The “Cardboard” Variable Capacitor as built in this article will yield a cap in the range of about 300 pF Max. Increasing it to 7″ will get well up to 370 pF. It is build of readily available material found around the house (some at the hardware store).Link
2 thoughts on “Homemade Simple Cardboard Variable Capacitor”
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I remember from some old electronics books you can also make a variable resistor by shading a solid patch of graphite with a pencil on some paper. The resistance between two leads touching the graphite will vary with the distance between them. You could probably do this on the cardboard for a “surface mount” resistor on the back of the capacitor…