US1213250A - Means for receiving intelligence communicated by electric waves. - Google Patents

Description

G. W. PICKARD.

MEANS FOR RECEIVING INTELLIGENCE COMMUNICATED BY ELECTRIC WAVES.

APPLICATION FILED NOV. a. 1906.

1,21 3,250. Patented Jan. 2:}, 1917.

UNITED STATES PATENT OFFICE.

GBEENLEAF WHITTIER PICKABD, OF AMESB'URY, MASSACHUSETTS, ASSIGNOB TO WIRELESS SPECIALTY APPARATUS COMPANY, OFNEW YORK, N. Y., A CORPO- RATION OF NEW YORK.

MEANS FOR RECEIVING INTELLIGENCE COMMUNICATE!) BY ELECTRIC WAVES.

Specification of Letters Patent.

Patented Jan. 23, 1917.

Original application filed August 30, 1906, Serial 110,332,697. Divided and this application filed November 8, 1906. Serial No. 342,465.

T 0 all whom it may concern Be it known that I. Glmnxnnnr \Vnrrrrun PICKARI), a citizen of the United States of America, and a resident of the town of Aniesbury, State of lilassachusetts. have invented certain new and useful Improvements in llleans for Receiving Intelligence Communicated by Elect ric \Vaves, the principles of which are set forth in the following specification and accmn ninying drawings,

which disclose the form of the invention which I now consider to be the best of the various forms in which the principles of the im'ention may be embodied.

This application is a division of my application Serial Number 332,697, filed August 30th. 1906, whieh issued as Patent Number 836,531 on November 20th, 1906.

This invention relates to means for receiving intelligence communicated by electric waves.

The particular inventions claimed in this divisional case relate to the novel coiiper ative. combination of the condenser C1, Figure 1, with the type of detector specified in the claims, and with the (lirect-current indicating instrument.

The object of the invention is to provide "a commercially useful means for operating a device'for translating the connnunications into lntelhglble form, exclusively by the energy of the oscillatory current generated by the receipt of the waves.

' bodied in the local circuit branched off from inductance L, this being the apparatus with which the invention has'been actually used. Figs. 2 and 3 are a side elevation and section respectively of the present preferred embodiment of the detector employed in the invention in its lliltfitflt most eflicient form, Fig. 3'being a slightly modified form.

In Fig. 1 the general arrangement is the well-known loop form of wave-intercepter able in both the wave-intercepter and oscillation-receiving circuits, the inductance L,

adjustable in the wave-interceptor circuit, and the connections of the latter circuit to ground at G,

In Fig. 1, the circuit L, T J, C, T receives the oscillations generated in the waveiutercepting loop, the inductance L being adjustable in the oscillation circuit, which is well adaptedfor use with the disclosed type of detector, as it includes the adjustable condenser C and the device T in shunt to this condenser. The device T is preferably a telephone receiver and may be any other form of device such as a sensitive galvanometer which will indicate an abrupt flow of direct current. The detector, should in use he maintained in good electrical connection in the oscillation circuit and the junction T J should also he a good electrical contact. The lead to the shunt-connected condenserC and the telephone T is taken from a part of the inductance L which is of lower. potential with respect to the ground; the advantage of this arrangement of receiving means being that it obviates the establish ment of a deleterious local condenser-action which would otherwise take place in the leads to and the windings of the indicating device if connected in a circuit through the detector.

A further advantage-of the arrangement is that the proximity to the human body of the telephone or other indicating device does not affect the tune of the circuit A, A as it does not form a deleterious shunt path to ground including the variable capacityof the human body across the inductance L of said antenna circuit, owing to the fact that the potential of the circuit between the de tector and the lower inductance connection is. during the receipt ofthe oscillations and with respect to them, of the same potential as that of the earth.

The detector roughly indicated at T J in Fig. 1 is shown in detail in Fig. 2. 1 is a wooden base to which are secured an angular metal support 2 and a metal plate 3, provided with binding posts 4, 5 for the leads of the Oscillating circuit of Fig. 1. One element of the detector is the chuck which is removably screwed into the plate 3 by the part 6. This chuck consists of a piece of metal M to which is soldered a metallic plating M P, such as copper or silver, which plating is deposited on the material N in order to provide a large area of surface contact between them with respect to the area of the junction T J of Fig. 1. The deposition may be by electro-plating or by fusing a layer of the material N upon a metallic surface, or otherwise; and as shown in Fig. 3, itis sufficient to place the material N in a liquefied mass of fusible metal F M in a chuck-cup 18, provided with a screw 17,

, so that when the metal F Mcools and solidifies, the material N will be firmly embedded in, and in good electrical contact with the metal F M.

The operative contact-junction (T J of Fig. 1) is located at the lower end of the hollow metallic sleeve 7 of Fig. 2, which junction is of less surface area with the material N than at the surface M P. This sleeve slides along the metallic projection 8 depending from the metallic ball. 9, the ball forming a ball-and-socket universal joint with the part 10 of thin metal, which is stamped to shape and secured to the metallic support 2 so as to complete the circuit.

The sleeve member 7 of the detector may be of any suitable metal which is a good conductor of electricity. The other member N of the detector should consist of a material having thermo-electromotive power and a high electrical resistance in order to convert or rectify the oscillations into unidirectional pulses. The junction between the members N and 7 should be a good electrical contact, and this is secured by the spring 11 which presses the sleeve contact against the member N. This should be a good electrical contact in order to permitthe energy of the received oscillations to have ready access to the junction, and to eirclude all varying-rcsistance action of a loose-contact or coherer nature which, if it occurred, would offer serious opposition to the electromotive forces set up by the received oscillations and thereby prevent the flow of the feeble oscillatory currents which, if not so opposed, are converted into direct electromotive forces in which form the energy is used to operate the indicating instrument.

The member 7 of the detector may be metallic, but the best results so far have been had with the member N of a non-metallic natural element such as silicon which possesses in a' high degree the desired properties of high electrical resistance and high thermoelectromotive power. It appears to be most useful either in the massive amorphous or graphitic solid form. This material may be used commercially when pressed into good electrical contact between two good conductors such as copper, irrespective of the apparent relative surface areas. But this is not the mostsensitive form because two operative detector-junctions may be formed, one at each contact of the material with the two conductors. The combined electromotive forces at these two junctions act in opposition to each other with respect to the telephone, and if the two junctions are of equal eflicien'cy, the result will be a complete annulment of any useful action. In practice, however, it is impossible to obtain equal efiiciency of each junction by connecting the simple material between two conductors in the circuit, and hence the action will always be so much greater at one junction that there will exist a suflicient preponderance of electromotive force of one sign to operate the sensitive in icating device T of Fig. 1. However, by roviding a relatively very large area of surface contact at. the junction which it is desired to make of less or no efficiency, as by the metal plating or embedding in Figs. 2 and 3, it is possible to obtain nearly all the electromotive force as of one sign, and this is the preferred embodiment of the invention.

In order to obtain the best results, the above specifications should be carefully followed. In such case the operation is that the energy of the oscillations is rectified, i. 0,, the oscillations in one direction are converted into a direct electric current-that is into a series of unidirectional impulses having the same frequency as that of the oscillating currents. The reason for the fact, hereinbefore stated, that the circuit of the detector is well adapted, by the inclusion of condenser C for use with the disclosed rectifying detector, is that the condenser, adjustable by the operator for best results as indicated by the intensity of sound from the telephone diaphragm, has one side charged by a plurality of rectified highfrequency unidirectional impulses from the detector, this accumulated charge being discharged into the telephone winding at a lower order of frequency which is adapted to cause the most cflicient vibration of the telephone diaphragm; it being a well-known fact. as described hereinafter, that a telephone cannot be operated commercially by currents of high frequency.

So far, I have been able to convert upward of ten per cent, of the energy of the oscillations into direct current energy. The device is therefore an electrical converter or rectifier, and inasmuch as the potential of the regenerated direct current is different from that of the oscillations, it is an electrical transformer.

In the preferred form of the invention,

the invention, it will, however, have no other efl'ect except to decrease the useful rectifying action, because such resistance-varying action cannot alone, without auxiliary electromotive force operate an indicating device, and because no auxiliary source of electromotive force can be used with the detector of this invention which such resistance-variation n'iight vary to operate thetelephone. Trials have demonstrated that the use of an auxiliary source of electromotive force with this detector results in an annulment of all effect of the energy of the oscillations upon the telephone, that is, an annuln'ient of the rectifying action, and that any resistance variation which might take place was inoperative as to the auxiliary source, to produce an indication in the telephone.

The remarkable fact that the telephone can be operated in a commercial manner solely by the converted energy of the received oscillations, is explained by the statement that that feeble energy which is received at the ordinary commercial wireless telegraph station is amply sufficient to operate a sensitive receiving instrumei'it. provided that the translation of this energy into the form of a direct current is efiiciently at? complished, and particularly a form of direct current, which, if consisting of separate pulses, has a frequency of a lower order than that of the received oscillations. in order to operate the telephone. It is, of course, necessary in commercial work, to effect this conversion, if the use of imperfect contact detectors with an auxiliary source of energy is to be obviated, because there is no known indicating means which can be sensibly affccted by the received energy of commercial long distance wireless telegraphy when in the form of high frequency oscillations, notwithstanding the fact that a sensitive tele phone may, as an experin'iental feat, be slightly affected by the oscillations emitted from a nearby or very powerful sending station.

The energy rct' uircd to commercially operate a telephone. that is, to produce in it a clearly defined dot, in, for example, the Morse code, is approximately onemillionth (1X10") erg. The energy received by the average long-distance commercial wireless telegraph station is of the order of magnitude of one-thousandth of an erg per dot. The efiiciency of the apparatus of this invention, as demonstrated by trial under commercial conditions, is upward often per cent. There is thus ample margin for commercial operativeness for the least sensitive form of this invention in the case of the present longest distance wireless teleg 'aphy.

The speed'of reception with this invention is unlimited, since the detector is not'only self-restoring to its sensitive state, but this restoration is practically instantaneous be cause the small quantity of heat which is generated by the received oscillations which are substantially stopped by the detector comprising a signal is rapidly conducted away so as not to deleteriously affect the rectifying action.

The advantages of the new detector are as follows: It fulfils all requirements of commercial wireless telegraphy as to sensitiveness, speed, stability and freedom of delicate adjustments. I have found that the continued sensitiveness of the detector is in no wise impaired by severe static discharges. It is also simple and cheap in construction. It is not affected by changes in atmospheric temperature or humidity. Its sensitiveness so far has not been impaired by continuous and continued use.

Any portion of any one of the classes of material having high thermo-electromotive force and high electrical resistance included within this invention, makes an operative contact iunction with a metallicconductor it held in good electrical contact therewith. This invention requires no auxiliary source of heat as has been necessary with previous converters designed for high frequency oscillations. It is an important practical as well as economical advantage of this invention that it essentially dispenses with aux? iliary sources of energy, in that such sources,

such as batteries and the requisite accompanying potentiometers, are expensive in initial cost and in maintenance for operation and repairs, and require frequent replacement. Thereis apparently no limit to the operative life of the detectors included in this invention.

I claim:

1. Means for receivingintelligence communicatedby electric waves, which comprises ,a circuit arranged to be supplied with oscillating current containing energy derived from said waves; a conducting solid connected in good contact in said circuit and constructed and arranged to function as a rectifier to convert said supplied oscillating current into direct currents; and a condenser and a parallel-connected telephone also connected in said circuit, substantially" as and for the purpose described.

2. Means for receiving mtelhgence com munlcated by electric waves, which com prises an aerial wave-intercepting circuit containing an inductance cooperatively related to ground; a circuit receiving oscillating currents from said wave-intercepting circuit by way of said inductance; a con ducting solid connected in good contact in the latter circuit at a point of relatively high potential and constructed and arranged to function as a rectifier to convert said supplied oscillating current into direct cur rents; and a condenser and a parallel-connected telephone connected in said circuit at a point of relatively lower potential, substantially as and for the purpose described.

3. Means for receiving intelligence co nniunicated by electric waves. which co1nprises an inductance coil constituting an element of a wave-intercepting oscillating-current circuit which is cooperatively related to the ground and arranged to be supplied with energy derived from such waves; in combination with a condenser connected in a circuit arranged to be supplied, by way of said inductance coil. with oscillating currents also containing energy derived from said electric waves; a device connected in series with said condcnseand consisting of an electrically-conducting but highly-resistant non-metallic material possessing thermo-electromotive power. and thereby functioning as a rectifier of said supplied oscillating currents; and a device connected to receive and constructed to indicate the low of direct currents which results, by the functioning of said rectifier and condenser, from said supplied oscillating currents, substantially as and for the purpose described 4. Means for receiving intelligence coinmunicated by electric aves, which comprises an inductancecoil constituting an element of an oscillating current circuit which is arranged to be supplied with energy derived from such waves; in combination with a conilenser connected in a circuit arranged to be supplied. by ay of said inductance coil, with oscillating currents also containing energy derived from said electric waves;

a device connected in series with said condenser and consisting of an electrically-con ducting but highly-resistant non-metallic material possessing thermo-electromotive power, and thereby functioning as a rectifier of said supplied oscillating currents; and a device connected to receive and constructed to indicate the flow of direct currents which results, by the functioning of said rectifier and condenser, from said supplied oscillating currents, substantially as and for the purpose described.

5. Means for receivingintelligence coinmunicatcd by electric waves, which comprises a condenser connected in a circuit which is arranged to be supplied with oscillating current containing energy derived from such Waves; in combination with a higha'esistance device connected in series with said condenser and constructed and arranged to function as a rectifier for said supplied oscillating current; and a device connected to receive and constructed to be operated by the flow of direct currents which results, by the functioning of said rectifier and condenser, from the supplied oscillating current. substantially as and for the purpose described.

6. Means for receiving intelligence communicated by electromagnetic waves, which comprise a circuit constructed and arranged to receive oscillations resulting from such waves, said circuit including a rectifying conductor in effective rectifying contact therein, whereby a portion of the energy of said oscillations is converted into direct current pulses: a direct current indicator con nected in said circuit for operation by said direct current pulses; and means in said circuit for permitting the passage of oscillations through said rectifying conductor and in shunt to said direct current indicator.

GREENLEAF WHITTIER llCKAltl).

\Vitnesses:

EDWARD H. RownLL, MYRA S. Row ELL.

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