Excerpt:
Heinrich Hertz - first to detect radio waves in 1887 by causing a spark to leap across a gap that generated electromagnetic waves - built oscillator and resonator by 1893
Oliver Lodge in Britain, Alexander Popov in Russia, Edward Brauley in France - filled a glass tube with metal filings that would cohere under electromagnetic waves and when the tube was tapped, the filings would collapse to break the circuit - built coherer to detect radio waves by 1894