US2251708A

US2251708A - Direction finder antenna system

Info

Publication number: US2251708A
Application number: US139143A
Authority: US
Inventors: Edward J Hefele
Original assignee: Individual
Current assignee: Individual
Priority date: 1937-04-27
Filing date: 1937-04-27
Publication date: 1941-08-05
Anticipated expiration: 1958-08-05

Description

Aug. 5, 1941.

E. ,1. HEFELE DIRECTION FINDER ANTENNA SYSTEM Filed April 27, 1937 4 Sheets-Sheet 1 R. F. AMPLIFIER AMPLIFIER .9 INVENTOIL durnrdg. ffil d ATTORNEY.

-o RECEIVER Aug. 5, 1941. E. J. HEFELE 2,251,708

DIRECTION FINDER ANTENNA SYSTEM Filed April 27, 1937 4 sheets-sheet 2 l l ea RADIO RECEIVER 9 50 sz lmmJ ez g i 56 W60 [57 51 7 6 I,

rug-' 6 k I z I 60 57 i 51 e 6 6 1 65 l {19 ,8 RADIO I l RECEIER 50 mill i 56 W rigu & i I

50 /9 55 3 1 TIME 57 9 DELAY NETWORK Fig-12 i T RADIO 5 RQECEHgER 55 [maul i 61 54 5g; OHM

NETWORK 1629114 'n DELAY NTWOK Aug. 5, 1941. .E. J. HEFELE ,7

DIRECTION FINDER ANTENNA SYSTEM Filed April 27, 1957 4 Sheets-Sheet s nu. no) ulnnuunn u-mun nnnuuuno Figfls Fig-'19 Fig: 20 Fig: 21

ATTORNEY.

1941- E. J. H EFELE I 2,251,708

DIRECTION FINDER ANTENNA SYSTEM Filed April 27, 1937 4 Sheets-.-Sheet 4 RADIO RECEIVEP O I .107 65 113 4 J i v 0 1; 0"" 'T RZ Z E ER 'NPUT 711 112 i I "I 6 109 L 'R l n m 1- 1 3 AUDIO FREQUENCY 5i OSCILLATOR INV EN TOR. durarwl3.9(e'fele ATTORNEY.

Patented Aug. 5, i941 {UNITE s'm'res PATENT, OFFlQE.

2,251,708 DIRECTION FINDER ANTENNA SYSTEM Edward J. Hefcle, Amityville, N. Y. Application April 27, 1937, Serial No. 139,143

16 Claims.

This invention relates to direction flnders and more particularly relates to antenna systems for right-left indicating direction finder systems.

Automatic right-left indicator systems, particularly for aircraft, have heretofore generally depended upon the formation of cardioid reception patterns and used a loop antenna combined with a vertical or non-directional antenna in a predetermined relation. The resultant cardloid patterns depended upon critical tuning andelectrical phasing of the loop antenna system.

Changes in temperature of the loop antenna and slight variations in tuning caused serious misphasing at the antenna stage of the radio receiver and resulted in reception patterns producing null or zero intensity on bearings actually many degrees off-course. Such directional errors are very serious, particularly on aircraft where radio directional guidance is often. the sole navigational aid.

In accordance with my present invention, I contemplate producing cardloid reception patterns by means of vertical antenna arrays combined at the antenna input stage in a predetermined manner. The cardioid patterns of my invention are not dependent upon tuning or critical variable electrical conditions but remain constant after installation for all reception pur- I utilize the vertical antenna array to reception patterns for controlling-the deflections of a. right and left indicator.

Vertical mast antenna, even when streamlined, produces an aerodynamic resistance or drag to flight of approximately six pounds at a flight speed of 200 miles per hour. Accordingly, it is greatly advantageous to minimize the number of mast antennae arrays necessary for accurate directional guidance. invention, two, three or four vertical antennae may be used for such a right-left indicator.

An aircraft traveling at high speed through the atmosphere often passes through rain, dust, snow and fog, the particles of which impinge at high velocityupon the antenna structure and set up .static impulses which are transmittedv through. to the radio receiver. Such static often seriously impairs reception. Loop antennae have been successfully shielded by enclosing them in a. metallic housing, which housing is placed at grounded potential at its nodal point. In accordance with my invention, I provide a. metallic shield surrounding the mast antenna and connect the shield to ground potential through a radio frequency choke coil. In this manner, the

In accordance with myenclosed mast antenna.

charges produced by the impinging high velocity particles are dissipated by conduction to ground through the high impedance choke coil and the radio signals areonly somewhat reduced in intensity as they pass through the shield to the By maintaining the shield at a high radio frequency impedance, the sensitivity of reception by my novel shielded mast antenna is substantially maintained. preferred construction for an anti-static antenna is the use of a doublet or opposed mast antenna array, each mast being surrounded by a spaced shield connected to ground by an individual choke coil. All electrical impulses and transients are conducted to ground free of any part of the radio circuit.

Accordingly, it is an object of my present invention to provide a novel method of and means .for producing directional reception patterns with independent of tuning or electrically varying conditions.

A further object of my present invention is to provide a novel anti-static vertical antenna system.

These and other objects of my present invention will become apparent in the following description of the invention taken in connection with the drawings, in which:

Figures 1 and 1A are schematic showings of preferred non-directional antennae enclosed by streamlined shields for eliminating static electrical pulses encountered in high speed flight.

Figure 2 is an enlarged cross-sectional view taken along 2 through the anti static mast antenna of Figure 1.

Figure 3 is a fragmentary elevational view of a modified shield for the anti-static mast antenna of my present invention.

Figure 4 is across-sectional view taken along 4-4 of Figure 3.

Figure 5 is a schematic electrical diagram of a right-left indicator operating with a double' sponding to Figure 5 and employing balanced doublet antenna arrays.

Figure 17 is a polar diagram of the right and left cardioid reception patterns produced by the antenna system of Fig. 16. v

Figures 18 to 22 illustrate different forms of radio 'c uency time-delay networks which may be employed in carrying out certain modifications of my present invention.

Figures 23 is a schematic diagram corresponding to Figures 5 and 16 showing a preferred timedelay network in circuit with the antenna system.

Figure 24 is a schematic electrical diagram of a cardioid pattern right-left indicator in accordance with my present invention employing ical antenna arrays using mechanical e 25 is a schematic electrical diagram of pattern rightleft indicator in acith my present invention employing tical antenna arrays using mechanical Figure 26 is a schematic electrical diagram of a right-left indicator corresponding to Figure 25 but employing electronic switching means at the antenna input and indicator.

In Figure 1 I have shown in elevation a preferred arrangement for shielding the vertical antenna from the effects of static produced by high velocity particles encountered in high speed night through fog, dust and storms. The vertical or mast antenna array 30 is supported upon the exterior surface 3! of a vehicle such as a ship, car or aircraft. Figure 2' is a cross-section taken along 2--2 of Figure 1 and drawn to a larger scale. anti-static shielding as applied to a vertical mast antenna, it is to be understood that it may similarly be applied to the top and bottom rods of a doublet antenna array as well as to an antenna wire supported in any other angular relation with respectto the surface of the vehicle.

Although I prefer to illustrate the In my co-pending application Serial No. 139,142

filed April 27, 1937, I illustrate atrailing wire antenna of an aircraft statically shielded by the principle herein described for the vertical mast.

The vertical antenna array .30 comprises a central conductor rod 32 which is the antenna wire for the radio receiver. Surrounding the antenna wire 32 is a metallic shield 33 preferably shaped in a tear-drop or stream line form having a minimum aerodynamic resistance in the direction of flight of the aircraft. Accordingly, the leading edge 34 ofthe shield 33 is wide and rounded and the trailingedge 35 is narrow and pointed. I prefer to incorporate a solid insulation material 36 between the conductor 34 and the metallic shield33 and employ the insulation 36 to rigidly support the relatively thin and weak shielding 33 about the mast structure 30. p I prefer to use a rubber composition whichiis moldable and accordingly will grip the corrugations 31 formed on the inner surface of the metal shield 33 to hold the latter in place. Gas-expanded rubber which is of light weight and composedthe vehicle structure 3|. The bottom edge 33' of the shield 33 is spaced from the base to prevent grounding of the shield except through the high radio frequency impedance to be described.

The trailing edge 35-435 is not joined but is kept open in order to reduce the eddy-currents generated in the conductor 33. The conductor 33 is preferably of copper or aluminum material. The conductor 33. is connected to ground potential through a radio frequency choke 31 by connection leads 38. The rod ,orantenna wire 321s connected to the primary 40 of 'the antenna stage coupling transformer 4| by connection lead 32. The secondary 43 of the antenna transformer-4| is tuned by a variable condenser 44, the output. of which is connected to the radio frequency amplifier The reception by the vertical rod 32 is similar to that of any corresponding non-directional mast antenna for use at the radio receiver d5f'or communication or directional reception. I

The high velocity atmospheric particles impinging on the antenna wire 33 dissipate their electrical charges therein which electrical charges are conductedto ground through the ra-- dio frequency choke coil 31. Once the electrical charges are dissipated in the shield 33 and conducted to ground, the shield performs the neutralizing action on the electrically charged particles. The radio frequency signals pass through the shield 33 to the antenna rod 32 losing only a small amount of its energy due to the high radio frequency impedance of the shield 33 with respect to ground potential. The trailing edges 35 of the shield 33 minimizes any current losses induced in the shield by the radio frequency signal waves to increase the resultant shielding efficiency and increase the signal-to-static reception ratio by the antenna system. I prefer to make the radio frequency inductance of the primary 40 of the antenna transformer 41 of lower impedance value than the corresponding radio frequency impedance of the radio frequency choke coil' 31 connected to the shield 33. By maintaining such relative impedance ratio, namely maintaining the shield at a higher impedance with respect to the antenna 32, the degree of signal absorption by the shield 33 is further diminished.

To further increase the efliciency of the shield by minimizing eddy-current losses therein, the shield is slotted transversely with slots 46 as shown in Figure 3. Reduction of the eddy-current losses is accomplished by reducing the mean free electrical path in which any of the eddycurrents can now. and is performed by slotting the shield at different portions thereof. The slots 46 divide the shield into a corresponding plurality of segments 41. The segments 41 are electrically interconnected and the, connections shown at 48 serve this function.

To assist in the gripping action of the segments 41 of the shield upon the molded insulation core 36, I. prefer to crimp the slotted edges at regions 46 inwardly to form the crimped edges 43 for the shield segments 41. Figure 4 is an enlarged cross-sectional view taken along 4-4 of Figure 3 illustrating the preferred arrangement whereby the crimped edges 48 at'the slotted portions are set into the molded insulation material 36 and rigidly maintain the shielded structure in place.

In Figure 111 I illustrate a modification of the simpler antistatic non-directional antenna repreand to the left. The output of the radio receiver sented in Figure 1. This system comprises two opposed antenna masts 20 and 2| forming a nondirectional antenna. When the masts 26 and. 2|

are opposed and are of equal length they form a doublet antenna as is well known. This modification is independent of the relative lengths or positions of the masts 26 and 2|. Each of the masts 26 and 2| are enclosed by a metallic shield 22 and 23 respectively. Shields 22 and 23 are similar to the hereinabove described shield structure 33 enclosing antenna 32 of Figure 1. The

anti-static shield-s 22 and 23 are conductively connected to ground by their respective radio frequency choke coils 24 and 25.

The masts 26 and 2| are connected to the coupling coil winding 26. The center tap 21 of winding 26 is connected to ground potential. Antennae 26 and 2| form an efiective non-directional doublet the electrical neutral point 21 of which is connected to ground potential. The winding 26 may be replaced by a transmission line to the radio frequency amplifier 28 at a remote point. A tuned circuit 29 is shown coupled to the Winding 26 for selectively impressing radio signals induced in the antennae 262 on the radio frequency amplifier 26.

The non-directional antenna systems of Figures 1 and 1A may be employed for ordinary radio communication upon an aircraft or may be used as the non-directional antenna of a direction finding system. The metallic shields 22 and 23 conduct the changes of static electricity built up by the speed of the aircraft through rain, fog, dust and the like to ground. The electrical impulses are neutralized with respect to the antenna array 26'2| since the nodal or neutral point of the antenna is connected to ground. It is to be understood that the antenna array 262| is mechanically supported upon the aircraft. The antenna array 26-2| may be supported in a vertical position or any other position with respect to the aircraft such as a horizontal position. The system of Figure 1A is adapted to eliminate any static pulses to an even greater degree than the single mast modification of Figure 1.

Figure is a schematic illustration of a rightleft indicating radio direction finding system of one modification of my present system. This system utilizes a cardioid reception pattern produced by two spaced

mast antennae

56 and 5| The

masts

56 and 5| are anti-statically shielded by the

conductive shields

52 and 53 individually closing the antennae and connected to ground through the radio frequency choke coils 54 and 55 in a manner similar to the shielded antenna hereinabove described in connection with Figures 1 to 4. The size and spacing of

the'antennae

56 and 5| depend upon the type of vehicle or station it is installed upon and the frequency range it is operated upon. The

antennae

56 and 5| are conducted by

leads

56 and 51 to an intermediate position where the signals are combined in accordance with my present invention to produce the right and left cardioid reception patterns. A time-delaynetwork 58 is connected in series between either

antennae

56 or 5| and the primary 66 of th radio frequency coupling coil 6|, the

is correspondingly successively switched to the right and left sections of a differentially connected indicating meter 68 by switch 69 operating in synchronism with the switching system 64 to 61. The theory of the operation of my present invention may be better understood by the following description in connection with Figures 6 to 23:

In Figure 6 I illustrate the central summation -of signals from two spaced

vertical antennae

56 and 5|. The antenna coupling transformer 6| is connected at the mid-position of connection leads 56 and 51. The primary 66 of the transformer 6| has its mid-point connected to ground. The secondary 62 of the transformer 6| is connected to the input of the radio receiver 63. Figure 7 illustrates the polar reception pattern of the centrally summated spaced antenna system 565|. The polar ordinate at the angle 9 indicates the relative intensity of the output of the antenna array of Figure 6 in correspondence with the angle of incidence 9 of the radio signals as indicated in Figure 6. A centrally summated spaced mast system produces a figure-of-eight reception pattern having its null position perpendicular to the plane of the masts.

Figure 8 illustrates the summation of the signals from

masts

56 and 5| at the base of one of the antennae. The reception pattern with summation at the left antenna is shown inFiE- secondary 62 of which is connected to thei p ure 9 as a cardioid with its null position pointing toward the right and'lying in the plane of the masts.

Figure 10 illustrates the summation of the two mast signals at the base of the right antenna 5| producing the cardioid reception pattern illustrated in Figure 11 having its null position pointing toward the left in the plane of the

masts

56 and 5|. The reason for the null reception pattern produced by the antenna array of Figure 10, for example, is that the time-phase lag between the signals induced in the vertical mast 56 reaches the primary 66 of the antenna transformer 6| in exact time-phase with the incidence of the signals upon the mast 5|. Since the signals from the

antennae

56 and 5| are introduced apart at the primary winding 66, the eflects of signals in the plane of the antennae 565| coming from the left are nullified to produce the null shown in Figure 11. Signals originating from the right are impressed upon antenna 5| first and the time-phase displacement between the signals impressed upon the antenna 56 is twice that corresponding to the spacing between the

antennae

56 and 5| since it takes approximately equal time intervals for the radiant energy to traverse the space between the

antenna

56 and 5| as it takes for the electrical signals to travel across the conductor 56 between the second impressed antenna 56 and the primary wind-Y ing 66.

In Figures 12 and 14 are illustrated an antenna system and circuits having the antenna transformer 6| located centrally between the.

masts

56 and 5| and employing a time-delay network 58 to produce a resultant cardioid reception pattern. By placing the time-delay network 58 in the connection lead 51 from the right hand antenna 5|, the cardioid reception pattern illustrated in Figure 13 is produced with its null position toward theright corresponding to Figures 8 and 9. By placing the time-delay network in circuit with the lead 56 from the left antenna 50, the left hand cardioid pattern of Figure 15 is produced. The time-delay network 58 is designed to superimpose a time-phase displacement upon the antenna. signal conducted to the primary 6B of the transformer equivalent to the distance between the spaced

antenna

50 and 5|, namely the time consumed by the travel of the radiant energy between the two masts. With such a time-delay, the signals impressedfrom both ends upon the primary 58 will be substantially equal and of Opposite phase to produce the null as indicated by the illustrated-reception patterns.

In Figure 16 I have illustrated the double mast right-left indicating direction finding system employing the alternately switched time-delay network 58 with switching circuits 54 to 51 corresponding to the system of Figure 5. In place of the simple

vertical masts

50 and 5| I herein employ doublet antenna systems 58' and 5| coupled to the connectionieads 55 and 51. through coupling transformers I8 and H. The dipole antennae systems 50' and 5| are individually nondirectional in character and are particularly useful for ultra-high frequency reception. By combining them with the time-delay network to 'produce the alternate cardioid reception patterns in a manner to be described, an eflicient high frequency right-left indicating direction finder system is feasible.

Although the

dipole antenna structures

58 and 5| may be mounted upon a vehicle in a stationary position, they may be rotatably mounted thereon in a manner described in connection with my co-pending application Serial No. 139,142, filed April 2'7, 1937, as particularly illustrated therein in Figure 4. Thus the null position of such direction finder is adjustable by the operator.

The

switches

54, 55, 55 and 51 are alternately switched between their contacts from the solid position illustrated to the opposite position. The alternate switching of these switches connects the time-delay network 58 alternately in series between the antenna connection leads 55 and 51 and the primary 50 of the transformer 5|. The illustrated connections of the switches 54 to 51 connect the time-delay network 58 into the connection lead 55 corresponding to the left antenna system 58 to produce the left cardioid reception pattern 12 of Figure 17. Curve 12 corresponds to the cardioid produced by the system of Figure 14.

The alternate position of the switches 54 to 51 connects the time-delay network 58 into the connection lead .51 producing the right cardioid reception pattern 13 shown in dotted lines in Figure 17 corresponding to that produced by the system of Figure 12. Continuous alternate switching of the time-delay network into the left and right antenna connections correspondingly successively produces the left and right cardioid polar reception patterns 12 and I3.

The successive right and left cardioid reception patterns introduce a signal upon the input of radio receiver 63 of magnitude corresponding to the angle incidence o of the radio waves with respect to the plane of the antenna system. a In Figure 17, the angle 9 was shown to intercept the right and left cardloids to produce different relative magnitudes of input for a predetermined signal. As shown in Figure 5, the output of the radio receiver is correspondingly switched to the right and left sections of the differentially indicating meter 58 where the effects of the two types of polar reception patterns are algebraically summated to produce a resultant indication of the needle to the right or left in accordance with the respective intensities of the reception patterns.

In carrying out my pesent invention, I generate cardioid reception patterns solely dependent upon the geometric position of the antenna array used. By using the time-delay network 58 which is substantially independent of the signal frequencies used, a definite time-lag or phase displacement is introduced upon all signals passing therethrough. The phase, displacement is made to correspond to the actual spacing of the antennae so that all resultant signals introduced to the radio receiver 53 will have a cardioid polar receptionpattern.

In Figures 18 to 22, I have illustrated different forms for the time-delay network 58. In Figure 18, a distributed inductance 14 and 15 interconnected by a series of capacitances 15 produces an electrical long line or time-delay network between the input terminals 11 and output terminals 18. The characteristic impedance Z0 of such network is preferably designed equal to the impedance of the individual antennae and the coupling transformers in order to eliminate interference and reflections as well known in the electrical art. The time-delay network is designed along well known theory to be substantially distortionless and independent of frequency discrimination. At the high frequencies used, the attenuation constant isreadily made substantially negligible. The velocity propagation of the radio frequency currents through the network determines the time-phase displacement between the input and output terminals '|'||8. Figure 19 illustrates an alternative long line'or time-delay network composed of one inductance section 88 and aseries of capacitances 8|. Such a halfsection line is preferably used where one side is connected to ground as illustrated.

Figures 20 and 21 illustrate time-delay networks composed of lumped inductive and

capacitive elements

82 and 83 forming balanced and half-section time-delay networks corresponding to Figures 18 and 19 respectively. By using proper design constants for the respective inductances 82 and capacitances 83, a distortionless long line substantially independent of frequency and actuation characteristics can be designed for the frequency bands used for directional reception.

Figure 22 is a continuous long line formed of a conductor 84 centrally positioned within a shielded housing 85. The distributed capacitance, inductance, resistance and conductance of the transmission line 84--85 are proportioned to have the distortionless properties to form the timedelay network 58. By designing the long line 8485 into a flexible construction, it may be arranged into a form requiring a minimum of space.

Figure 23 illustrates the time-delay network corresponding to Figure 21 and having lumped inductance'elements 82 and capacitance 83 connected in circuit as the time-delay-network 58 of my right-left indicator system corresponding to Figures 5 and 16. The terminals 85--8l are patterns as described in' connection with Figure 17.

The time-delay network may be avoided where further antenna systems are not objectionable with respect to wind resistance, space, costand the like. When it is realized that a mast antenna even when streamlined offers a minimum aeronetwork hereinabove described is useful for producing a direction finder system with a minimum number of antennae masts. In Figure 24 is illustrated a right-left direction finder system using cardioid reception patterns produced by four vertical antenna arrays 90 and-9|, 92 and 93 and without using time-delay networks. The left antenna system 90-9I is summated by primary winding 94 at the base of antenna 9|, corresponding to the system described in connection with Figure 10 and produces a left hand cardioid reception pattern corresponding to Figure 11. The right antenna array 92-93 is summated by primary winding 95 at the base of antenna 92 corresponding to the system described in connection with Figure 8 and producing a right hand cardioid reception pattern corresponding to Figure 9. The

. secondary windings 96 and 91 of the two antenna arrays are successively introduced to the input of radio receiver 63 by the switch 98. The output of receiver 63 is alternately introduced to the right and left sections of the differential indicating meter 68 by switch 69 in the manner described in connection with Figure 5.

The cardioids produced by the antenna arrays 909I and 92-93 do not depend on a time-delay network, correspondingly simplifying the switching system and circuits for producing the alternate right and left cardioid reception patterns. The reception'patterns depend solely on the geometric arrangement of the antenna array and the angular position of the station and accordingly are not affected by the tuning or tem-' perature. variations or electrical parameter changes of the system. By rectifying the output of the radio receiver 63 to the extent of producing uni-directional current a sensitive direct cur-J rent differential meter 68 may be used to summate the effects of the alternate antenna signal outputs to produce the corresponding right or left.

lar to the plane of the antenna array corresponding to the arrow shown in Figure 17, the position where signals to the right or left will cause deflections of the indicator 68 by signals from that direction producing balanced or null indications. Although I have illustrated mechanical switching arrangement to simplify the theoretical discussion and disclosures of my present invention I prefer to employ electronic switching arrangements whereby the transients in the radio frequency networks and circuits are eliminated. Such electronic switch systems are well known in the art and are hereinafter described in connection with the double and triple mast system but may be equally well employed with the four mast system of Figure 24.

In Figure 25 is illustrated a vertical mast, cardioid reception pattern. right left indicating direction finder system employing the principles of my present invention and utilizing three vertical masts to produce the cardioids without timenately produce the right and left cardioid patterns of Figure 17. The central mast IN is used in place of the two central masts 9| and 92 of Figure 24 and is alternately switched to the

primary windings

94 and 95 connecting the left and right antenna masts I00 and I02 by switch I03. The secondary windings 96 and 91 are correspondingly connected to the input of radio receiver 63 by synchronous operation of the switch 98.

Figure 26 is a schematic diagram of a rightleft'indicator system similar to that of Figure 25. Three vertical masts I00, IOI and I02 are combined by means of eletronic switching in a manner similar to the mechanical switching example of Figure 25. Two diode rectifiers I05 and I06 are employed with circuit connections for electronically combining the signals of the antenna masts to successively form right and left cardi-, oid reception patterns at the input of radio receiver 63. The electronic switching frequency is preferably an audio frequency of the order of one hundred and forty cycles per second. The output of the radio receiver is electronically switched in synchronism with the antenna system by means of a third diode rectifier I01.

An audio frequency oscillator I08 comprising the triode I09 generates a current of frequency of the order of one hundred forty cycles. An iron core transformer IIll contains coils III and I I2 coupled to the grid and plate respectively of the triode I09. Secondary windings H3, H4 and H5 are wound on the transformer IIO to transmit the audio frequency generated at the transformer to the electronic rectifier tubes I05, I06 and I01, The elements a of the rectifier tubes I05 and I06 are connected to the terminal III; of the winding II3 through individual radio frequency choke coils III and H8. The I) ends of the rectifiers I05 and I06 are connected to the opposite terminal II9 of the winding H3 to individual radio frequency choke coils I20 and IN.

The opposite terminals H6 and II9 of the secondary winding 3 are out of phase with respect to each other and accordingly altemately render the a anodes and the b anodes conductive with respect to the cathodes of the rectifiers I05 and I06 in a manner familiar to those skilled in the art. I prefer to connect the caththat the electronic switching circuit is herewith presented schematically and specific biasing conditions of the cathode are omitted for simplicity but are understood by those skilled in the art. The function of the diode rectifiers I05 and- I06 is similar to the operation of the mechanical switches I03 and 98 of Figure 25' where mechanical switching is employed. In this example, however, the alternate conductive nature of the a anodes and the b anodes correspond to the alternate position of the switches 98 and I03 from the solid to the dotted position.

When the a anodes are conductive with respect to their cathodes, the signals from masts I00 and IM combine through the primary winding 94 and induce a cardioid. pattern in the secondary winding 96 which is conducted through the cathode I25 of rectifier I06 to the input of the radio receiver. The D anodes are nonconductive at this period and accordingly signals from mast I02 and transformer 95-91are ineffective. Conversely, when the b anodes are conductive, the reversed cardioid pattern from masts IOI-I02 combine at transformer 95-91 and actuate the input of radio receiver 63. The output of the radio receiver receiving the successive cardioid input voltages is synchronously switched between the left and right sections ofthe difierential indicator 68 through the rectifier II. The a anode of rectifier I 01 is connected to the right hand terminal I26 of winding H; the b anode, to the left hand terminal of winding Ill. The terminals I26 and I2! are maintained at similar alternating current voltage potential and 180 out of phase in order to render the a and b anodes of diode I01 alternately 'conductive and in synchronism of the a and b anodes of the antenna diodes I05 and I06. The alternate conductive nature of the a and b anodes of diode I01 permits the rectified cardioid pattern outputs from radio receiver 63 to flow through the differential meter 68 in a predetermined manner to produce an indication to the right or left in accordance with the position of the radio transmitter as will now be evident.

Although I prefer to illustrate the triple mast example with electronic switching, I do not wish to be limited thereto since the established principles of electronic switching may be employed.

in the four mast case corresponding to Figure 24 as well as to the two mast case of Figures 5, 16 and 23 employing the time delay network 58. The electronic switching renders the diode anodes successively conductive with respect to the common cathode and permits the conduction of the radio frequency currents at the antenna stage to be combined in a predetermined manner similar to the simplified showing with the mechanical switching illustrations.

Although I have illustrated preferred forms for carrying out my present invention, it is to be understood that modifications are feasible and I do not intend to be limited except as set forth in the following claims.

I claim:

1. A radio direction finder system comprising a first non-directional antenna; a second nondirectional antenna; means for combining the signal outputs of said first and second antennae to successively form difierently oriented polar cardioid reception patterns; an indicator; and means for producing right-left indications on said indicator in accordance with the relative position of the antennae with respect to the signal source.

2. A radio direction finder system comprising a first non-directional antenna; a second nondirectional antenna; means for combining the signal outputs of said first and second antennae and means for alternately delaying the outputs of said antennae with respect to each other to successively form differently oriented polar cardioid reception patterns, comprising a time delay network in. circuit with said antennae; an indicator; and means for producing right-left indications on said indicator in accordance with the relative position of the antennae with respect to thesignal source.

3. A radio direction finder system comprising a first non-directional antenna; a second nondirectional antenna; and means for combining the signal outputs of said first and second antennae to successively form differently oriented polar cardioid reception pattems,.a time delay network and switching means for alternately connecting said network in circuit with said first and second antennae.

4. A radio direction finder system comprising mast antenna; a radio receiver responsive to said antenna signals; an indicator connected to the output of said receiver; means for alternately combining the signal outputs of said first and second antennae to successively form differently oriented polar cardioid reception patterns and switching means for alternately connecting a time delay network in circuit with said first and second antennae; and means for correspondingly switching the output of said receiver at said indicator for producing right and left deflections in accordance with the direction of the signal transmitter with respect to the position of said antennae.

5. A radio direction finder system comprising a first vertical mast antenna; a second vertical mast antenna; a radio receiver responsive to said antenna signals; a differential indicating meter connected to the output of said receiver; and means for alternately combining the signal outputs of said first and second antennae and means for alternately delaying the outputs of said antennae with' respect to each other to successively form right and left oriented polar cardioid reception patterns comprising a time delay network.

6. A radio direction fin'der system comprising a first non-directional antenna; a second nondirectional antenna; a radio receiver responsive to said antenna signals; a differential indicating meter connected to the output of said receiver; means for combining the signal outputs of said first and second antennae to successively form right and-left oriented polar cardioid reception patterns comprising a time delay network and switching means for alternately connecting said network in circuit with said first and second antennae; and means for correspondingly switching the output of said receiver at said differential meter for producing right and left deflections in accordance with the direction of the signal transmitter with respect to the position of said antennae.

7. A radio direction finder system comprising a first non-directional antenna; a second nondirectional antenna; a radio receiver responsive to said antenna signals; an indicator. connected to the output of said receiver; means for combining the signal outputs of said first and second antennae to successively form differently oriented polar cardioid reception patterns comprising a time delay network and switching means for alternately connecting said network in circuit with said first and second antennae; and means for correspondingly switching the output of said receiver at said indicator for producing right and left deflections in accordance with the direction of the signal transmitter with respect to the position of said antennae.

8. In a right-left indicating direction finding system, a plurality of non-directional antennae; circuit connections extending from said antennae for combining the signals from said antennae to produce non-symmetrical polar patterns an indicator connected to said circuit connections: and means whereby said indicator is alternately controlled by signals forming said patterns to produce right-left indications in accordance with the relative position of the antennae with respect to the signal source.

v 9. In a right-left indicating direction finding system, a plurality of non-directional antennae in spaced relation: means for combining the signals intercepted by said antennae to produce alternate reversed non-symmetrical polar patterns; an indicator and means for alternately applying the signals forming each of said patterns to said indicator; and means whereby said indicator operates in response to said signals for producing right-left indications in accordance with the relative position of the antennae with respect to the signal source.

10. In a right-left indicating direction finding system, a plurality of non-directional antennae in spaced relation; means for combining the signals intercepted by said antennae to produce alternate reversed non-symmetrical polar patterns; an indicator and means for alternately applying the signals forming each of said patterns to said indicator; and means whereby said indicator operates in response to said signals for producing right-left indications in accordance with the relative position of the antennae with respect to the signal source and in accordance with the sense of said signals.

11. In a right-left indicating direction finding system; a plurality of antennae in predetermined spaced relation; a time delay network having a time delay characteristic in accordance with the spatial relation of said antennae; an indicator; circuit connections to said indicator; and switching means for interposing said time delay network between said circuit connections and each of said antennae successively and for simultaneously connecting the other of said antennae in circuit with said circuit connections.

12. In a right-left indicating direction finding system; a plurality of antennae in predetermined spaced relation; a time delay network having a time delay characteristic in accordance with the spatial relation of said antennae; said network being connected in series with said antennae; an indicator; circuit connections from said indicator to said antennae circuit; and switching means for successively switching said time delay network between each of said antennae and said circuit connections.

' 13. In a right-left indicating direction finding system; a plurality of antennae in predetermined spaced relation; a time delay network having a time delaycharacteristic in accordance with the spatial relation of said antennae; said network being connected in series with said antennae; an indicator; circuit connections from said indicator to said antennae circuit; switching means for successively switching said time delay network between each of said antennae and said' circuit connections; and switching means for correspondingly successively reversing said indicator with respect to said circuit connections.

14. In a right-left indicating direction finding system; a plurality of antennae in predetermined spaced relation; 2 time delay network having a time delay characteristic in accordance with the spatial relation of said antennae; said network being connected in series with said antennae; a translating means connected in said series circuit; and switching means for switching said time delay network between each of said antennae and said translating means successively for producing .a plurality of non-symmetrical polar patterns.

15. In a right-left indicating direction finding system; a plurality of antennae in predetermined spaced relation; a time delay network having a time delay characteristic in accordance with the spa ial relation of said antennae; said network being connected in series with said antennae; a translating means connected in said series circuit; switching means for switching said time delay network between each of said antennae and said translating means successively for producing a plurality of non-symmetrical polar patterns; an indicator; circuit connections from said indicator to said translating means; and means whereby said indicator operates to indicate the relative position of the antennae with respect to the signal source.

16. In a right-left indicating direction finding system; a plurality of non-directional antennae in spaced relation; an indicator; means for producing cardioid patterns by means of said antennae in accordance with the orientation thereof switching means for reversing said patterns; means for alternately impressing said signals on said indicator to indicate to the right or left of the direction of the incident signal, depending upon the angular position of the plane of the antennae with respect to the signal source.

EDWARD J. HEFELE.