Hello, SFFM i dont understand

Discussion in 'General Electronics Chat' started by michael1978, Nov 17, 2018.

  1. michael1978

    Thread Starter Member

    Jun 29, 2014
    303
    1
    Hi everyone,

    can somebody explain me about SFFM in ltspice, formula, i am searching in google but i dont find something with examples, so i want to do experiments, with difference frequency, because i build all complete circuit for fm, after i want to build it, already i am bussy with one, i mean i buy all the thing i am just building
    but this i dont understand

    voltage=1V
    carrier voltage FM=10.7MEGHZ
    modulation index = 22.5
    signal = 10KHZ
    what is the formula???
    thanks goodnight….
     
  2. Bordodynov

    Well-Known Member

    May 20, 2015
    2,101
    639
    Be more curious and independent!
    SFFM.png
     
    • SFFM.asc
      File size:
      468 bytes
      Views:
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    ScottWang likes this.
  3. ScottWang

    Moderator

    Aug 23, 2012
    6,618
    1,021
    @Bordodynov
    I just tested the asc file, but they are the same Vpp as +1.0Vp and -1.0Vp, so two waveforms covered became one, win 7, the version of LTSpice is the newest one, I just updated yesterday.
     
  4. ericgibbs

    Moderator

    Jan 29, 2010
    7,510
    1,517
    hi B,
    I get the same result as Scott.
    Using XP Pro, LTS IV.
    E
     
  5. Bordodynov

    Well-Known Member

    May 20, 2015
    2,101
    639
    Yes, V (1) = V (2). You see, so that the lines do not merge, I shifted the first line up to 100mV.
     
  6. Alec_t

    AAC Fanatic!

    Sep 17, 2013
    9,487
    2,296
    You can see the FM effect more clearly if you plot V1 (or V2) and also a 1V 10.7meg waveform (V3), over a 100uS sim time.
    FM.PNG
     
    Papabravo likes this.
  7. michael1978

    Thread Starter Member

    Jun 29, 2014
    303
    1
    Hi, i realy search on nternet, and i am reading that book in biblotheek about radio, is very good book, but he writte about fm, that i deviation and modulation index, i try to calculate but i dont see any correct result,

    because i am asking all long about radio,
    so now i have complete everything, i am just making experiments with ltspice, like i say, i am building a superhet fm 1, after when i finish i am gonna build the second fm superhet 2 from the book wich i show, and third the again superhet fm 3 from one site i found,

    the next step is to jump to arduino:), i have one arduino i try some experiments with basics book and complete arduino pack,

    Thank Mannnnn:):):):):):);)
     
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