Receiver for ask modulation

Discussion in 'Wireless & RF Design' started by Mohaamed Yousry, May 10, 2019.

  1. Mohaamed Yousry

    Thread Starter New Member

    Sep 23, 2017
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    hello , i'm trying to do ASK modulation , i've generated a carrier using the circuit attached below , i'm getting a 16 MHz , 3 v p-p sine wave at the emitter , i want to make a simple receiver for my transmitter , i've tried cascading 3 CE amplifiers like in the 2nd attached schematic , but i'm getting no output , how can i design a receiver for this circuit any help is appreciated .
     
  2. bertus

    Administrator

    Apr 5, 2008
    19,395
    3,918
    Hello,

    Did you check if the transmitter is giving any signal?
    What are you using as antenna?
    The receiver has no selectivity at all.
    It will receive all frequencies that are in reach.

    Bertus
     
  3. Mohaamed Yousry

    Thread Starter New Member

    Sep 23, 2017
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    0
    i think it is giving a signal because , my radio gets interference when my transmitter is powered , i'm using 2.5 m of copper wire as my antenna , i'm also connecting output of envelope detector to a LM358 comparator , but i'm getting no signal .
     
  4. bertus

    Administrator

    Apr 5, 2008
    19,395
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    Zeeus likes this.
  5. AlbertHall

    AAC Fanatic!

    Jun 4, 2014
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    I'm pretty amazed that a three stage common emitter amplifier for 16MHz isn't just an oscillator. The fact that it isn't rather suggests the amplifier is seriously lacking gain for some reason.
     
  6. LesJones

    Well-Known Member

    Jan 8, 2017
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    As there is no supply decoupling I think it is almost certain to oscillate.

    Les.
     
  7. Mohaamed Yousry

    Thread Starter New Member

    Sep 23, 2017
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    why would it oscillate ? i thought there needs to be positive feedback for a circuit to oscillate .
     
  8. Mohaamed Yousry

    Thread Starter New Member

    Sep 23, 2017
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    0
  9. AlbertHall

    AAC Fanatic!

    Jun 4, 2014
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    Yes, and unless that circuit was made with very careful routing and decoupling as it would have a gain around 1000, very little signal would need to be coupled back into the input to make another transmitter!
     
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