Why is Modulation important in Broadcasting??

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

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  1. loosewire

    AAC Fanatic!

    Apr 25, 2008
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    All the tech stuff, draw a straight line,that zero every things that is
    below the line or above is a signal called modulation.F.m. and a.m. looks
    differrent on scope. So zero you get a straight line ,you see nothing,send a
    signal you will see modulation.
     
  2. RAH1379

    Well-Known Member

    Dec 13, 2005
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    modulation is the information impressed upon the carrier. without modulation all you would hear is silence or a quiet spot in the static on the dial.
     
  3. ethan007

    Member

    May 11, 2009
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    Hey buddy I'm sorry to say but it is really not possible.

    Note from moderator - A commercial link in your signature line has been removed.
     
    Last edited by a moderator: May 11, 2009
  4. DonQ

    Active Member

    May 6, 2009
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    Even at 40 wpm, morse code would equate to information at about 3-5 Hz. This would make a pretty narrow peak on a spectrum analyzer. So a narrow peak would not necessarily mean it's not modulated.

    Suppose you put old-style teletype on a carrier, instead of morse code? That would be about 110 Hz. Would that be considered modulation?

    If you had a micro-controller keying a transmitter at 9600 baud (like I first did with a Z80 in about 1980-something), is that modulation?

    I can't help but think CW is a misnomer. Digital, 100% modulation at less than audio frequencies is still modulation. Lots of things don't exactly mean what they are named.
     
  5. leftyretro

    Active Member

    Nov 25, 2008
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    I agree. The problem is that the name CW, meaning continuous wave (or carrier), is not morse code, which has to turn the carrier on and off at a timed rate to send any useful information. So CW is a misnomer and assumes you understand that the carrier wave is going to be turned on and off to covey the message. In fact when the sender has no information to send he doesn't keep the key down to continue sending a carrier wave, he leaves the key up resulting in on carrier being transmitted. I would have called it KW (keyed wave) rather then CW.

    Lefty
     
  6. etuzuner

    Member

    Mar 21, 2009
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    I just want to add a different reason. As you know we have baseband and passband signals. These signal have differerent properties. I think you should take a look to these topics. (I wish I could write a whole definition but it takes so much time..)
     
  7. MKCheruvu

    Member

    Nov 20, 2012
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    The Antenna size and Power required for signal to travel long distance is inversly proportional to the Frequency of operation ie if the signal is of high frequency it can travel long distance with reasonably small size Antenna/power.However our message(Voice) happens to be of low Frequency.
    Hence a low frequency signal is mixed with a High Frequency signal and then carried to Longer distances efficiently.
    This process of low frequency signal (message) being mixed with Carrier (high frequency) signal is called Modulation.The different methods of combining are like AM,FM etc.
     
  8. KL7AJ

    AAC Fanatic!

    Nov 4, 2008
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    I can still copy 45 words a minute. :)

    Eric the Old
     
  9. davebee

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    Oct 22, 2008
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    I only just barely passed my 13 WPM CW test for my advanced license, and I think the only reason the old guys passed me was they were happy that a younger guy was at least trying to learn Morse.

    KM6VI
     
  10. YokoTsuno

    Member

    Jan 1, 2013
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    Yes you can. You have two problems though.

    - Because audio frequencies are low (20 – 20kHz) you need a huge antenna for effective reception. Hum picked up by audio systems is in fact broadcasting of the 50/60 Hz power grid.

    - You can't separate channels anymore once broadcast because they're all in the same frequency band. Direct broadcasting without carrier has the same effect as listening to a room full of people talking to each other. The only thing you hear is an unintelligable kind of buzzing. You can however overcome this via baseband coding, a technique used in CDMA cell phones, underwater acoustic modems, and data transmission over public address speakers.

    Correct, otherwise there wouldn't be any information contained in the carrier and yes it is a misnomer. In fact in modern terminology the name is amplitude-shift-keying (ASK) with 2 amplitude levels. ASK is also used in 8VSB modulation (used in ATSC). The difference is that 8VSB uses 8 amplitude levels instead of 2 and only part of one sideband.
     
  11. Wendy

    Moderator

    Mar 24, 2008
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    Congratulations, you have practiced the arcane art of necromancy, the revival of a long dead thread. Likely the OP (Original Poster) has solved his problem in the years that has passed, or thrown it away, or something.

    I think we are done here, if you want to continue this please start another thread, as the original thread belongs to the OP.
     
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