FSK (frequency shift keying) modulation and demodulation

Discussion in 'The Projects Forum' started by gogos, Dec 12, 2012.

  1. gogos

    Thread Starter New Member

    Sep 19, 2012
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    Hello,

    I need for FSK modulation scheme with a Hartley oscillator and varicap diode.
    Does anyone have such a scheme?

    Thanks!!! :)
     
  2. bertus

    Administrator

    Apr 5, 2008
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    Hello,

    Do you want the modulate the RF?
    At what frequencies should this oscillator work?
    Normaly the FSK is done in audio range and modulated on th RF.

    Bertus
     
  3. gogos

    Thread Starter New Member

    Sep 19, 2012
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    I need coherent binary FSK modem with Hartley oscillator, modulator and demodulator for my graduate work. I think that This oscillator should work to 1200Hz for "0" and 2200Hz for "1".

    :)
     
  4. bertus

    Administrator

    Apr 5, 2008
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  5. gogos

    Thread Starter New Member

    Sep 19, 2012
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    Thanks Bertus, but I need a elektric scheme of FSK modulation with Hartley oscillator and varactor diode.......:)
     
  6. bertus

    Administrator

    Apr 5, 2008
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    Hello,

    You will not manage the 1200 vs 2200 Hz using a varactor diode.
    The capacity change would be to large.

    Better make two oscillators and switch between them.

    Bertus
     
  7. gogos

    Thread Starter New Member

    Sep 19, 2012
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    Hm, Then I could use a nearer frequency.

    :)
     
  8. gogos

    Thread Starter New Member

    Sep 19, 2012
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    I think that the frequency range is not as important. It is important that to work at a high frequencies (>1kHz).
     
  9. gogos

    Thread Starter New Member

    Sep 19, 2012
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    Does anyone have such a scheme?
     
  10. gogos

    Thread Starter New Member

    Sep 19, 2012
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    There are a scheme of Hartley oscillator and Hartley oscillator with varicap diode. Frequency of "1" and "0" are almost identical (f1=2.212MHz, f0=2.201MHz). Does anyone know how to set the difference frequency is about 200-400kHz?


    Sorry for my bad English.
     
  11. bertus

    Administrator

    Apr 5, 2008
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    Hello,

    When you make C5 larger, the influence of the BB112 will be larger.
    Now you have a VERY small value for C5.

    Bertus
     
  12. gogos

    Thread Starter New Member

    Sep 19, 2012
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    0
    I have a scheme for modulator. frequencies that were obtained from the simulator for "1"=(680hKz - 691kHz), "0"=(669kHz - 675kHz). Frequencies are variable over the time. Now I need scheme for FSK demodulator, which worked for this frequencies. Is it a good solution IC NE564? Scheme for modulator and datasheet for IC NE564 are attached.

    http://www.datasheetcatalog.org/datasheet/philips/NE564.pdf
     
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