US1602085A - Radio receiving system - Google Patents

Description

Oct. 5

Filed April 10 1920 Pigl 4 Sheets-Sheet 1 7kM/smrn/ve r STAT/0N X HEcE/vuva 5 6 4 E APPARATUS WW m //7/7/ 5 2 HEcE/w/va 4 E APPARATUS J W W/ //W2 Pi .3 s B 3 H 2 C 5 H l Z l C g I u G i F i I z; 5 l J DISTANCE ALONG ANTENNA Inventors -Che$ter W.Rice, Edward W.Ke||og5 Their fittorneg.

Oct. 5 1926. 1,602,085

C. W. RICE ET AL RADIO RECEIVING SYSTEM Filed April 10, 1920 4 sheets sheet 2 F1 .4 I RECEIVING. JM-Mg FMfi 8 a 8 7, 8

APPARATz/s fiEbE/V/NG I I v Armnnrus I I i J J 4 I v Inventors 5 Their J tto'rne y.

Oct. 5 1926. 1,602,085

c. w. RICE ET AL RADIO RECEIVING SYSTEM Filed April 10 1920 4 Sheets-Sheet 4 RECEIVING W t: L:-

APPARATUS la AnT/F/c/AL LINE 1 .7 I 2 Pi 12. Fi 15. 6J- 9? A 48 2 R5051 v/ N6 APPA RA 7115 Inventors: Chester W Rice Edward W. Kellogg w fi m/L1,

Patented Oct. 5, 1926.

UNITED STATES PATENT OFFICE.

CHESTER W. RICE AND KELLOGG, OF S CHENEGTADY, NEW YORK, .AS-

SIGNORS TO GENERAL ELECTRIC COMPANY, A CORPORATION OF NEW YORK.

RA DIO RECEIVING- SYSTEM.

Application filed April 10, 1920. Serial No. 372,938.

Our present invention relates to radio receiving Systems and more particularly to an improved arrangement of an antenna for receiving purposes. q

One of the objects of our invention 1s to provide a receiving antenna which will be q previously been employed for receivingpurposes. 1

In carryingour inventlon into effect we make use of a long horizontal receiving an- I tenna. which may be either in the form of a transmission of the signals to be received.

This antenna is so constructed that electrical waves of signal frequency travel therethrough at a velocity as nearly as possible equal to the velocity at which signaling waves in space will travel along the line, Assuming that the antennaliesparallel to the direction of travel of the signaling waves, this will be the velocity 1 of light. If electrical waves travel through the airtenna at the same velocity as that at which the signaling waves travel along its length the signaling currents induced in the antenna will be very small at the end nearest the transmitting station and increase progressively along the length of the antenna becoming a maximum at the end farthest from the transmitting station.

In case the natural capacityand'inductance of the antenna are not of the proper values to give the desired electrical wave velocity for the signal frequency, it is; posbe characteristic of our invention are set 'forth with particularity in the appended claims. Our invention itself however, both as to its organization and method of operation, together with ways in which the particular objects thereof may be attained will best be understood by reference to thefol lowing'description taken in connection with the accompanying drawing. in which Fig. 1

illustrates diagrammatically one way in which our invention may be carried into effeet by making use of a long horizontal conductor with ground connections at both ends; Fig. 2 shows an alternative in the form of a long loop," Fig. 3 shows typical curves illustratingthe variations in signal strength along the length of the antenna;

Figs. 4 and 5 illustrate some of the ways in,

which the wave velocity on a long antenna may be adjusted Fig.6,shows a long multi- I ,turn loop as one of the methods of carrying our invention into effect; Figs. 7 and 8 il1ustrate methods of adjusting wave velocity on loops; Figs. 9 and 10'il1ustrate two of the possible'ways in which a series of loops may be connected togetherso as to give results of adjusting wave velocity; Fig. 11 shows I an alternative means of adjusting wave velocity and Figs. 12 and 13 'show\ arrange-- ments which may be adopted if the receiving station is not located'on the line of the long antenna..-

In the following general description of our invention we have limited ourselves to describing the phenomena as occurring on a long horizontal antenna of the type shown in Fig. 1 for the sake of presenting the ideas with greatest simplicity. It will be evident to those skilled in the art that the same phenomena will occur on long loops and the general treatment given herein will apply also to that case.

Consider first a simple'horizontal receiving antenna 1 as indicated in Fig. 1, which extends from the receiving station at end 3' cf the antenna towards the transmitting sta tion 6 from which the desired signals are coming. The operation of such an antenna in receiving signals may be explained as follows: Assume that the signaling waves in space are traveling from station 6 in the dir because of the losses in the antenna. 7

lower these-losses are the greater W111 be the length of antenna which can be used to' rection of the antenna, then at the end 2 of the antenna a small current will be induced which will be propagated as a Wave along the antenna toward the end 3. If the velocity of this small current wave in the antenna is equal to the velocity of the signaling wave in space, this current wave will grow as it approaches the end 3 by continuously absorbing small additional amounts of energy from the ether waves since the two waves are traveling along in, phase with each other. From this analysis it appears that, if the constants of the antenna are such that the current wave travels at the same velocity as the ether wave, the longer the antenna the greater the current which will be received. There will of course be a maximum length beyond which nothing will be gai i ield advantage. Even assuming a zero loss line a length will ultimately be reached when no further increase in signal strength will resuit from increased length because the waves on the antenna will finally reach an amplitude equal to the amplitude of the ether waves, that is, reradiation will balance the received energy. This conditionmay be referred to as saturation. If, however, the velocity of the current wave in the antenna is not quite the same as that of the ether wave then for a certain distance the two waves will add, but a point will finally be reached where one wave will be so far in advance of the other that the two will be in phase opposition. Interference will then occur and the current wave will decrease to zeroand then anew wave will be started and built up. Under these conditions the strength of the signal which will be received if the receiving apparatus is located at the end 2 of the antenna, will be weak, and as the receiving apparatus is moved along' the antenna in the direction in which the waves are moving the signal" strength will gradually increase to a maximum, then decrease to a minimum, and increase again to a second maximum having approximately the same strength as. the first maximum. The distance along the antenna between maximum and-minimum will depend upon the difierence in the velocity of the electric -wave on the antenna and the ether Wave surrounding it in space. If the velocities dilfer very little a long receiving antenna can be used to advantagegbut if the velocities are considerably diflerent there may be no advantage in using a greater length of antenna than that'which will give the first maximum for the desired signal frequency.

Fig. 3 illustrates the variation in current strength in the antenna under the two different conditions of operation which, we have described. In this figure the ordi 1,,coaosenates represent signal strengthand the abscissae represent distance along the antenna. Curve B shows the increase in current strength along the length of the antenna when the current wave in the antenna and .whenthe current wave and the ether wave travel at different velocities. Here the current increases until a maximum is reached at the point D; then increases to a mimimum at point E; increases to a second maximum at point F; and decreases again to a minimum at point G. Since these two maximum points are approximately of the same value it is apparent that for the velocity relations assumed in thecurve C not-hing will be gained in signal strength by using a greater length of antenna than that repre-' sented by the distance AD. Curve H represents the variation in current strength along the length of the antenna for another case in which the current wave and the ether wave travel at difierent velocities. Here the maximum current is reached at the point I and the minimum point is reached at the end of the antenna. Many of-the long antennae hitherto used, employed rubber covered Wire, buried, submerged in water, or on the surface of the ground. These types of construction give low velocity and high attenuation, both of which efiects limit the length of antenna which can be advantageously employed, optimum length of about one-eighth of'a wave length (of the ether waves) having been observed in tests. The

conditions necessary in order to secure the benefits of longer antennae are high velocity and low attenuation.

For signaling waves traveling in the opposite direction, the currents will build up in the same manner. If these are reflected at the end 2, Fig. 1, they will return to 3 and affect the receiving apparatus, giving the antenna bi-directional properties. Reflection may be avoided by grounding the end 2 through an non-inductive resistance 5 of a value equal to or approximating the surge impedance of the antenna; which is,

a where L and O are the inductance and capacity of the antenna per'unit length. By adopting this or any other expedient which 'eliminatesrefiection from the far end the antenna will be given marked unidirectio'nal properties and will be highly selective for signals coming from one direction to the exclusion, not only of signals coming from other directions but to static impulses coming from other directions as well. The greater the length of the antenna compared with the signal wave length, the more sharply directional the antenna will become.

The damping resistance 5 in Fig. 1 might be replaced by a receiving set having an equivalent impedance without impairing the usefulness or unidirectional property of the antenna when used with the receiving circuit 4. If the receiving circuit 4 also has an impedance approximately equal to the surge impedance of the antenna, then a receiving circuit located at the end 2 will receive only signals coming in the direction 32, or opposite to those received by the-receiving circuit 4. A long antenna may thus serve two receiving stations, for signals coming from opposite directions, and there will be no loss of efliciency by thus making the antenna serve a double purpose. maximum efficiency the receiving circuit should be designed to have an effective impedance equal to the antenna surge impedance. i

In accordance with theoretical considerations, if an antenna were'to be freely suspended and if the surface of the earth constituted a perfectly conducting parallel plane, current waves would travel through the antenna conductor at a velocity equal to the velocity of light. In practice, this theoretical condition may be diflicult to ob tain because of. ground resistance and be cause of the necessity for'providing supports for the antenna.

The effect of these supports may be to add shunt capacity to the line without causing any compensating change in the other line constants. The effect of the v excess shunt capacity may be neutralized for continuous waves of a particular frequency, by means of shunt inductances connected at frequent intervals between the antenna and ground. Or the effect of excess shunt capacity in slowing down the rate of wave propagation may be compensated for by the insertion of condensers in series with the line conductors,

thereby neutralizing part of the series inductance and increaslng the wave velocity.

Such'shunt inductances or series condensers should be sufficiently close together (in no case more than Wave length apart)'to give For continuous sinusoidal waves the ap- In fact, for

parent velocity of propagation will be I greater than the velocity .of light for lower frequencies than that for which the line is adjusted, and will be less than the velocity of .light for signals of a higher frequency than that for'which'it is adjusted.

An alternative method of correcting wave velocity on a long antenna consists in the introduction at suitable intervals oflinks of artifical line, which will act in such a way as to retard or advance the phase of the wave. Thus the introduction of a link consisting, of series condensers and shunt inductances will have theelfect of advancing the phase or increasing the average wave velocity for the antenna as a whole, while the introduction of links consisting of series inductances 9' and shunt condensers 10 as shown in Fig. 11 will produce a delay or slow down the average wave velocity of the antenna. For continuous waves the introduction of a delay link slightly less than one wave length long, will by retarding the phase of the wave by something less than one cycle, have an eflect equivalent to advancing the" phase or increasing the wave velocity, while for single impulses or highly velocity give different velocities for different frequencies. based on frequency, in addition to the selectivity offered by reason of the directive properties of the antenna. For. example, referring to the curves of Fig. 3 an interfering sending station might 'be located inv a direct line with the transmitting station Whose signals it is desired to receive. Assuming that the wave length of the signal transmitted from this interfering station differs from that of the desired signals for which the antenna is adjusted, the velocity of its waves on the antenna can be made to differ from their velocity in space by such an amount that a node, such as shown at points E'or G, of curve C, Fig. 3, will occur at the point where the receiving apparatusis located.

If such is the case the interfering station will produce substantially no effect upon the receiving apparatus. Under other conditions, supposing two currents in theantenna from two stations in line with each other to be represented by the curves C and H, Fig.

This permits of selectivity 3,reception could be accomplished from the station represented by the curve H by 10- cating the receiving apparatus at the point I where this current is large and the current of curve C is substantially a minimum.

If the natural capacity and inductance of the antenna have substantially the values required to give a velocity of wave propagation in the antenna equal to the velocity of light such an antenna would have the same wave velocity for all frequencies and while possessing the desired directive properties would not be selective forfrequency. Under thesecircumstances it may be desirable to insert series inductances 7, Fig. 4, which of themselves would lower the wave velocity on the antenna, and. to neutralize the effect of these inductances for a particular frequency, by inserting series condensers 8. a

. It may also be desirable in some cases in order to further sharpen the frequency selectivity of the line, to use added shunt capacity 11, as a means of slowing down the wave velocity and to neutralize this by shunt inductances 12 as indicated in Fig. 5. In this case the antenna will actpurely as a transmission line at the desired frequency while for all frequencies below that the line becomes analogous to a high pass filter or lumped artificial line consisting of series condensers and shunt 1nductances, and for all frequencies above signaling frequency the line becomes analogous in its action to a low pass filter, or lumped artificial line consisting of series inductances and shunt condensers.

. The filter action of the adjusted antenna offers a means of eliminating undesired signals or disturbances having a wave length differing from that of the desiredtsignal, This feature is under control by properly proportioning and spacing the inductances and condensers, in accordance with well established principles. An equivalent action may be obtained by using a filter in the receiving station. a

Another interesting propertyof this type of antenna is its effect in stray elimination. Consider, an antenna of this type which was ,normally slow, for example, a rubber coveredwire or iron wire, but whichis speeded up by series condensers for a particular frequency. For static impulses of steep wave front the series condensers will act prac tically as zero impedance and the static will be propagated along the ,line at its normal low velocity. Similarly, .if shunt induce tances were usedfor speeding up, these would act as infinite impedance for static impulses and the static wave would be prop agated at the low normal velocity of the line. This means that the static current in the antenna will alternately build up and then builddown by interference with the static wave in the ether and if there happens to be a certain particularly effective frequency in the static which is troublesome in exciting the receiver tuning circuit it is possible to locate the receiving apparatus at an interference node for static. The signal being a continuous wave will progressively build up 'to a large value at the points selected for the receiving apparatus.

It is not necessary for good results that an antenna of the type we have been describing be placed parallel to the direction of travel of the waves to be received, al-

though approximate parallelism may normally be desirable If the direction of travel of the waves in space makes an angle 6 with theantenna, then the point of intersection of a wave front with the antenna (i. e. the point of maximum instantaneous induced potential on the antenna) 'willmove along the antenna with a velocity cos 0 in which C is the velocity of light, and in .order for such a wave to produce the maximum effect in the receiving apparatus, the velocity of propagation on the antenna should be cos 0 there are certainvalues of the angle 6 which for any given antenna will give zero current at the receiving end. These dead points or directions from which a signal cannot be heard, depend on the wave length, the length of the antenna and the antenna wave velocity. This affords means of eliminating interference from a sending station, either by adjusting the length ofthe an tenna or by adjusting its constants and thereby its wave velocity so that signals of that wave length and coming from that directio'n-will be inaudible.

In some situations it will be 'desirable to locate the receiying station at a distance be carried to the receiving station over any good transmission circuit, but in order that this transmission circuit maynot act as a part of the antenna itwill be desirable to use a balanced, two conductor circuit, the conductors 13 being transposed at suitable intervals, as indicated in Fig. 12. -With one conductor connected to the antenna and theother grounded directly, such a circuit would not be balanced, and would act as a part of the antenna. The line may be balanced by inserting a resistance equal to the surge impedance of the antenna, in the ground connection.- Such a resistance is indicated at 5 1n Flg. 12. Another method of securing a balanced line is to use a transformer 14 between the antenna and the transmission line,

as indicated in Fig. 13. The transmission line may then be used as a separate or auxiliaryantenna, connection being made to the neutral point of the transformer'winding 15 at the receiving station. A similar connection may be made at the other end if desired. The transformer 14: at the junction may serve the useful purpose of equalizing the efl'ective surge impedances of the antenna and the transmission line, a step-up or step-down transformer being employed if these impedances differ sufficiently tocause material reflection. The adjustment of wave velocity on an antennacan be made in such away as to give not only a desired velocity for one frequency,

but at the same time to give a desired ve-' locity for a second frequency. For exam-- ple, suppose that the antenna points directly toward one'transmitting station whose signals are to be received and that a second transmitting station of greater wave length lies at an angle 0 with the direction of the receiving antenna. For signals from the first station the wave velocity on the antenna should be that of light, while for signals lf)rom the second station the velocity should cos 0 where 0 stands for the velocity of light; If an antenna is employed whose natural constants are such as to give a wave velocity C, no adjustment would be necessary for the first station but the wave velocity would be too low for best rece tion of signals from the second station. Rf now series inductances are introduced, and their reactance neutralized by series condensers for the freluency of the signals from the first station,

the wave velocity for these signals will be unchanged, but the velocity will be increased for thevlonger waves of the second station.

The larger the values of inductance and capacity the greater will be the velocity for the longer waves. Hence values of inductance and capacity can be chosen which give the desired velocity cos 0 for signals from the second station, while leaving the velocity for waves fromthe first station unchanged. k

* What we claim as new and desire to secure 'by Letters Patent of the United States, is

1. A unidirectional receiving system for radio signals comprising asubstantially horizontal directive receiving antenna which has a ground resistance at one end substantially equal to the surge impedance of said antenna.

' 2. A unidirectional receiving system for radio signals comprising a substantially horizontal directive receiving antenna which radio signals comprising a substantially horizontal directive receiving-antenna havlng a 'physical length of at least the, order of magnitude of a half wave length of the signal-- ing waves to be received, and means "at one end of said antennafor preventing the re-' flection of electric waves travelifig along said antenna.

5. A: unidirectional receiving system for radio signals comprising a substantially horizontal directive receiving antenna having a physical length of at least the order of magnitude of a half wave length of the signaling waves to be received, and means at both ends of said antenna for preventing the reflection of electric waves traveling along said antenna.

6. A unidirectional receiving system for radio signals comprising a substantially.

horizontal directive receiving antenna and a resistance having a value substantially equal to the surge impedance of said antenna connected thereto for preventing the reflection of electric waves traveling along said antenna.

7. A unidirectional receiving system for radio signals comprising a substantially horizontal directive receiving antenna and a resistance having a value substantially equal to the surge impedance of said antenna connected thereto .at one end for preventing the reflection of'electric waves traveling along ,said antenna. 1

8. A unidirectional receiving system for radio signals comprising a substantially horizontal directive receiving antenna, re-

ceiving apparatus connected thereto at the end farthest from a desired transmltting station and means at the end nearestthe desired transmitting station for preventing the reflection of electric waves traveling along said antenna. 4

9. A unidirectional receiving system for radio signals comprising a substantially horizontal directive receiving antenna, receiving apparatus connected thereto at the end farthest from a desired transmitting station and a resistance having a value sub stantially equal to the surge impedance of said antenna connected thereto at the end nearest-the desired transmitting station for preventing the reflection of electric waves traveling along said antenna.

10. A receiving system for radio signals comprising a substantially horizontal antenna having a physical length of at least the order of magnitude of ahalf wave length of the signals to be received and extending in a direction substantially par allel to the direction'of transmission of the waves to be received, ground connections at both ends of said antenna and means at the end of said antenna farthest distant from the transmitting station from which signaling waves are to be received for impressing upon receiving apparatus signaling currents received upon said antenna, the resistance of the ground connection of said antenna at the end nearest the transmitting station be ing equal to the surge impedance of said antenna.

11. A receiving system for radio signals comprising a substantially horizontal an-. tenna extending in the. genelal direction of transmission of the waves to be received, said antenna being so constructed that its natural constants are of such value that electric Waves induced therein will be prop agated along its lengthat a velocitytapproaching the velocitypf light, means for adjusting the characteristics of said antenna in such a way that electric waves of one desired frequency will be propagated therein at a predetermined velocity and electric waves of a lower frequency will be propagated therein at a. greater velocity, and means for impressing. upon the receiving apparatus signaling currents received upon said antenna, saidlast mentioned means being located at such a "oint along the length of the antenna that t e efiect upon the re ceiving apparatus of signaling currents produced by the desired waves will be comparatively large and the effect of signaling currents of a lower frequency will be a minimum.

12. A receiving system for radio signals acoaoea said antenna being so constructed that its natural constants are of such value that electric waves induced therein will be propagated along its length at a velocity approaching the velocity of light, means for adjusting the characteristics of said antenna in such a Way that electric-waves of one desired frequency will be propagated therein at a predetermined velocity and electric waves of a higher frequency will be propagated therein at a lower velocity and means for impressing upon receiving apparatus signaling currents received upon said antenna, said last mentioned means being. located at. such a point along the length of the antenna that the efiect upon the receiving apparatus of signaling currents produced by the desired waves will be comparatively large and the effect of signaling currents of a higher frequency will be a minimum.

a 13. A rceivin comprising a su stantially aperiodic horizontal receiving antenna which is so con- .structed that electric waves of difierent frequencies will be propagated along its length at different veloclties and means for impress ing upon receiving apparatus signaling currents received upon said antenna, said means being located at such a point along the length of the antenna that the efiect upon the receiving apparatus of signaling currents produced by waves of a desired frequency will be comparatively large, and

the effect of signaling currents of different frequencies will be comparatively small.

14. A horizontal antenna which is sub; stantially aperiodic for signaling waves of a desired frequency, and which has such natural constants that electric waves of all frequencies will be propagated along its length atsubstantially the velocity of light and means for adjusting the constants, of

said antenna in such a way that electricwaves of one particular frequency only will be propagated along its length at a given desired velocity and electric waves of other frequencies will be propagated along its length at difierent velocities.

15. A horizontal receiving antenna having such natural constants tliat'electric waves of all frequencies will ,be propagated along light, means for decreasing the velocity of system'for radio signals 7 wave propagation upon said. antenna and means for increasing the velocity of propagation for a particular frequency from the lowered value to a higher desired value whereby the antenna will bev rendered selective for that particular frequency.

16. A horizontal antenna having such natural constants that electric waves induced therein will be propagated along its length at a velocity approaching the velocity of light, and means for ad usting the characteristics of said antenna in such a way that electric waves of one desired frequency will be propagated therein at a predetermined velocity and that electric waves of a lower frequency will be propagated therein at a greater velocity.

17. A substantially horizontal antenna having such natural constants that electric Waves induced therein will be propagated along its length at a velocity approaching the velocity of light, and means for adjusting the characteristics of said antenna in such a way that electric waves of one desired frequency will be propagated therein at a predetermined velocity and electric waves of a higher frequency will be propagated therein at a lower velocity.

18. A substantially horizontal antenna which is so constructed that electric waves will be propagated therein at a velocity substantially equal to the velocity of light and means for adjusting the constants of said antenna in such a way that continuous signaling electric waves of substantially sine wave form and of a desired frequency will be propagated therein at a velocity difierent from that of transient electric waves having a steep wave front.

19. A receiving system for radio signals comprising a, horizontal receiving antenna having such natural constants that electric waves will be propagated therein at velocity substantially equal to that of light, means for adjusting the constants of said antenna insuch a way that signaling current waves of substantially sine wave form and of a desired frequency will be propagated therein at a velocity diflerent from that of transient electric waves having a steep wave front, and receiving apparatus connectedto said antenna at a point where electric waves of steep wave front induced in the antenna length at a velocity approaching the velocity induced therein will be propagated along its of light, means for adjusting the charac- 9 teristics of said antenna in such a way that electric Waves differing in frequency will be propagated therein at different velocities, said antenna being of such length that at a chosen point thereon waves of one frequency will have a large value and waves of another frequency will be substantially of zero value.

21l A receiving system for radio signals comprising a substantially horizontal an,- tenna, said antenna. being so constructed and adjusted that electric waves of a desired frequency will be propagated therein at a predetermined velocity,'said antenna being of such length that at a chosen point therein electric waves produced by signals coming from a desired vdirection will be of large value and electric waves produced by signaling waves coming from a different direction will be of substantially zero value.

22. A horizontal receiving antenna which is so constructed and adjusted that current waves induced therein by signaling waves coming from different directions will be propagated therein at different velocities with respect to the velocities of the corresponding signaling waves in the ether and that at a chosen point therein electric waves produced by signaling waves coming from a desired direction will be of large value and CHESTER w. RICE. EDWARD w. KELLOGG.

electric waves produced by signaling waves 8

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