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58691Re: Switching power supplies

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  • Dave
    Nov 2, 2011
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      Take care trying to use old cellphone wall-wart's as "PSU's".

      Many are not PSU's as such, but Chargers. As such, they do not regulate
      well (if at all) with a very light load, such as an SDR.

      Also, those that do regulate, might do so, in a way that changes the
      "mode" of operation of the Switcher itself, from Continuious to
      Discontinuious mode, dramaticaly altering it's RFI spectrum, making any
      filtering it has less effective than it might be in "normal" use..

      Joking apart, sometimes adding extra load to some small (and large)
      SMPS's, can help keep them quiet(er) than they would otherwise be.

      Go for about 30% or more of their nominal rated output. Check on the
      ratings plate, label, embossing, for what they are rated to provide, some
      are suprisingly powerfull, but most are not easy to read that data from.


      Dave G0WBX.
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