Crystal radios or cat's whisker sets were widely used in the early 1920s as broadcast receivers.
Although these early crystal sets or cat's whisker radios employed no amplification, a reasonable signal could be gained by using an external wire antenna.
As a result many of these wire antennas could be seen out of the back of houses around the country.
Note on How a Crystal Radio Set Works:
The crystal radio is a simple form of radio using just a few components. Its operation is easy to understand it it provides an excellent basis for understanding how more complicated forms of radio work.
Read more about how a crystal radio works.
Crystal radio / cat's whisker sets
There was an enormous variety of crystals sets or cat's whisker radios that were manufactured for the domestic market in the 1920s once radio broadcasting had become established.many of these crystal sets were sold as complete radios, but there was also a booming market in kits and the components. Many people made their own radios at home.
Other sets were manufactured commercially, and the finish on these was often, but most certainly not always better.
One popular approach to enclosing the crystal sets was to use a wooden box with a cover. This meant the crystal set / cat's whisker radio could be closed to prevent damage of any accidental change of the dials and settings.
Other radios were left open, and showed some of the excellent components used. This particular one below shows the magnificent capacitor used.
Other crystal sets had coils that were mounted above the panel. This example shows the coil, cat's whisker detector and a switch, obviously for band-switching, along with the tuning capacitor control.
End of the crystal radio
As the number of broadcast stations began to increase, so did the requirement for greater levels of performance. Both improved selectivity and sensitivity were required.
As indirectly heated valves or vacuum tubes became available, this considerably reduced the running costs of these radios as large batteries were no longer required - they could be run from mains electricity.
Also the superheterodyne radio started to become popular as it offered significantly better levels of selectivity and sensitivity. As a result, the crystal set or cat's whisker radio started to decline in use from the middle of the 1920s and early 1930s. By the end of the 1930s few crystal sets were in use.