Патент USA US2408118код для вставки
Sept, 24, 1946. w. H. WIRKLER 2,408,]; 18 AZIMUTH RADIO DIRECTION FINDING SYSTEM Filed Feb. v14, 1959 2 Sheets-Sheet l ' INVENTOR. ' wa?’w 3% QWMKKQ/U, BY 6. ATTORNEY . ' Sept. :24, 1946., w. H. WIRKLER ’ 2,408,118 AZIMUTH RADIO DIRECTION FINDING SYSTEM Filed Feb. 14, 1939 2 Sheets-Sheet, 2 #ETFRODYA/E OSC/Zl A701? IN VEN TOR. WW4? ael Wm‘J BY ' é. ATTORNEY . Patented Sept. 24, 1946 \ UNITED 2,408,118‘ STATES PATENT OFFICE ‘ 2,408,118 AZIMUTH RADIO DIRECTION FINDING SYSTEM, Walter H. Wirkler, Cedar Rapids, Iowa, assignor to Collins Radio Company, Cedar Rapids, Iowa, a corporation of Iowa - Application February 14, 1939, Serial No. 256,339 16 Claims. 1 My invention relates broadly to direction ?nd ing systems and more particularly to a circuit arrangement for an azimuth direction ?nding system whereby the direction of arrival of a radio signal may be visually observed on a suitably calibrated scale. One of the objects of my invention is to provide a circuit arrangement for accurately indicating the direction of arrival of a radio signal from a mobile body carrying a radio transmitter at a ?xed position whereby the direction of the mobile body may be readily determined from the ?xed position. (Cl. 250-11) ' 2 trating the manner of exciting the injector an tenna of the multiple antenna system employed in the system of my invention and illustrating the manner of controlling the amount of high fre quency energy supplied to the injector antenna under control of one of the'signal receiving cir cuits connected to one of the coacting receiving antennas; and Fig. 3 is a vector diagram explain-V ing the manner of operation of the system of my 10 invention. Direction ?nder systems have heretofore been, known in which the circuit balance is obtained wholly in the antenna circuit. This applies to the many variations of the so-called Adcock sys Another object of my invention is to provide a circuit arrangement for a radio receiving system 15 tem and equally to the systems using direction having means for providing an instant indication ?nding loops. In the system of ‘my invention, of ‘the direction of arrival of a radio signal. electrical balance of the antenna circuits ‘is not Still another object of my invention is to pro vide a circuit arrangement for a signal receiving essential and is not obtained by means ,within the antenna circuit per se. ' ' system in which separate receiving antennas are 20 I provide an arrangement of antennas in geo located in spaced relation in positions constituting graphically spaced positions' at the apices of an the apices of an equilateral triangle with separate equilateral triangle connected through separate receiving circuits connected with the antennas receiving circuits to a' polyphase transformer and with the indicating apparatus, and in which system from each phase of which energy is ap-' an injector antenna and associated oscillator are 25 plied to the actuating magnet of an electromag arranged at the center of the equilateral tri netically operated integrating calibrated instru angle for electromagnetic coaction through space ment. The calibrated instrument is arranged to with the antennas leading to the receiving circuits directly indicate the direction of arrival of a. radio and to the indicating system. _ signal source with respect to the geographically A further object of my invention is to provide 30 spaced antennas. An injector antenna is located an indicating system for determining the direc centrally of the equilateral triangle formed'by tion of arrival of a radio signal in which inde the several receiving antennas and is supplied pendent antennas are located in geographically by a radio frequency source, the amplitude of spaced positions constituting the apices of an which is controlled by a portion of the energy equilateral triangle and connected through sepa 35 received by one of the receiving circuits asso-' rate receiving circuits with an indicating system ciated with the several antennas. The injector‘ and adapted to electromagnetically coact with antenna electromagnetically coacts with the re an injector antenna centrally positioned within ceiving antennas through space in delivering a the equilateral triangle and excited from a regu radio frequency current to the several receiving lated source of radio frequency energy which is 40 circuits. The operation of the indicator is very controllable automatically from one of the receiv accurate and permits the use of the system at ing circuits electrically connected with the indi ground stations for directly observing the direc cating system. ' tion of aircraft from the station, or the direction A still further object of my invention is to pro ?nder system of my invention may be used on vide a circuit arrangement for integrating in a 45 mobile bodies such as ships or-aircraft for directly calibrated indicating system the effects of a re indicating the direction of a radio transmitter mote signal source upon a multiplicity of pre for facilitating the navigation of the mobile body arranged antenna systems for accurately indi toward. the emitting source. cating the direction of movement of a signal The circuit arrangement of the receiving sys source toward the antenna systems. 50 tem is given diagrammatically in Fig. 1. Three Other and further objects of my invention re conventional receivers are individually connected side in the circuit arrangement for a direction through transmission lines to three separate an ?nder system as set forth more fully in the speci tennas represented at l, 2 and 3. The anten ?cation hereinafter following by reference to the nas themselves are arranged at the vertices of accompanying drawings, in which: 55 a triangle where the distance between the an Figure 1 diagrammatically shows the direction tennas is not greater than 1./2A of the received ?nder system of my invention and schematically wave. A fourth antenna or “injector antenna” illustrates the indicator system which directly indicated at 4, is located at the center of the indicates vthe direction of approach of a radio equilateral triangle outlined by the three an signal source; Fig. 2 is a diagrammatic view illus 60 tennas I, 2 and 3 referred to hereinbefore. The, 2,408,118 4 3 from receiver 2’. The voltage between ground and tap 'lc on the primary winding 1 connected fourth‘ antenna 4 is connected to the output of a heterodyne. oscillator 5, the purpose of which to receivers I’ and 2' is the average or half the is to produce a low frequency audio beat note in vector sum of the two voltages from receivers the output of each of the three receivers l’, 2', l-’ and 2', and is represented in Fig. 3 by vector and 3’. The phase relation between the three a BA which is one-half the vector sum 0A’ of the audio frequencies produced at the receiver ter voltages represented by vectors il—l” and Ei—2". minals and the phase relation of the three re The voltage across the terminals of primary ceived signal voltages in the antennas may be winding ‘I is the vector difference of the voltages shown to be identical. From the phase relation of the three low frequency voltages, it may furv 10 Evenv and. E2~_o from the receivers I’ and 2’, respectively, and is represented by vector 0B in ther be shown that the direction of signal arrival Fig. 3, wherefrom it is seen that the average volt can be determined. age QA and the difference voltage EB are in phase The indicator is of the “Selsyn” type and is principally actuated by the difference between quadrature. Windings ‘l’, 8' and 9’, Fig. 1, are the sec the voltages in receivers‘ I’ and 2', 2’ and 3', and 15 ondary windings respectively of primaries v1, 3 3’ and I", in paired combinations. It may be ob and 9 and are coupled therewith. -The voltage served at this point that insofar‘ as the operation across primary winding ‘I, for example, is applied of the three receivers is concerned, it is strictly through secondary 1’ in push-pull relation to and‘ entirely conventional. They may be of a type employing automatic volume control, and 20 diodes V2 and V3, and the other primary voltages are similarly applied in the respective circuits. their audio gain controls so adjusted to produce Diodes V2 and V3 serve as independent recti?ers equal magnitude output voltages. My invention feeding the output resistor R4, the center tap is directed to the utilization of "the three audio E2 of which is grounded at M. A coupling trans~ voltages to operate a directional indicating sys former T1 is connected in the anode circuit of tem shown generally at 6 and resides in an ar tube V1 with its secondary connected between rangement of injector antenna to produce a low ground and the center tap It! on secondary wind frequency beat note in the output of each of the ing 1’. Recti?ers V2 and V3 are thus energized three receivers where the phase relations of the by the difference voltage, represented by vector three low frequency voltages are identical to the phase relations of the three high frequency volt so BB in Fig. 3, in push-pull relation, and by the average voltage, represented by vector 0A in ages induced in the separate antennas by the VFig. 3, in balanced relation, being applied be distant transmitter. l”’-—0, 2”--B and 3"-€! are tween taps ii] and I2. The resulting voltage the terminals of the radio receivers arranged across output resistor R4, due to interaction of Y connection. Reference‘ characters 7, 8 and 9 the diiference and average voltages, is applied to designate transformer primaries arranged in del winding W1 of the indicator device 6. ta. The ?rst receiver voltage is designated Referring again to Fig. 3, it was noted above Ew-‘o, the voltage of the second receiver E2"-0 that the diiierence voltage, vector BB, and the and the third receiver voltage E3"_o. These three average voltage, vector BA, are in phase quadra voltages are low frequency voltages of the same magnitude and frequency but different phase. 401 ture at the terminals and center~tap of primary winding ‘J. In order that these voltages may The magnitude of the voltages may either be ad coact properly in the circuits of recti?ers V2 and justed manually or automatically, preferably the V3, however, they must be substantially in phase. latter. The voltage impressed across the primary The purpose of the resistor R1, condenser 01 and terminals of the transformer primary Tis the tube V1, connected between the center taps To di?erence between the voltages Ew-o and Ez'l-o. and I ll on the primary ‘I and secondary ‘I’, re This voltage will be designated spectively, is to apply a phase shift of essentially 90° to the average voltage, represented in Fig. 3 by: vector 0A, to bring the average voltage into Similarly, the voltage‘ across the primary wind ing 8 is E1"_3"—V~=E1"_o—Es"-o; and the voltage 50 phase with the difference voltage. In Fig. 3, the phase shift is indicated by the rotation of across the primary Winding'B; is vectors‘ 0A and BA’ to the positions BArand 0A1’ in‘ coincidence with the difference voltage vector BB. Voltages represented by vectors 9B and 0A1 These voltage differences are impressed across are; therefore, the voltages effective in the recti the primaries‘ ‘I, 8" and 9 simultaneously. ?ers V2 and V3. Terminal 1c is a center‘ tap on transformer From Fig. 3, it will also be seen that if the primary 1.‘ and the voltage between To and ground relative phase of vectors 0-!" and 0‘—2" is will be the average of the voltages Ei"_o and‘ reversed, the difference voltage vector BB will be E2~_o; Similar center taps on the windings 8 and 9 shown at so and 90 which give the aver 60 reversed to position 3B1 while the average volt~ age vector 0A1 will remain as before. The result ages of the: voltages E2”-—U and E3"—0; and E3"—o in the output resistor R4 is a reversal in polarity and El”-0. The center tap 10 on winding ‘1 is of the direct voltage produced by the coaction of connected to the grid of a vacuum tube V1‘ the difference and the average voltages in the through a resistance R1. Placed effectively in recti?ers, which eliminates 180°’ ambiguity in the parallel with the grid'is- a condenser C1 which indication. The knowledge that one of the re has a small‘ reactance in comparison with the sultant vectors does‘ not change phase with re value of the resistance R1. Condenser C2 and versal of the relative phase of the component resistance R2 as well as C3 and R2 comprise con vectors provides the factor by which the relative ventional means of obtaining bias voltage for phase is determined to avoid the 180° ambiguity. tube V1 while source B represents the conven t will be understood that either the difference tional means for securing plate potential for voltage or the average voltage may be subjected to the phase shift to make the voltages in phase Referring to the‘vector diagram, Fig. 3, the preparatory to coaction' in the recti?ers V2 and vector G—_l’“ represents the voltage. Eweofrom receiver l?and vector IJ—2” the voltage Ea"-t _ V3‘. And, likewise,‘ it will be understood that the tube‘vi. ' ’ 2,408,118 5 difference voltage may be applied'in balanced relation to the diodes V2 and V3, and the average voltage in push-pull relation, if desired, instead 6 pie, north. The position of the indicator I6 is then taken as north, and if a compass type dial is used on the indicator, the equipment when tuned to a signal the direction of-arrival of which In the event the voltages represented at 0-4" is unknown, will position the indicator l6’ and and 0-2", Fig. 3, are in phase and equal in mag show the direction of arrival of the incoming nitude, the difference voltage represented by vec wave. The windings W1, W2 and W3 of the ‘indie tor 03 will be zero. In Fig. 1, then, no voltage cator are so electrically oriented that they pro will exist across transformer primary 1 but an duce magnetic ?elds 120° apart, so that the indi average voltage 0A, Fig. 3, will exist between tap 10 cation of the “permanent magnet rotor, I5 is in 1c and ground. This voltage will be shifted in accord with the direction of any incoming signal phase, ampli?ed by tube V1 and operate recti?ers which may be received. . or diodes V2 and V3 identically. Equal and oppo As heretofore explained, the system in its pre site currents will therefore flow in the two halves ferred arrangement employs three substantially of resistor R4 and hence no voltage will exist 15 identical receivers and a heterodyne oscillator across the terminals of R4. The currents pro arranged for single dial control. The frequency duced in R4, however, have a ?xed directional of the heterodyne oscillator should preferably be factor which is maintained regardless of the rel kept within 50 to 150 cycles of the received signal ative phase relations of the components El"~—0 frequency. This is readily accomplished by of in the relation shown and described. ' and E2"—o, and thus these currents provide a 20 means of an acceptable automatic frequency con reference sense in the control of the indicator trol system. It is further desirable thatthe radio 6 through winding W1. If the voltages E’i"__o and frequency output of- the heterodyne oscillator and E2"-o are slightly displaced in phase with re hence the injector antenna power input be read spect to each other, as represented in Fig. 3, a ily controllable. . ' . voltage will exist across transformer secondary Fig. 2 shows one arrangement of anlautomatic ‘l’ which will increase the voltage delivered output control for the heterodyne oscillator 5 through center tap ID on one diode and decrease which connects to the injector antenna 4. A por it on the other. Under these conditions the cur tion of the output power of one of the receivers rent in the two halves of R4 will be unequal and I’, 2’ or 3' is recti?ed and suitably ?ltered for the difference current which will flow through use as a direct current control voltage. If the the winding W1 of the indicating instrument 6 audio frequency output of the receiver is too low, will be proportional to the magnitude of the dif the magnitude of the current in the injector an ference of the voltages El"—0 and E2"-o. It tenna 4 must be reduced. 'This lack of D. C. con should ‘be observed at this point that if the trol voltage therefore is utilized to increase the above discussion applies when.E1~_o leads E2"-o bias voltage on the electron tube ampli?ers V7 in phase value, a current-will flow in the winding and V8. The increased bias on these tubes will W1 in a direction, for example, indicated by the reduce the input to the injector antenna 4, allow arrow. If the phase relations of Ew-n ' and the automatic volume controls of thereceivers to E2"-o are reversed so that the voltage E2"—0 leads operate and increase the gain of the receivers and El"—0 the current in the winding W1 of the indi thus raise the audio frequency output of the re cating instrument 6 will be reversed. An exactly similar circuit arrangement, which If on the other hand the audio frequency volt I have indicated by ‘similar reference characters age is too high, the direct current control voltage with primed designations, is used to supply the will also be high. This will reduce the bias on winding W2 of'the indicating instrument 6 in vacuum tubes V7 and Va'resulting in an increase accordance with the voltage di?erence E1"—-0 and in injector antenna input. This increase in in~ E3"—D. A third circuit arrangement represented iector antenna input will operate the automaticv by elements of identical nature designated by volume controls of the receivers I’, 2' and 3', so double primed characters supplies a winding We as to reduce their gain and hence reduce ‘the of the indicating instrument 6 in accordance magnitude of the audio frequency output voltage. with the voltage difference Es'l-o and Ezlf-o. In Preferably the relative magnitude of the injector each instance the secondary windings for the voltage’ and the received signal voltage in- any delta connected primary windings have been receiving channel should be of the order of 10:1. shown diagrammatically spaced from the coact When the ratio is of‘ this magnitude or'greater,‘ ceivers. ' ' ing primary windings, but it will be understood , the audio frequency output of each of the re'-' that the windings are inductively coupled in each ceivers will be substantially sinusoidal. ‘ I have instance, that is to say, winding 1' couples with shown the output of receiver I’ from terminals winding 1; winding 8' couples with winding 8; l"—0 leading to primary winding 1 of the delta and winding 9' couples with winding 9, as indi connected transformer, but, with leads I8 ex cated in Fig. 1. 60 tending therefrom to transformer 19, the output The system of my invention develops three of which connects to the full wave recti?er cir independent currents. The magnitude of each current is proportional to the vector di?erence between the audio voltages from two of the three receivers. The direction of the current ?owing in any winding W1, W2 or W3 of the indicator 5 is determined by which of the two voltages in volved in the subtraction is the leading voltage. These currents act on the magnetic member l5v for controlling the position of indicator I6 with respect to av calibrated dia1 indicated generally at I‘! for readily determining geographical loca tions. - The system can readily be calibrated by receiv ingla signal from a known, direction, for exam cuit shown at 20 for developing a control voltage across resistor 2|. The" resistor 2| connects through resistances 22 and 23 with the control grids of ampli?ers V7 ‘and ‘V8, respectively, for controlling the operation of the'tubes as ampli ?ers and the magnitude of the current impressed upon the injector antenna 4. I have shown am pli?ers V7 and V3 connected in conventional man ner through tuned circuits 24 and 25 to the in jector antenna 4. - ~ While I have described my invention in certain of its preferred embodiments, I desire that it be understood that modifications may be made and that no limitations upon my invention arcin 2,408,118; 7 of‘theappendedclaims.v . . i ~ rality of stationary‘geographically spaced receiv ' ing antennae, an‘. injector antenna centrally dis posed with respect vto said receiving antennae‘, What I claim as new and desireto secure by Letters. Patent of the United States is as fol lows: ‘ 8 ‘ 5. Aidi'rection1?ndingjsystem;comprisinganplu tended; other than may belimpcsedby, the: scope means for electrically exciting-said: injector an tenna, separate receiving circuits: individual" to ' I. iAdirection?nding system comprising a- plu said receiving antennae, a-polyphase‘circuitv have ing the respective terminals, thereof connected with the individual receiving circuits, an ‘electri posed with respect to said receiving antennae, means for electrically exciting said injector an 10 cal indicator, magnetic meansv disposed in'spaced tennaifor impressing heterodyning energy upon ~ positions about‘ said electricalv indicator fOI‘I'COIl trolling said indicator ‘in. accordance; with: the‘ said plurality of geographically spaced receiving rality ofstationary geographically spaced receiv ing antennae, an injector: antenna centrally dis energy received by the respective’ receiving an~ antennae, independent receiving: circuits con tennae,. circuits coupling‘the last said means-with nected with said‘ plurality of geographically respective phases of said.‘ polyphase- circuit; spaced; receiving antennae, a polyphase circuit 15 the and meansinterconnecting the (rutput: of one- of interconnected, with the: outputs of said: inde said receiving circuits’ with the; means for elec pendent receiving circuits, an angularly shiftable trically exciting said injector antenna .for'con indicator, and means for'm'agnetically controlling trolling the energy impressed by said. injector said ‘indicator connected with said. polyphase. cir cuit' whereby‘ said. indicator may be moved to a .20 antenna upon each ‘of’ said geographicallyspaced receiving‘. antennae. ' position corresponding to theposition of a- radio 6; A ‘direction ?ndingsystem’ comprising. av plu transmitting‘ source with respect to said station rality of stationary geographically spacedreceiv ary‘ geographically spaced receiving antennae. ing antennae, an‘ injector-antenna centrally dis posed with‘ respect to said receiving. antennae, 25 means for electrically exciting‘s‘ai‘d? injector. an i'ngi antennae, an injector antenna centrally dis tenna, separate receiving‘ circuits individual ‘to posed" with respect'to said receiving antennae, said receiving‘antennae, a polypha'se circuit hav means. for electrically exciting said injector an 2. A direction ?nding system comprising a plu rality‘ of stationary geographically spaced'receiv tenna, independent‘ receiving circuits connected with said spaced. receiving‘ antennae, a multi ing‘ the respective terminals‘v thereof connected 30 with. the individual receiving" circuits, .anx electri phase'circuit' interconnected with the outputs of said receiving circuits, an angularly shiftable in dicator; having magnetic. control means therefor, and circuits coupling said-magnetic control means with‘ said multiphase circuit wherebysaid angu 35 larly sliiftable indicator is moved to a position indicating‘the'position of a radio signalling source with respect to said’ plurality of stationary geo graphically spaced receiving antennae. ‘ 3. A direction ?nding system comprising a plu rality of ?xed geographically spaced receiving antennae, an injector antenna centrally disposed with, respect to said receiving. antennae, means for electrically exciting said injector antenna, separate receiving circuits individual to. said re cal’ indicator,‘ rneaz'isv for magnetically actuating said electrical indicator; circuits couplingv the last said means with theirespective phases of said pclyphase circuit, and re'cti?enmeans. disposed in each. of said coupling circuits for impressing recti?ed energy'upon‘ the means for. magnetically actuating saidv electrical indicator.‘ ' 7.‘ A-direction ?nding‘ system comprising a plu rality of stationary geographically spacedireceiv ing antennaean injector‘ antenna centrally dis ' posed with respect'to said receiving. antennae, means for? electricallyv exciting said 'in‘jector' an tenna, separate receiving circuits individual to said receiving antennae, a polyphase circuit hav ing the respective: terminals thereof connected with the individual.‘ receiving circuits, an electri cal indicator; means for magnetically actuating the last said electrical indicator; circuits coupling individual receiving circuits, an electrical indi- V 'said meansv with the respective phases of said cator, means for magnetically actuating said electrical indicator, andcircuits coupling the last 50 polyphase circuit, a full wave recti?er circuit dis posed in each‘ of said‘ coupling circuits for im said means with the respective phases of said pressing recti?ed energy of both half waves‘ in polyphase circuit, the. means for magnetically ‘ac opposite relation. upon the means for magneti tuating said. indicator being disposed in syms cally’ actuating said electrical indicator, and metrically spaced relation in a manner propor means connected between the respective phases tional to the ?xed geographical separation of said of said polypha'se'circuit and each of said recti?er ceiving antennae, apolyphase circuit having the respective terminals thereof connected with‘ the receiving antennae. ' . 4. A direction ?nding system comprising a plu rality of fixed‘ geographically spaced receiving antennae, an‘ injector antenna- centrally disposed with respect to said receiving antennae, means for" electrically‘ exciting said injector antenna, separate receiving» circuits individual to said re ceiving antennae, a polyphase circuit‘ having the respective terminals thereof connected with the individual. receiving circuits, an electrical indica tor, means formagnetically' actuating said elec trical indicator, said last mentioned means being disposed in spaced relation about said electrical circuits for counteracting‘ the recti?ed. current of one half Wave in each of said coupling circuits. '8. A direction ?nding system comprising a plu rality of stationary geographically spaced'receiv ing antennae, an injector antenna centrally dis posed with respect to said receiving antennae, means for electrically exciting said‘ injector an tenna, separate receiving circuits individual to said receiving antennae, a polyphase circuit hav ing the respective terminals thereof connected with the individual receiving circuits, an electri cal indicator, and magnetic means corresponding in‘ number to the number of said geographically indicator‘in. positions proportionalto the relative positions’ of said ?xed geographically‘ spaced re 70 spaced receiving antennae, one of said magnetic means being individual to each of the‘ phases of ceiving antennae, circuits coupling said last'meng said polypha'se circuit, whereby the e?ects of tioned‘mea'ns with the respective phases of said each of said magnetic means may be integrated polyphase circuit, and means for independently with respect to said electrical indicator for shifts controlling the'phase ofxthe currents inrea‘ch of in'g said; electrical- indicator to a position which said last'mentioned-circui'ts. " ~' i 2,408,118 9 10 corresponds to the position of a radio signalling source with respect to the plurality of geographi cally spaced receiving antennae. 9. A direction ?nding system comprising a plu rality of geographically spaced receiving an tennae, an injector antenna centrally disposed With respect to said receiving antennae, means for electrically exciting said injector antenna, said polyphase circuit whereby said magnetic de vices conjointly control the angular movement ' of said electrical indicator in response to signal ling energy incident upon said plurality of re ceiving antennae from a signalling source for indicating the position of the signalling source with respect to said receiving antennae. 13. A direction ?nding system as set forth in claim 3 and including independent circuits con separate receiving circuits individual to said re ceiving antennae, a polyphase circuit having the 10 nected in balanced relation between the phases of said polyphase circuit and said coupling cir respective terminals thereof connected with the cuits for producing equal and opposite currents individual receiving circuits, an electrical indi in each of said coupling circuits in predetermined cator, means individual to each of the phases of relation to the operating characteristics of said the polyphase circuit for electrically controlling the movement of said electrical indicator, and 15 indicator, for establishing a phase reference in each of said coupling circuits for the currents means electrically connected with the output of impressed on said indicator actuating means, said one of said receiving circuits and with said means impressed currents having a direction through for electrically exciting said injector antenna for said actuating means determined by whichever controlling the amplitude of the energy impressed by said injector antenna upon the plurality of 20 of the opposed currents is in phase therewith. geographically spaced receiving antennae. 10. A direction ?nding system comprising a plurality of geographically spaced receiving an tennae, an injector antenna centrally disposed with respect to said receiving antennae, means 25 for electrically exciting said injector antenna, separate receiving circuits individual to said re ceiving antennae, a polyphase circuit having the respective terminals thereof connected with the individual receiving circuits, an electrical indi cator, means individual to each of the phases of the polyphase circuit for electrically controlling the movement of said electrical'indicator, and 14. A direction ?nding system as set forth in claim 4, with said means for independently con trolling the phase of the currents in each of the coupling circuits including midtap connections in the respective phases of said polyphase circuits and in the coupling circuits related thereto, and independent circuits including phase shifting means connected between corresponding mid-tap connections for producing equal and opposite currents in each of said coupling circuits in phase and in phase opposition with respect to the cur rents impressed on said indicator actuating means and in predetermined relation to the op erating characteristics of said indicator, for means including a recti?er circuit electrically connected with the output of one of said receiv 35 establishing a phase reference in each of said coupling circuits for the currents impressed on ing circuits and with said means for electrically exciting said injector antenna for controlling the said indicator actuating means, said impressed currents having a direction through said actuat ing means determined .by whichever of the op cally spaced receiving antennae. 40 posed currents is in phase therewith. 15. A direction ?nding system comprising a 11. A direction ?nding system comprising a amplitude of the energy impressed by said in jector antenna upon the plurality of geographi plurality of geographically spaced receiving an plurality of equally spaced receiving antennae, an injector antenna centrally disposed with re tennae, an injector antenna centrally disposed spect to said receiving antennae, means for elec with respect to said receiving antennae, means for electrically exciting said injector antenna, 45 trically exciting said injector antenna with heterodyning energy, separate receiving circuits separate receiving circuits individual to said re individually connected to said receiving antennae, ceiving antennae, a polyphase circuit having the a corresponding number of recti?er means, respective terminals thereof connected with the means for interconnecting said recti?er means individual receiving circuits, an electrical indica tor, means individual to each of the phases of 50 and said receiving circuits with each said recti?er means energized in balanced and unbalanced re the polyphase circuit for electrically controlling lation by the vector sum and the vector di?er the movement of said electrical indicator, and ence of the heterodyne output voltages of two means including a. full wave recti?er circuit elec receiving circuits connected with adjacent an trically connected with the output of one of said receiving circuits and with said means for elec 55 tennae, phase shifting means for reconciling the phases of the vector sum and difference voltages trically exciting said injector antenna for con for operation with respect to the recti?er means, trolling the amplitude of the energy impressed and an electromagnetic indicator having ?eld by said injector antenna upon the plurality of windings spaced in accordance with the spacing geographically spaced receiving antennae. 12. A direction ?nding system comprising a 60 of said receiving antennae and individually ener gized from said recti?er means. ' trio of geographically spaced receiving antennae 16. A direction ?nding system as set forth in arranged at the apexes of an equilateral triangle, claim 15 wherein the vector sum voltages are an injector antenna centrally disposed with re shifted in phase by 90° and applied to the recti spect to said receiving antennae, means for elec trically exciting said injector antenna, a receiv 65 ?er means in balanced relation and the vector difference voltages are applied to said recti?er ing circuit individual to each of said receiving means in unbalanced relation, the vector differ antennae, a three-phase delta-connected circuit ence voltage undergoing phase reversal and the having the respective terminals thereof connected direct output voltage of the recti?er means being with the individual receiving circuits, an electri cal indicator, a plurality of magnetic devices as 70 reversed in polarity with reversal of the relative phase of the component heterodyne voltages in sociated with said electrical indicator spaced sub any instance, whereby 180° ambiguity in the in stantially 120° about said electrical indicator, dication is avoided. and separate circuits interconnecting the said magnetic devices with the respective phases of WALTER H. WIRKLER.