Crystal radios

I dedicate a section of this web site to the crystal radios.
These small radios can work without any power supply system, don’t needs any batteries or power supply.

The listening is possible only through headphones, needs a good aerial and, of course, you can receive only local broadcasters.

The radio is composed by a tuning circuit, to pick up the electromagnetic waves, and a detector which is used to convert the electrical signal into low-frequency sound audible through headphones.

The tuning circuit it’s composed by a coil and a variable capacitor or, in the oldest models, by a variometer.

The detector is a galena crystal mounted on a base, which could be made in different shapes, and a filiform pointer connected to a lever.

Moving the pointer lever with the hand, it’s possible to find the best contact with the crystal and obtain a good reception.

The crystal detector operation was very precarious, usually during the reception you need to move the pointer several times to be able to have an acceptable listening.

With the advent of semiconductors, after 1950, a germanium diode was used instead of the crystal to obtain a better and more stable listening.

Today a lot of medium-wave broadcasters stations has been closed; the power of those remaining has been greatly reduced so now it’s very hard to operate with these sets.
In these pages you can see photos of different crystal radios.
Some of these were produced by companies and one of them was home-made(or perhaps made by small artisan).

      Ruma  crystal radio  ( first version )          

      Ruma  crystal radio  ( last version )       

        Beteco   crystal radio                                      

        Ivalek  crystal radio  (with crystal)            

        Ivalek  crystal radio  (with diode)               

       Home made crystal radio