Marker Gen square wave

Discussion in 'General Electronics Chat' started by hampton, Jul 15, 2012.

  1. hampton

    Thread Starter New Member

    Jul 5, 2012
    3
    0
    Using a square wave in a marker generator. Should the square wave be symmetrical ? What are the benefits of having it symmetrical ?

    TU,

    Vern
     
  2. wmodavis

    Well-Known Member

    Oct 23, 2010
    737
    150
    Does it add mark on positive transition, negative transition or both? Why are you using it to mark? Do you care about the interval between marks? How are you connecting it to the signal being monitored?
     
  3. hampton

    Thread Starter New Member

    Jul 5, 2012
    3
    0
    Does it add mark on positive transition, negative transition or both?

    I may wish I hadn't asked? I can't answer the above question. I "don't care" may be a proper response.

    Why are you using it to mark?

    To pin point a given frequency within reason.

    Do you care about the interval between marks?

    Yes, several intervals. Using a crystal, counting it down and tapping the interval of interest. Then create a short pulse off the edge of the sqr wave to generate the harmonics.

    How are you connecting it to the signal being monitored?

    Couple it to a coax line with capacitive coupling.

    Remember I am asking what the effect of a non-symmetrical sqr wave on the harmonics it creates?

    Have I answered your question - I hope?

    TU Vern
     
  4. bertus

    Administrator

    Apr 5, 2008
    15,647
    2,346
    Hello,

    Basically a frequency marker is a stable frequency source with a square wave output signal.
    They often have well known frequencies like 10 kHz, 25 kHz, 100 kHz etc.
    They use a square wave to have as many as possible harmonics of the marker.

    Bertus
     
  5. crutschow

    Expert

    Mar 14, 2008
    13,001
    3,229
    A non-symmetrical square-wave will have slightly different harmonic structure which can be calculated as a pulse waveform. See this versus this.

    If you are concerned about the difference you can generate an exact 50% duty-cycle by dividing the square-wave frequency by 1/2 using a flip-flop. Of course, you have to increase the input frequency by two to get the desired output frequency with this scheme.
     
  6. hampton

    Thread Starter New Member

    Jul 5, 2012
    3
    0
    Thanks all. I am better informed.

    Vern
     
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