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'Positive or Negative Shift' ?

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  • 'Positive or Negative Shift' ?

    Can anyone at Sombra-Labs explain what the 'positive or negative Shift' of FM/ppm systems is referring to ???
    Since your receivers have an Auto-detect for that, I thought maybe that would be a fairly easy one to explain?
    Rick L.
    --------------------------------------------
    * Asking Questions is a 'Good Thing',
    Since Learning is Always a 'Good Thing' *

  • #2
    The -ve and the +ve shift refers to the encoding of the stick positions on the PPM frame by the transmitter. Futaba/Hitec uses the -ve shift while JR uses the +ve shift method. When using any of the Sombra receivers you don't have to worry about the shift of your transmitter, as long as your transmitter can output PPM frame, it will work. Hope the above helped answer your question.

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    • #3
      Thanks for the reply.
      I don't think frequency modulation (FM) has shifting voltage levels, so these shifting levels must have something to do with the PPM version of FM, Only? Is this correct?
      Rick L.
      --------------------------------------------
      * Asking Questions is a 'Good Thing',
      Since Learning is Always a 'Good Thing' *

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      • #4
        To simply put the shift has nothing to do with RF, this is the baseband encoding of the PPM frame. The signals from the sticks, pots and switches on your transmitter are PWM (pulse width modulated) signals that are assembled in the PPM frame. To over simplify with digital analogy, you can represent a closed switch by either a zero or a one and vice versa for the open, it doesn't matter as long as you know which one is which on the other end.

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        • #5
          Thanks for trying.
          I still don't see exactly where voltage shifts fit into the picture, but 'It don't Matter'.;)
          All we really need to know is that there are 2 flavors, that can't be mixed, unless we're using an auto-detect receiver, like the Sombra, which will fix Everything :D
          Last edited by toppack; 04-29-2009, 10:12 PM.
          Rick L.
          --------------------------------------------
          * Asking Questions is a 'Good Thing',
          Since Learning is Always a 'Good Thing' *

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          • #6
            You're right, if using Sombra Rx, you don't need to worry about the shift :)

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            • #7
              This has been a very informative give-and-take. I've learned a few things I needed to know. Keep it up, guys.

              David,
              "... well, that takes care of Jorgenson's theory!"

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