File:Old coherer radio receiver using an electrostatic machine as transmitter.jpg
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Captions
Captions
Antique coherer radio receiver and Wimshurst machine
Summary
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| Description |
English: An antique coherer radio receiver from the turn of the 20th century (rear). The earliest type of radio receiver, used between 1895 and 1910, this was designed to receive Morse code radiotelegraphy signals from a spark gap transmitter. A modern Wimshurst-type electrostatic machine (foreground) is used to create electric sparks to generate radio waves for the receiver. The receiver consists of a coherer (center), a glass tube containing two electrodes with loose metal powder between them, connected through a tuning transformer (L) between a wire antenna and ground. When a radio signal from the transmitter is received by the antenna and applied across the coherer electrodes, it causes the metal filings to clump together creating a conductive path between the electrodes. The coherer is also connected to a circuit with a battery, relay and electric bell. The current from the battery flows through the coherer and rings the bell. In order to return the coherer to its nonconductive state to prepare it to receive the next Morse code "dot" or "dash" signal from the transmitter, the metal powder must be mechanically disturbed by tapping the coherer. This is done by an electromagnet behind the coherer which pulls a clapper arm over to tap the coherer.
Comment by owner: My rebuilt coherer doesn't work well. It is easy to make the bell ring, even without an antenna, but in most cases the hammer is not strong enough to "decohere" the coherer. To do some day is to rebuild the coherer with nonmagnetic metal particles and straight terminal, and to replate the metals as they originally were. https://www.coe.ufrj.br/~acmq/electrostatic.html By Dr. Antônio Carlos M. de Queiroz (in memoriam). https://www.youtube.com/user/acmdq2007/videos https://acmq-326823.web.app/ https://www.flickr.com/photos/194095199@N08/ |
| Date | |
| Source | Own work |
| Author | DrAntonioCarlosMdeQueiroz |
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| Date/Time | Thumbnail | Dimensions | User | Comment | |
|---|---|---|---|---|---|
| current | 19:06, 21 October 2021 | | 1,920 × 1,080 (216 KB) | DrAntonioCarlosMdeQueiroz (talk | contribs) | Uploaded own work with UploadWizard |
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