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Need help connecting a spectrum analyzer to a breadboard

Discussion in 'Radio and Communications' started by aries, Aug 18, 2011.

  1. aries

    aries New Member

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    Please can anyone tell me how to connected the bread board to spectrum analyzer. I have made a circuit of low pass filter on bread board and i want to see the frequency response on spectrum analyzer. what do i have to do? i have a cable whose one end is connected to the spectrum anlyzer input and second end is a BNC. what to i have to do to connect to a single wire coming from bread board to sectrum analyzer?
     
    Last edited by a moderator: Aug 23, 2011
  2. JimB

    JimB Super Moderator Most Helpful Member

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    A spectrum analyser on its own will not show the frequency response of a filter.

    To show the frequency response, the analyser must be used in conjunction with a tracking generator.

    What sort of filter is this?
    An audio filter or an RF filter?

    JimB
     
  3. aries

    aries New Member

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    @JimB

    It is an RF filter. I do not have a tracking generator. Without tracking generator It means I cant see the frequency response on spectrum analyzer?

    Please guide me how to connect a single wire comming from a simple breadboard to spectrum analyzer without Tracking generator?

    Is it necessary to connect tracking generator.?

    If I have a spectrum analyzer with builtin tracking generator than how can i connect a single wire comming from breadboard to signal generator
     
    Last edited: Aug 19, 2011
  4. dave

    Dave New Member

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  5. Nigel Goodwin

    Nigel Goodwin Super Moderator Most Helpful Member

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    You don't have a single wire from the filter, you have two wires, the signal and ground/chassis - exactly as you would with an oscilloscope.

    I wouldn't have thought you would need a tracking generator woith a spectrum analyser, just a white noise source.
     
  6. aries

    aries New Member

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    @nigel
    Exactly 2 wires are comming out. one ground and outher is the output wire. oscilloscope will show in time tomain. I want to see the frequency response of low pass filter. how can i see?
     
  7. Nigel Goodwin

    Nigel Goodwin Super Moderator Most Helpful Member

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    Like I said, white noise generator on the input, spectrum analyser on the output.
     
  8. aries

    aries New Member

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    I am giving input from frequency generator to the filter circuit and output should be connected to the spectrum analyzer. The problem is i have one cable its one end is connected to the spectrum analyzer and second end of the cable is a BNC (MALE) now how can i connect to breadboard.
     
  9. Nigel Goodwin

    Nigel Goodwin Super Moderator Most Helpful Member

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    A piece of screened cable with a female BNC on it - or a scope probe direct from the spectrum analyser.

    However, a frequency generator won't give you the frequency response with a spectrum analyser.
     
    Last edited: Aug 20, 2011
  10. aries

    aries New Member

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    how can i then give the input to my filter circuit as i want to give a 500mV signal to the circuit. u were talking about white noise generator ?? Is this a signal generator??
     
  11. Nigel Goodwin

    Nigel Goodwin Super Moderator Most Helpful Member

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    Kind of, it generates ALL frequencies at the same time, which is called white noise, the spectrum analyser will display which ones get through, giving you the frequency plot you want.

    To do it with a signal generator use a scope instead of a spectrum analyser, and manually measure the output at each individual frequency and then manually plot a graph.
     
  12. JimB

    JimB Super Moderator Most Helpful Member

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    Quite correct, I had initially thought of mentioning a noise source, but decided to keep it simple.
    However, the frequency spectrum of the noise may not be flat across the frequency range of interest.
    It is necessary to compare the noise in and the noise out from the device under test if you are going to go down this route.

    JimB
     
  13. Nigel Goodwin

    Nigel Goodwin Super Moderator Most Helpful Member

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    If you've got a spectrum analyser, then white noise IS simple! :D
     
  14. aries

    aries New Member

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    please tell me from where should i give the noise source cant i give the input to thelow pass filter from frequency generator.
     
  15. aries

    aries New Member

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    @jimB
    I have just got a spectrum analyzer. a probe whose one end is connected to the spectrum analyzer and the other end of the probe is a BNC(male).

    low pass filter which is implemented on breadboard has two wires one for ground and other is the output wire. now how the BNC (male) connector be connected to the output wire comming from breadboard.

    from where do i have to get the white noise signal to give to the input of filter?

    I only have function generator and frequency counter?

    I want to give 500mV signal to the filter input
     
  16. ericgibbs

    ericgibbs Well-Known Member Most Helpful Member

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    hi aries
    Ref our Chat.

    What information do want to know about your 1MHz low pass filter.?

    Do you want to plot the response ?
     
  17. aries

    aries New Member

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    yes ericgibbs i want to plot the frequency response and i m using a spectrum analyzer to see the response. still i have confussion in giving input to the lowpass filter having cutoff frequency 1MHz. and connecting the filter output to the spectrum analyzer.

    Any alternate available for seeing the response?
     
  18. aries

    aries New Member

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    No spectrum analyzer does not have a white noise output m using IFR 2395 model spectrum analyzer. I am using spectrum analyzer for the first time so dont have any idea
     
  19. ericgibbs

    ericgibbs Well-Known Member Most Helpful Member

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    hi,
    Do you have a dual channel oscilloscope.? and a sine wave signal generator that will work upto 1.5MHz

    http://en.wikipedia.org/wiki/Low-pass_filter

    EDIT:
    Look thru this pdf.
     

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    Last edited: Aug 21, 2011
  20. aries

    aries New Member

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    @ericgibbs

    Yes i do have a dual channel oscilloscope and a function generator having frequency upto 5 MHz.

    but the oscilloscope is in time domain. For frequency response the x-axis is a log frequency scale.
     
  21. ericgibbs

    ericgibbs Well-Known Member Most Helpful Member

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    You can still plot the frequency response of the LPF using the scope and sine wave generator, in the way I explained on chat.

    The 6db point on the Bode plot will be when the output voltage is half the input voltage, the just read off the frequency from generator scale.

    Can you post a digram of your low pass filter.?
     

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