Crystal Sets

Crystal Sets: General

Crystal sets became widely used in the 1920's with their crystals, cat's whisker and point contact providing hours of amusement, and that before the broadcast station was picked up!

The point contact between the crystal and a metal wire or "cat's whisker" formed a semiconductor junction.

Circuit Diagram An early design of circuit is shown. Far from ideal, it still provided reception within a few miles of the transmitter providing the aerial was long enough - the length of a garden being about right!

The Crystal

Usually galena, lead ore, this provided the semiconductor rectified needed for the radio "detector". Although the crystal had no magical ability (just a physical property) this did not stop the manufacturers making some outlandish claims, see the tins for details!

Some Early Crystal "Tins"

The tins would contain one or more crystals and sometimes a pair of tweezers and instructions.
Dr Cecils Crystal

A later crystal in a box, possibly of U.S. origin?

Instructions!

The Coil

The simplest sets had just a coil to tune to the desired frequency. With few transmitters around this would work, just, and had the cost advantage of not needing a variable capacitor.

The Brownie II was of this simple design. The knob at the front moved a slider along a coil. The closer the slider moved to one end the worse the performance.

Circuits soon began to use a fixed coil with a variable capacitor.

The Headphones

The headphones were of necessity high impedance devices which meant that a crystal set was essentially for personal use. Ingenious designs appeared to amplify the audio signal.

The Valve Set

Valve (tube) wireless sets soon became the norm offering signal that all the family could hear and removing the need for the listener to patiently find the right spot on the crystal.

The Magic of Crystal Sets

Crystal sets did live on from the 1920's into the 1930's not least because they were simple, cheap and needed no batteries. Crystal sets were also popular with the young radio enthusiast as they were so simple to build. In fact crystal sets are still built by enthusiasts and for educational purpose today.

The crystal set was magical. It allowed a whole audience to gain access to the exciting new media of the day. Perhaps not unlike the "sets" discovered in the early 1990's; that gave rise to the internet audience.

A 1920's commercial crystal set can be seen in detail on the radio shelf. More crystal sets can be found in the gallery.

Trivia Quiz: What was "point contact" ?