A D V E N T U R E S in C Y B E R S O U N DCalzecchi - Onesti, Temìstocle : 1853 - 1922
In 1884 Calzecchi - Onesti, (pron: Kaltzèhkkee Onèhstee) an italian physicist, observed that loosely packed metallic powders are bad electricity conductors until subjected to some external forces such as electric sparks generated by the opening and closing of an electrical circuit, or the presence of inductive fields , or by electrostatic induction. When the coherer is subjected to the influence of a radio wave (and such is the electromagnetic field produced by a spark), probably because of microscopic electric arcs that weld together adjoining metal particles, an electric current can flow from one electrode to the other. In other words the coherer acts like a kind of semi-conductor device, something like a triac or an SCR, where the trigger is a radio wave instead of a current applied to the gate. In later times others went over his discovery and finally applied it to the detection of coded signals such as Morse coded radio broadcasts. Amongst them the American Lodge, [ English - Sir Oliver Lodge - Ed.] who provided the name for the device and in 1890 explained the principle of the micro-welds, the French Branly, the Russian Popov (no, this isn't a joke), and finally Guglielmo Marconi who in 1894, ten years later, made his first experiments on wireless telegraphy using a three-sparks Righi oscillator powered by a Ruhmkorff machine and of course, in the receiver, a coherer connected to the aerial and acting as an off-on switching device). The Poldhu broadcast of 1901 went through a coherer... The wireless was born! Other than that, the coherer has been employed as a storm and earthquake forecaster. In the past there have been quarrels, especially with the French, on the attribution of the discovery. I think that this is nonsense, because scientific progress is not made up of independent facts, but every scientist relies upon its predecessors and adds his own little brick to the building. And, of course, the building belongs to all mankind! Woulnd't it be interesting for an amateur scientists club to put on some experimenting on the coherer's parameters, that is nature of the metal powder (includind mixes of different metals), compression factor of the powder, radio wavelenght and current (DC, of course) applied to the electrodes? Anyone interested can eMail me, his great grandson, at coherer@sapienza.it
Nel 1884 Temìstocle Calzecchi-Onesti, insetgnate di fisica al liceo di Fermo, in una sua macchina pubblicata sul "Nuovo Cimento", descrisse, per la prima volta le proprieta' caratteristiche del suo tubetto a limatura metallica, progenitore del coherer, dimostrando che la limatura, dopo essere divenuta conduttrice in seguito all'azione di una scarica elettrica, tornava al valore di alta resistenza elettrica con un urto meccanico. La sua memoria scientifica venne pero' riscoperta soltando dopo l'invezione di Marconi.
 Schizzo originale di Calzecchi raffigurante il dispositivo per sperimentare la conducibilita' delle polveri metalliche.
also...Diego Verdegiglio, Roma also...http://www.brera.unimi.it/Atti-Como-96/ Guidone.html
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