Superheterodyne receiver

Up to now, operating a radio required a specialized radio engineer but this changed when Armstrong devised a way to lower the frequency of transmitted radiowaves and amplifying them. This innovation made radios easier to use, paving the way for widespread home use and mass communication.
 Edwin Howard Armstrong United States 1917 Superheterodyne receiver

Up to now, operating a radio required a specialized radio engineer but this changed when Armstrong devised a way to lower the frequency of transmitted radiowaves and amplifying them. This innovation made radios easier to use, paving the way for widespread home use and mass communication.