File:Hertzian spark gap transmitter and receiver.png
Hertzian_spark_gap_transmitter_and_receiver.png (594 × 241 pixels, file size: 44 KB, MIME type: image/png)
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Summary
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| Description |
English: A replica of some of the apparatus Heinrich Hertz used in his historic 1886 experiments on radio waves, for use in education, from a 1912 scientific equipment supply catalog. It consists of a spark-gap transmitter (Hertzian oscillator) (left) driven by an induction coil which emits radio waves which were focused into a beam using a metal parabolic reflector, and a coherer receiver (right) in another parabolic reflector. The box (left) contains a storage battery to power the transmitter. Hertz used this apparatus to demonstrate standing waves, diffraction, refraction, and polarization of radio waves.
The transmitter consists of two brass rods with a spark gap between them, suspended at the focal line inside the cylindrical reflector. The rods function as a half-wave dipole antenna, radiating electromagnetic waves in the UHF range. If the rods were roughly 30 cm long, as they appear, the transmitter would generate 60 cm radio waves, corresponding to a frequency of about 500 MHz. The receiver uses a coherer, a primitive radio wave detector. It consists of a a glass tube containing two electrodes with metal powder between them, suspended along the focal line of the reflector. The electrodes are attached in a DC circuit with a battery and electric bell (right). When it receives radio waves, the coherer becomes electrically conductive, and the current from the battery rings the bell. After detection, the coherer had to be switched back to a nonconductive state by giving it a tap. |
| Date | before 1912 |
| Source | Downloaded April 28, 2013 from Physical Apparatus Price List No. 50, Vol. I and II, 1912, Max Kohl A.G., Chemnitz, Germany, p. 1039, fig. 63268A (page image 758) on Instruments for Science 1800-1914 collection, Smithsonian Institution website |
| Author | Unknown author |
Licensing
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This media file is in the public domain in the United States. This applies to U.S. works where the copyright has expired, often because its first publication occurred prior to January 1, 1929, and if not then due to lack of notice or renewal. See this page for further explanation.
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| Annotations | This image is annotated: View the annotations at Commons |
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| Date/Time | Thumbnail | Dimensions | User | Comment | |
|---|---|---|---|---|---|
| current | 10:14, 30 April 2013 | | 594 × 241 (44 KB) | Chetvorno (talk | contribs) | User created page with UploadWizard |
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