Variable capacitors may be useful, but the air gap that provides their capacitance is their greatest weakness. Rather than ...

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 ...

Marked: "JB" on top. An adjustable plunger set in a stand, moves within a glass cylinder into a metal cup at the bottom. Two contacts, one on top plate, the other on the base plate. This may be a ...