Yesterday, we presented a homemade headphone from a hundred years ago, from the October 1919 issue of Radio Amateur News. That issue also contained a number of other homemade parts, such as the variable grid leak resistor shown above, submitted by the aptly named Arno Kluge. The part is made on bakelite or rubber, and the resistance is formed by a line of India ink traced with a compass.

The magazine also contained two capacitors, one fixed and one variable.  The fixed condenser is made using sheets of mica as the insulator.  For those wishing to make a reproduction today, the best source of mica would probably be the waveguide cover from an old microwave.

The variable condenser is made from two tubes.  In this case, the author used parts from an old bicycle pump.  The inner tube is shellacked, then covered with wax paper, and then shellacked again.