During his classic experiments on electromagnetic wave propagation at the Technische Hochschule, Karlsruhe, Hertz generated radio waves by means of the oscillatory discharge of a capacitor through a loop of wire and a spark gap. A similar circuit acted as a detector. The spark gaps and circuits used by Hertz radiated at wavelengths of 50 cm to 60 cm. Later, in 1894, Righi succeeded in producing electromagnetic waves having wavelengths in the range between 20 mm and 125 mm. Further work by several investigators, including Lodge, Fleming, and Nicols and Tear, extended the range and by 1924 Glagoweda Arkadiewa, utilising a novel form of apparatus, was able to generate waves from 50 mm to 82 μm in wavelength albeit at low power levels. With the invention of the audion, or triode valve, by de Forest in 1906, and the consequential development of valve circuits, alternative methods of generating metric radio waves became available. At the end of the 1910-1920 decade regenerative oscillators of the conventional type and electronic oscillators of the Barkhausen-Kurz and Gill-Morrell types had been described.

Inspec keywords: capacitors; triodes; oscillators; electromagnetic wave propagation; spark gaps; radiowaves

Other keywords: Technische Hochschule; metric radio waves; regenerative oscillators; Righi; Fleming; spark gap; Barkhausen-Kurz; Gill-Morrell types; Karlsruhe; electronic oscillators; triode valve; Glagoweda Arkadiewa; wire loop; valve circuits; audion; Lodge; Hertz; capacitor; oscillatory discharge; detector; electromagnetic wave propagation; Tear; Nicols

Subjects: Electromagnetic wave propagation