2.4 gig sweeper

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

  1. joemaughan1947

    Thread Starter New Member

    Apr 15, 2013
    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


    Mar 31, 2012
    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
    That is interesting, the only thing I have used pin 5 for is to FM the oscilator with audio.
    Joe :eek:)