Crystal Radios

A medium wave broadcast station antenna system generally comprises a ¼ λ vertical element

and earth.

It would not be wrong to infer that such an antenna would be ideal for a crystal radio.

Crystal Radio Antenna Arrangement

However, practical reasons necessitate use of a much shorter element, with a suitable loading

coil making it resonant at the desired frequency.

Good results would be obtained with an element not shorter than 60 feet.