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9931Re: [loopantennas] Re: Variable Dielectric Capacitor?

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  • kevin asato
    May 17, 2013
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      Should work. By theory a capacitor is nothing more than 2 opposite potential surfaces separated by a dielectric (air, fiberglass, some sort of plastic, etc). Using square plates will produce very non linear capacitance values as capacitance is affected by the area of the opposing plates. PITA to try to calculate, too! One thing to be aware with what you are planning is that you may have to account for air acting as a dielectric when you insert and remove the polystyrene between the two plates. May not be a large contribution to the overall capacitance but needs to be looked at. Not trying to talk you out of trying this. Let us know how it turns out!

      >My plan is to take two copper clad boards, separate them using plastic spacers (4 or 5mm) and slide polystyrene board between the copper planes.

      I took a basic electricity course seemingly eons ago where we took two sheets of aluminum foil and slightly larger pieces of wax paper. The wax paper was inserted between the foil and the 2nd sheet was laid on top of the foil of what would be the inner surface of the capacitor. The entire assembly was rolled/folded up into a tubular capacitor type form and jumper wires were connected, one to each sheet of foil. The capacitor was then connected to a low current assembly with a known value resistor and an NE-2 neon bulb. We could then see the neon bulb flash at a rate corresponding to the value of the capacitors made by the class. Since this class was geared towards elementary school children, we did not try to calculate/approximate the dielectric value of wax paper, though in retrospect, it would be a good exercise for high school physics.

      73,
      kevin
      kc6pob


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