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How to Make a Crystal Set Cat Whisker

From the early days of radio through to the Second World War, a cat's whisker was an almost magical thing. A cat's whisker is actually a rectifier, an electrical component that splits radio signals from the plethora of other signals in the air. With little more than a brass screw and a bit of coke, those in the know could create a crystal radio set, whether they were in a bedroom at home or in a Second World War POW camp deep behind enemy lines.

Things You'll Need

Thin phosphor bronze or brass wire
Coke (A derivative of coal, often used in heating stoves)
Brass screw
Brass screw cup
Knife
Small wooden board
Screwdriver
Thin insulated wire
2 alligator clips
Putty

Instructions

- 1
  Carve an indentation, roughly 1/16 inch deep and the width of a pea, in the surface of a small wooden board. Remove any rough edges. Rest a pea-size piece of coke in the indentation.
- 2
  Slip a screw cup over a 3/4 inch long brass screw. Angle the screw at 45 degrees to vertical and rest the tip against the edge of the piece of coke. Screw the screw into the wood until the screw head and cup rest very lightly against the coke.
- 3
  Cut two 6 inch lengths of wire and then strip away 1/2 inch of insulation from each end. Connect an alligator clip to one end of each wire.
- 4
  Wrap the bare end of one wire around the brass screw, between the screw head and the cup. Gently tighten the screw against the coke to trap the wire and hold the coke securely against the wooden board.
- 5
  Twist the bare end of the second wire around one end of a 4-inch long strip of thin phosphor bronze or brass wire. Ensure that the wires form a tight connection. Bend the last inch of the brass wire through 90 degrees.
- 6
  Mount the junction between the brass wire and the insulated wire on a piece of putty so the bent tip of the wire just rests on the piece of coke. The cat's whisker is complete.

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