CW detection?

Discussion in 'Wireless & RF Design' started by BlackCow, May 4, 2010.

  1. BlackCow

    Thread Starter Active Member

    May 11, 2009
    I built a heartly oscillator circuit that I can turn on and off to send morse code, the only problem is that I have nothing to detect it with besides an oscilloscope.

    Simply put how could I make a CW receiver turn the incoming signal into a nice audible beep?
  2. retched

    AAC Fanatic!

    Dec 5, 2009
    A simple piezo attached to the output should do. If you need more umph, add a transistor.

    Do you have a schematic?
  3. davebee

    Well-Known Member

    Oct 22, 2008
    "What's the Frequency, Kenneth?"

    If the oscillator is audio frequency then you could probably hear it directly, but if it is radio frequency then maybe not.

    You might hear a change in the background hiss if you tried listening to received RF directly, but to get a nice clear beep, you'd probably need more circuitry.

    You could mix the incoming RF with a local RF signal about 1 kHz offset from the received RF, then play the resulting 1 kHz signal through a speaker.

    Or you could detect the RF signal, capture its rectangular envelope, then use that to gate a local audio oscillator on and off to play a beep through a speaker.
  4. PRS

    Well-Known Member

    Aug 24, 2008
    One method: Build an antenna that drives a tuned amplifier having a center frequency the same frequency as the transmitter. Have its output drive a trigger that turns a 1kHz oscillator on and off. This oscillator drives your earphones.

    Another method: Build an antenna that drives one input of an active mixer. Buld another oscillator with a frequency 1000 Hz above or below the transmitter frequency. The output of the mixer should pass through a 1000 Hz filter and drive a 386 audio amp which in turn drives your headphones.
  5. bertus


    Apr 5, 2008