Discussion in 'General Electronics Chat' started by Mathematics!, Jan 20, 2010.

  1. Mathematics!

    Thread Starter Senior Member

    Jul 21, 2008
    Is their away in LTSpice to set an input rf signal so I can test my
    FM detectors I am creating in LTSpice?

    I know somebody showed me once how to set a wave file source for an input signal for LTSPICE to use but is their away to set an RF signal instead of a wave file.

    I have a dummy fourier series equation/approximation of a RF signal I want to use for an input to the FM detector circuit...Is it possible to set the input signal in LTSpice using an math equation because wave file won't get up to a 120MHz ....etc carrier frequency...etc

    If LTspice cann't do this then is their any free easy to use software that I could use to test me FM detector is working correctly before I start trying to build/etch/drill/solder everything together.

    Thanks for your help
    I would really like to use LTSpice to do everything.
    I am testing the foster-seeley detector from a pervious post I posted in.
  2. Mathematics!

    Thread Starter Senior Member

    Jul 21, 2008
    anybody know if this is possible
  3. Papabravo


    Feb 24, 2006
    Go to the LTSPICE group on Yahoo. Helmut or Mike will know the answer. My guess is the answer will involve a VCO. The input voltage will sweep the frequency any way you care to describe it.
  4. ifixit

    Well-Known Member

    Nov 20, 2008
    This may work...
    1. Hit 'F2', click on the [SpecialFunctions] menu, select 'modulate' or 'modulate2', and place in schematic.
    2. Drive the FM port with a voltage source that has a wav file as its source. Syntax: Vxxx n+ n- wavefile=<filename>
    or this behavioral source may do everything...

    Syntax: Bnnn n001 n002 V=<expression> [ic=<value>]
    + [tripdv=<value>] [tripdt=<value>]
    + [laplace=<expression> [window=<time>]
    + [nfft=<number>] [mtol=<number>]

    'Laplace' gives me a headache, but hopefully you can figure it out from here.

    Good luck