Morse code communication using FM frequency

Discussion in 'The Projects Forum' started by StrawberryBro, Mar 17, 2013.

  1. StrawberryBro

    Thread Starter New Member

    Mar 15, 2013
    2
    0
    Hi, I'm new here, I have a little problem, I'll be grateful for the help. It happens that I want to modify the circuit of an FM audio transmitter, so that instead of transmitting audio can transmit a signal to turn off or turn on a switch, and the switch on and off an LED, the idea is to communicate using Morse code using the FM frequency. What could be modified to do this?. What could be change to a conventional radio receiver, so that instead of playing audio, will have a led (for morse code communication)?.

    This is the transmitter diagram.

    [​IMG]

    Thank you.
     
  2. MartyMitchell

    New Member

    Sep 11, 2012
    23
    0
    Why don't you just send audio (like an 800hz sine wave) into the mic portion of the circuit? Use a tone decoder on the FM receiver side to turn your LED ON and OFF so you can copy CW.

    Marty
     
  3. Papabravo

    Expert

    Feb 24, 2006
    10,152
    1,794
    A constant frequency FM signal wont even be detected by the receiver as anything even remotely interesting.
     
  4. StrawberryBro

    Thread Starter New Member

    Mar 15, 2013
    2
    0
    Hello my friend. Because I am new to electronics, so I'm a little frustrated, and for example, I still do not know where to place an oscillator, for wave.

    One question: An oscillator is the only way to send a sine wave?

    Hello my friend. Nice to greet you and I'll be here to share knowledge on electronics and software also. And sorry but I did not understand what you mean.

    A constant FM signal is not always detected by a receiver?
     
  5. absf

    Senior Member

    Dec 29, 2010
    1,493
    372
    An oscillator doesnt have to be a sine wave generator. Pulses or square wave at 800 Hz would also work. Use a NE555 or LM555 and set it up as an astable oscillator would do the trick as well.

    Are you using your FM radio as a receiver or you make your own dedicated FM receiver? You need a tone decoder using NE567 to decode the 800Hz tone and make it flash an LED or you can amplify the tone and play it on a speaker.

    Allen
     
  6. Papabravo

    Expert

    Feb 24, 2006
    10,152
    1,794
    The basis of FM (Frequency Modulation) is that "information" is encoded in the signal my modulating (changing) the frequency. If the frequency of an FM signal is constant (not changing) then there is no information in the signal and consequently there is nothing for the receiver to detect. Is that clear enough?
     
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