In 1887,The German physicist, Heirich Rudolph Hertz, put the whole
subject of electromagnetic radiation on a firm basis in a serie
of classic experiments thus establishing the foundation that the
so called radio waves did exist and certainly behave similarly to
light waves in a way they could be reflected, refracted and also
polarized.
As those new Hertzian radiations could not be perceived directly
by human senses, it was necessary to provide some means for detecting
or indicating their presence.
At the beginning of the Electronic age, many physical phenomena
were employed by the reserachers thus originating obscure radio
wave detectors which soon were replaced by crystal or proto-semiconducting
materials.
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Fig. 242 a survey on early types
of devices used for Hertzian radiation |
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