2.4 gig sweeper

Discussion in 'Wireless & RF Design' started by joemaughan1947, Apr 15, 2013.

  1. joemaughan1947

    Thread Starter New Member

    Apr 15, 2013
    2
    0
    Into HSMM-MESH big time and wanted a way to see where my antennas or other devices really were spectrum wise.
    Therefore, I am building my own poor man's spectrum analyzer.
    I actually have one running now but I recognize that it needs to be better.
    Not being very smart on these things and not an engineer but having been exposed to such things enough to be encouraged I have put together a 2.4 gig VCO swept by a 555 generated constant current charged saw tooth.
    Running between 1/3 and 2/3 VCC, which is not what I wanted, I need 2 volts to 15 volts P/P. Or 2 to 17 volts depending on which VCO you get.
    Since the VCC spec on the 555 is 18 volts max I am taking a risk with running it at 24 volts VCC in order to get the 2/3 VCC top rail of 16 volts so I cringe every time I apply power.
    I don't like taking the sweep voltage from the charging CAP because it has to feed both the VCO and the horizontal input of the scope.
     
     
    So I need some advice on how best to amplify, split, match the sawtooth.
    My first impression is to add an OP AMP but that is where the problem is.
     
     
    Thanks, Joe :eek:)
     
  2. WBahn

    Moderator

    Mar 31, 2012
    17,715
    4,788
    You can use the control input to change the voltage divider away from the 1/3 and 2/3 points.

    If you have a good sawtooth and it just isn't between the desired endpoints voltage-wise, then I would recommend passing it through a little opamp circuit that provides the needed gain and offset correction to get what you want.
     
    joemaughan1947 likes this.
  3. joemaughan1947

    Thread Starter New Member

    Apr 15, 2013
    2
    0
    That is interesting, the only thing I have used pin 5 for is to FM the oscilator with audio.
    Joe :eek:)
     
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