Card Radio

Among some of our modern contemporaries, ‘musical’ postcards evoke strong reactions of astonishment about hypermodern microcontroller technology. However, such flat melody memories would only have elicited a weary smile from our forefathers. As early as 1928, there are reports that radio cards with the dimensions of a regular postcard and a thickness of only a few millimetres were being made. These cards concealed a basketwork coil with a sliding tap for tuning the frequency of the received signal, a fixed capacitor and a miniscule detector device consisting of a small crystal with a ‘whisker’ contact.