In addition, it must be said that for the first 20 years radio was used only by the military and exclusively in the telegraphic mode Of course, if you do not count individual single enthusiasts radio amateurs, engineers and experimenters. ) But I will begin my story with an overview of the types of radio receivers and their quality, which were already known at the end of the First World War… And what were the transmitters of the beginning of the 20th century?