This section is from the book "The Boy Mechanic Vol. 2 1000 Things for Boys to Do", by Popular Mechanics Co.. Also available from Amazon: The Boy Mechanic, Vol2: 1000 Things for Boys to Do.
A simple variable condenser for receiving in wireless, which will give good results, was made by a correspondent of Modern Electrics as follows : Each clip on the switch was made of ribbon brass or copper in the shape shown at A, the first one from the joint of the knife switch being the longest and each succeeding one shorter. The handle was taken from a single-pole switch. The case was made of oak and varnished and the condenser was made of tinfoil and thin sheets of mica, 2 by 3 in. in size. After placing the condenser in the case, hot paraffin was poured around It.
Ill: Lever and Clips