Wireless Telegraphy: A Popular Exposition (Google eBook)

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Office of "Knowledge", 1902 - Telegraph, Wireless - 104 pages
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Page 103 - he would say. A small reply would come, " I am at the bottom of a coal mine," or, " Crossing the Andes," or, " In the middle of the Pacific.
Page 31 - H) are at right angles to each other and to the direction of propagation. The field stength is given by the RMS value of E in volts/m.
Page 104 - Or, perhaps, in spite of all the callings, no reply would come, and the person would then know that his friend was dead. Let them think of what that meant, of the calling which went on every day from room to room of a house, and then think of that calling extending from pole to pole; not a noisy babble, but a call audible to him who wanted to hear and absolutely silent to him who did not.
Page 104 - ... day from room to room of a house, and then think of that calling extending from pole to pole, not a noisy babble, but a call audible to him who wants to hear, and absolutely silent to all others. It would be almost like dreamland and ghostland, not the ghostland cultivated by a heated imagination, but a real communication from a distance based on true physical laws.
Page 81 - More especially will this system be applicable to enable ships to be warned by lighthouses, lightships or other vessels, not only of their proximity to danger, but also of the direction from which the warning comes.
Page 74 - ... silver, not too finely granulated, and worked up with the merest , trace of mercury. This powder must not be packed too tight, or the action will be irregular and oversensitive to slight outside disturbances, while if too loose it will not be sufficiently sensitive. It is found that the best adjustment is obtained when the coherer works well under the actions of the sparks from a small electric trembler placed at a distance of about a meter. The tube is then exhausted on a mercury pump until...
Page 73 - ... Marconi coherer. The most important part of the receiver is the coherer, which consists of a small glass tube about two and a half millimeters in internal diameter and some four centimeters in length. Two silver pole pieces are lightly fitted into this tube, separated by a gap of about a millimeter, containing a mixture of 96 parts of nickel and 4 parts of silver, not too finely granulated, and worked up with the merest , trace of mercury. This powder must not be packed too tight, or the action...
Page 76 - Small choking coils, kl k1 that is to say, coils wound so as to have self-induction or electric inertia are introduced between the coherer and the relay, their effect being to compel the greater part of the oscillatory current induced in the circuit by the electric waves to traverse the coherer, instead of wasting the greater portion of its energy in the alternative path afforded by the relay. 434. WIRELESS TELEGRAPHY. Marconi coherer. The most important part of the receiver is the coherer,...
Page 62 - ... far more conclusive than mine, although he used a much less effective receiver than the microphone or coherer. I then felt it was now too late to bring forward my previous experiments ; and through not publishing my results and means employed, I have been forced to see others remake the discoveries I had previously made as to the sensitiveness of the microphonic contact and its useful employment as a receiver for electric aerial waves.
Page 61 - ... a telephone. This led me to experiment upon the best form of a receiver for these invisible electric waves, which evidently permeated great distances, and through all apparent obstacles, such as walls, &c. I found that all microphonic contacts or joints were extremely sensitive. Those formed of a hard carbon such as coke, or a combination of a piece of coke resting upon a bright steel contact, were very sensitive and self-restoring ; whilst a loose contact between metals was equally sensitive,...

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