How-To: Air-Variable Capacitor From Scrap Aluminum

This lovely hand-made component, built as part of a crystal radio set Instructables user Jezan assembled for his son, started out as a sheet of 1.5 mm aluminum that looks like it may have come from the side of an old file cabinet. Jezan used minimal tools, laying out the part profiles by hand with a ruler and a compass improvised from a scrap of wood and a pair of nails. The parts are cut out with heavy scissors and re-flattened by pounding with a rubber mallet, then stacked and turned as a group on a hand drill to smooth and polish their edges. The mount was scavenged from a junk television and insulated with plastic cut from old jar lids, while the insulating bushing for the rotor is cut from a plastic pen cap.