Radio experimenters often need a variable capacitor to tune their circuits, as the saying goes, for maximum smoke. In decades past these were readily available from almost any scrap radio, but the ...

This article is part of The engineer’s complete guide to capacitors. If you’re unsure of what type of capacitor is best for your circuit, read How to choose the right capacitor for any application.

Variable capacitors may be useful, but the air gap that provides their capacitance is their greatest weakness. Rather than deal with the poor dielectric properties of air, some high-end variable ...