Why is Modulation important in Broadcasting??

Discussion in 'Wireless & RF Design' started by mabsj2, May 4, 2008.

Thread Status:
Not open for further replies.
  1. mabsj2

    Thread Starter Member

    Apr 24, 2008
    22
    0
    FM and AM are the two kinds of modulation used in Broadcasting.

    But i just don't get it, why is Modulation so important in Broadcasting.
    Can't a station be broadcast without doing any modulation??

    Why is it so important and is it done in Digital Broadcasting???
     
  2. Papabravo

    Expert

    Feb 24, 2006
    10,148
    1,791
    Because there can be no broadcasting without modulation, unless you belong to the vanishing breed of CW geeks.
     
  3. mabsj2

    Thread Starter Member

    Apr 24, 2008
    22
    0
    what's that??
     
  4. bertus

    Administrator

    Apr 5, 2008
    15,648
    2,347
  5. Wendy

    Moderator

    Mar 24, 2008
    20,766
    2,536
    Modulation is the voice and video info. No modulation, no radio, no audio.
     
  6. mabsj2

    Thread Starter Member

    Apr 24, 2008
    22
    0
  7. Caveman

    Active Member

    Apr 15, 2008
    471
    0
    What you are doing in a broadcast is transmitting information. What modulation is doing is putting that information at a specific frequency band. Different frequencies are used as different channels. If you just transmit the frequency (ie. no modulation), you only have one frequency worth of information, which is really nothing at all. You can't even make it bigger and smaller because that is amplitude modulation and adds bandwidth. It would be a single constant sine wave. That's it.

    BTW, CW, ie. continuous wave, is typically the method used for morse code where you either transmit or not the carrier frequency. But if you look at the math of it, turning on and off the carrier adds bandwidth (not much, but there is some), so it is a form of modulation as well. In fact it is a simplification of amplitude modulation.
     
  8. milkisgood

    New Member

    May 4, 2008
    6
    0
    The simple answer is that you MUST have modulated waves because normal voice/information is in a frequency range that is way too small to make it across any reasonable distance.

    So you have to combine those waves or "hide" those waves with something called a carrier signal (which is basically a much higher frequency signal) so that it will make it across any reasonable distance without much data loss or noise.

    That combination of information waves and carrier waves is called modulation and it's essential to have it to ensure that whatever a company broadcasts in one place is approximately reproduced in another (consumer) place.

    and that's the answer.

    (by the way, I'm describing FM here, but the same principle can be applied to AM)
     
  9. subtech

    Senior Member

    Nov 21, 2006
    123
    4
    I guess I'm part of the dying breed of Morse Code Geeks. (Geez! I'm dying? I guess if Papa says so........)
    Continuous Wave (A1A)
    Radio communication at its most basic (and some say its most fun) level.
    It takes effort.
    It takes "want to".
    Oh yeah, it also takes a radio.
    But, thats about all it takes.

    If you'd like to be part of a dying breed and have a ton of fun whilst you keel over, look here:
    http://www.fists.org/
     
    Last edited: May 4, 2008
  10. Papabravo

    Expert

    Feb 24, 2006
    10,148
    1,791
    CW (Continuous Wave) and Morse Code is about the only form of radio communication that does not rely on modulation. Unless you consider turning the transmitter on and off as a kind of modulation technique.
     
  11. beenthere

    Retired Moderator

    Apr 20, 2004
    15,815
    282
    Don't the gonzo speed bug types use two local oscillator freqs to modulate the carrier?
     
  12. Papabravo

    Expert

    Feb 24, 2006
    10,148
    1,791
    No. In fact that would almost defeat the purpose of having a narrow filter to improve the rejection of nearby signals. Paddles, like the Bencher BY-2, which I use are just two independent switches which go to a keyer circuit. It is the keyer circuit that produces precisely timed and spaced dits and dahs for the speed you select.
     
  13. AlexR

    Well-Known Member

    Jan 16, 2008
    735
    54
    Since turning a transmitter on and off produces sidebands it must be considered a form of modulation.
    Actually so-called CW is an example of AM with 100% modulation and a very low modulating frequency!!!
     
  14. mabsj2

    Thread Starter Member

    Apr 24, 2008
    22
    0
    Cotinues wave, morse code... sounds cofusing but i have learnt something atleast.
     
  15. thingmaker3

    Retired Moderator

    May 16, 2005
    5,072
    6
    If CW is considered modulation, it would be the oldest form of digital radio.:)
     
  16. Papabravo

    Expert

    Feb 24, 2006
    10,148
    1,791
    Many of us in the Amateur Radio Community consider it to be the original instant messaging. We were doing it long before the term was invented.
     
  17. Papabravo

    Expert

    Feb 24, 2006
    10,148
    1,791
    I don't see it that way, but there's room for all kinds. In fact what comes out the antenna looks like a pretty solitary peak on a spectrum analyzer.
     
    Last edited: May 5, 2008
  18. thingmaker3

    Retired Moderator

    May 16, 2005
    5,072
    6
    I recall an excerpt from some TV show where the world-record holder text-messager teenager-dude was out-performed in devastating style by two seasoned citizens using Morse code.
     
  19. Papabravo

    Expert

    Feb 24, 2006
    10,148
    1,791
    It was the Tonight Show with Jay Leno, and those guys were radio telegraphers and were clipping along at 40+ wpm.
     
    Last edited: May 7, 2008
  20. mabsj2

    Thread Starter Member

    Apr 24, 2008
    22
    0
    going to start doing Amateur Radio. i love radio.... that's why i am so curious about things concerning radio.
     
Loading...
Thread Status:
Not open for further replies.