05-07-19-38-01.png
     
  2. t_n_k

    AAC Fanatic!

    Mar 6, 2009
    5,448
    782
    I doubt the carrier disappears from the spectrum. I would google "effect of over modulation in AM radio transmission".
     
    Last edited: May 7, 2015
    Corey Esson likes this.
  3. JoeJester

    AAC Fanatic!

    Apr 26, 2005
    3,373
    1,157
    Corey,

    You can eliminate some answers to arrive at the correct one.

    This is almost 2.2 x Ec .... Look at that and evaluate it against all the answers,
     
    Corey Esson likes this.
  4. Corey Esson

    Thread Starter Member

    Feb 8, 2015
    30
    1
    tnk, thank you, I'll try this.

    Joe Jester, I was thinking about the math as well but the answers weren't asking in mathematical options. That's where I got totally lost because of no math answer options.

    I'm going to Google tnk's suggestion here in a bit and see if I can decipher it. I thought modulation would be fairly simple and would pick it up fast....I was wrong.

    Thanks to both!
    Corey
     
  5. Corey Esson

    Thread Starter Member

    Feb 8, 2015
    30
    1
    Oh man.....well I Googled and read a lot on effect of over mod in am.....
    Now I'm more confused. But I'm also leaning towards D as well after reading into it. I guess I'm just going to have to pick one and hope its right, once I find the right answer I'll research it more from there.

    Thanks to you and JoeJester!
     
  6. JoeJester

    AAC Fanatic!

    Apr 26, 2005
    3,373
    1,157
    When you demodulate the AM signal, the overmodulated signal does not look like the original signal.

    What the oscilloscope shows is a 10kHz sinewave overmodulating the carrier. if you just trace the envelope, you will not see a nice 10 kHz sinewave. Since we are overmodulating, there are spurious emissions that could be out of the authorized bandwidth.

    D is the best answer.

    Look at a 99 pct modulation ... you can clearly see the undistorted 10 kHz signal
     
    Last edited: May 8, 2015
    Corey Esson likes this.
  7. Corey Esson

    Thread Starter Member

    Feb 8, 2015
    30
    1
    Thank you very much Joe!!
    This has been a tough headache!

    Corey
     
Loading...