After Hertz found out how to make and receive waves it would still take a long time for radio to find its 'form'. With form I mean the predominant type of social usage of radio waves combined with a specific technological appearance or, in German die apparative Form (apparatic form). Radio, as any mass medium, exists on two different layers, as an imaginary social signification and in its distinct appearance as a 'thing'. I use the term social imaginary significations as closely as possible in the way Cornelius Castoriadis proposes it.